1894 lines
76 KiB
Rust
1894 lines
76 KiB
Rust
use crate::check::FnCtxt;
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use rustc_ast as ast;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
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use rustc_hir as hir;
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use rustc_hir::def::{CtorKind, DefKind, Res};
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use rustc_hir::pat_util::EnumerateAndAdjustIterator;
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use rustc_hir::{HirId, Pat, PatKind};
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use rustc_infer::infer;
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use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use rustc_middle::ty::subst::GenericArg;
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use rustc_middle::ty::{self, Adt, BindingMode, Ty, TypeFoldable};
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use rustc_span::hygiene::DesugaringKind;
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use rustc_span::lev_distance::find_best_match_for_name;
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use rustc_span::source_map::{Span, Spanned};
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use rustc_span::symbol::Ident;
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use rustc_span::{BytePos, DUMMY_SP};
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use rustc_trait_selection::traits::{ObligationCause, Pattern};
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use ty::VariantDef;
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use std::cmp;
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use std::collections::hash_map::Entry::{Occupied, Vacant};
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use super::report_unexpected_variant_res;
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const CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ: &str = "\
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This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a \
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pattern. Every trait defines a type, but because the size of trait implementors isn't fixed, \
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this type has no compile-time size. Therefore, all accesses to trait types must be through \
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pointers. If you encounter this error you should try to avoid dereferencing the pointer.
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You can read more about trait objects in the Trait Objects section of the Reference: \
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https://doc.rust-lang.org/reference/types.html#trait-objects";
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/// Information about the expected type at the top level of type checking a pattern.
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///
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/// **NOTE:** This is only for use by diagnostics. Do NOT use for type checking logic!
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#[derive(Copy, Clone)]
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struct TopInfo<'tcx> {
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/// The `expected` type at the top level of type checking a pattern.
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expected: Ty<'tcx>,
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/// Was the origin of the `span` from a scrutinee expression?
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///
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/// Otherwise there is no scrutinee and it could be e.g. from the type of a formal parameter.
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origin_expr: bool,
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/// The span giving rise to the `expected` type, if one could be provided.
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///
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/// If `origin_expr` is `true`, then this is the span of the scrutinee as in:
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///
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/// - `match scrutinee { ... }`
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/// - `let _ = scrutinee;`
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///
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/// This is used to point to add context in type errors.
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/// In the following example, `span` corresponds to the `a + b` expression:
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///
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/// ```text
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/// error[E0308]: mismatched types
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/// --> src/main.rs:L:C
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/// |
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/// L | let temp: usize = match a + b {
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/// | ----- this expression has type `usize`
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/// L | Ok(num) => num,
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/// | ^^^^^^^ expected `usize`, found enum `std::result::Result`
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/// |
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/// = note: expected type `usize`
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/// found type `std::result::Result<_, _>`
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/// ```
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span: Option<Span>,
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/// This refers to the parent pattern. Used to provide extra diagnostic information on errors.
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/// ```text
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/// error[E0308]: mismatched types
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/// --> $DIR/const-in-struct-pat.rs:8:17
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/// |
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/// L | struct f;
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/// | --------- unit struct defined here
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/// ...
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/// L | let Thing { f } = t;
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/// | ^
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/// | |
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/// | expected struct `std::string::String`, found struct `f`
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/// | `f` is interpreted as a unit struct, not a new binding
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/// | help: bind the struct field to a different name instead: `f: other_f`
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/// ```
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parent_pat: Option<&'tcx Pat<'tcx>>,
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}
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impl<'tcx> FnCtxt<'_, 'tcx> {
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fn pattern_cause(&self, ti: TopInfo<'tcx>, cause_span: Span) -> ObligationCause<'tcx> {
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let code = Pattern { span: ti.span, root_ty: ti.expected, origin_expr: ti.origin_expr };
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self.cause(cause_span, code)
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}
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fn demand_eqtype_pat_diag(
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&self,
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cause_span: Span,
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expected: Ty<'tcx>,
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actual: Ty<'tcx>,
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ti: TopInfo<'tcx>,
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) -> Option<DiagnosticBuilder<'tcx>> {
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self.demand_eqtype_with_origin(&self.pattern_cause(ti, cause_span), expected, actual)
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}
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fn demand_eqtype_pat(
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&self,
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cause_span: Span,
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expected: Ty<'tcx>,
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actual: Ty<'tcx>,
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ti: TopInfo<'tcx>,
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) {
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if let Some(mut err) = self.demand_eqtype_pat_diag(cause_span, expected, actual, ti) {
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err.emit();
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}
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}
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}
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const INITIAL_BM: BindingMode = BindingMode::BindByValue(hir::Mutability::Not);
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/// Mode for adjusting the expected type and binding mode.
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enum AdjustMode {
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/// Peel off all immediate reference types.
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Peel,
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/// Reset binding mode to the initial mode.
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Reset,
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/// Pass on the input binding mode and expected type.
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Pass,
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}
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impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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/// Type check the given top level pattern against the `expected` type.
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///
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/// If a `Some(span)` is provided and `origin_expr` holds,
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/// then the `span` represents the scrutinee's span.
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/// The scrutinee is found in e.g. `match scrutinee { ... }` and `let pat = scrutinee;`.
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///
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/// Otherwise, `Some(span)` represents the span of a type expression
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/// which originated the `expected` type.
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pub fn check_pat_top(
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&self,
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pat: &'tcx Pat<'tcx>,
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expected: Ty<'tcx>,
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span: Option<Span>,
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origin_expr: bool,
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) {
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let info = TopInfo { expected, origin_expr, span, parent_pat: None };
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self.check_pat(pat, expected, INITIAL_BM, info);
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}
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/// Type check the given `pat` against the `expected` type
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/// with the provided `def_bm` (default binding mode).
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///
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/// Outside of this module, `check_pat_top` should always be used.
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/// Conversely, inside this module, `check_pat_top` should never be used.
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#[instrument(level = "debug", skip(self, ti))]
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fn check_pat(
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&self,
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pat: &'tcx Pat<'tcx>,
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expected: Ty<'tcx>,
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def_bm: BindingMode,
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ti: TopInfo<'tcx>,
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) {
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let path_res = match &pat.kind {
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PatKind::Path(qpath) => Some(self.resolve_ty_and_res_ufcs(qpath, pat.hir_id, pat.span)),
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_ => None,
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};
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let adjust_mode = self.calc_adjust_mode(pat, path_res.map(|(res, ..)| res));
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let (expected, def_bm) = self.calc_default_binding_mode(pat, expected, def_bm, adjust_mode);
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let ty = match pat.kind {
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PatKind::Wild => expected,
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PatKind::Lit(lt) => self.check_pat_lit(pat.span, lt, expected, ti),
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PatKind::Range(lhs, rhs, _) => self.check_pat_range(pat.span, lhs, rhs, expected, ti),
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PatKind::Binding(ba, var_id, _, sub) => {
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self.check_pat_ident(pat, ba, var_id, sub, expected, def_bm, ti)
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}
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PatKind::TupleStruct(ref qpath, subpats, ddpos) => {
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self.check_pat_tuple_struct(pat, qpath, subpats, ddpos, expected, def_bm, ti)
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}
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PatKind::Path(_) => self.check_pat_path(pat, path_res.unwrap(), expected, ti),
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PatKind::Struct(ref qpath, fields, etc) => {
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self.check_pat_struct(pat, qpath, fields, etc, expected, def_bm, ti)
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}
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PatKind::Or(pats) => {
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let parent_pat = Some(pat);
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for pat in pats {
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self.check_pat(pat, expected, def_bm, TopInfo { parent_pat, ..ti });
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}
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expected
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}
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PatKind::Tuple(elements, ddpos) => {
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self.check_pat_tuple(pat.span, elements, ddpos, expected, def_bm, ti)
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}
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PatKind::Box(inner) => self.check_pat_box(pat.span, inner, expected, def_bm, ti),
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PatKind::Ref(inner, mutbl) => {
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self.check_pat_ref(pat, inner, mutbl, expected, def_bm, ti)
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}
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PatKind::Slice(before, slice, after) => {
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self.check_pat_slice(pat.span, before, slice, after, expected, def_bm, ti)
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}
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};
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self.write_ty(pat.hir_id, ty);
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// (note_1): In most of the cases where (note_1) is referenced
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// (literals and constants being the exception), we relate types
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// using strict equality, even though subtyping would be sufficient.
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// There are a few reasons for this, some of which are fairly subtle
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// and which cost me (nmatsakis) an hour or two debugging to remember,
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// so I thought I'd write them down this time.
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//
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// 1. There is no loss of expressiveness here, though it does
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// cause some inconvenience. What we are saying is that the type
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// of `x` becomes *exactly* what is expected. This can cause unnecessary
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// errors in some cases, such as this one:
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//
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// ```
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// fn foo<'x>(x: &'x i32) {
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// let a = 1;
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// let mut z = x;
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// z = &a;
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// }
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// ```
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//
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// The reason we might get an error is that `z` might be
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// assigned a type like `&'x i32`, and then we would have
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// a problem when we try to assign `&a` to `z`, because
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// the lifetime of `&a` (i.e., the enclosing block) is
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// shorter than `'x`.
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//
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// HOWEVER, this code works fine. The reason is that the
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// expected type here is whatever type the user wrote, not
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// the initializer's type. In this case the user wrote
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// nothing, so we are going to create a type variable `Z`.
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// Then we will assign the type of the initializer (`&'x i32`)
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// as a subtype of `Z`: `&'x i32 <: Z`. And hence we
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// will instantiate `Z` as a type `&'0 i32` where `'0` is
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// a fresh region variable, with the constraint that `'x : '0`.
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// So basically we're all set.
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//
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// Note that there are two tests to check that this remains true
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// (`regions-reassign-{match,let}-bound-pointer.rs`).
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//
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// 2. Things go horribly wrong if we use subtype. The reason for
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// THIS is a fairly subtle case involving bound regions. See the
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// `givens` field in `region_constraints`, as well as the test
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// `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
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// for details. Short version is that we must sometimes detect
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// relationships between specific region variables and regions
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// bound in a closure signature, and that detection gets thrown
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// off when we substitute fresh region variables here to enable
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// subtyping.
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}
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/// Compute the new expected type and default binding mode from the old ones
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/// as well as the pattern form we are currently checking.
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fn calc_default_binding_mode(
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&self,
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pat: &'tcx Pat<'tcx>,
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expected: Ty<'tcx>,
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def_bm: BindingMode,
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adjust_mode: AdjustMode,
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) -> (Ty<'tcx>, BindingMode) {
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match adjust_mode {
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AdjustMode::Pass => (expected, def_bm),
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AdjustMode::Reset => (expected, INITIAL_BM),
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AdjustMode::Peel => self.peel_off_references(pat, expected, def_bm),
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}
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}
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/// How should the binding mode and expected type be adjusted?
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///
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/// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`.
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fn calc_adjust_mode(&self, pat: &'tcx Pat<'tcx>, opt_path_res: Option<Res>) -> AdjustMode {
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// When we perform destructuring assignment, we disable default match bindings, which are
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// unintuitive in this context.
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if !pat.default_binding_modes {
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return AdjustMode::Reset;
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}
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match &pat.kind {
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// Type checking these product-like types successfully always require
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// that the expected type be of those types and not reference types.
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PatKind::Struct(..)
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| PatKind::TupleStruct(..)
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| PatKind::Tuple(..)
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| PatKind::Box(_)
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| PatKind::Range(..)
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| PatKind::Slice(..) => AdjustMode::Peel,
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// String and byte-string literals result in types `&str` and `&[u8]` respectively.
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// All other literals result in non-reference types.
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// As a result, we allow `if let 0 = &&0 {}` but not `if let "foo" = &&"foo {}`.
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PatKind::Lit(lt) => match self.check_expr(lt).kind() {
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ty::Ref(..) => AdjustMode::Pass,
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_ => AdjustMode::Peel,
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},
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PatKind::Path(_) => match opt_path_res.unwrap() {
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// These constants can be of a reference type, e.g. `const X: &u8 = &0;`.
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// Peeling the reference types too early will cause type checking failures.
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// Although it would be possible to *also* peel the types of the constants too.
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Res::Def(DefKind::Const | DefKind::AssocConst, _) => AdjustMode::Pass,
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// In the `ValueNS`, we have `SelfCtor(..) | Ctor(_, Const), _)` remaining which
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// could successfully compile. The former being `Self` requires a unit struct.
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// In either case, and unlike constants, the pattern itself cannot be
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// a reference type wherefore peeling doesn't give up any expressivity.
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_ => AdjustMode::Peel,
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},
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// When encountering a `& mut? pat` pattern, reset to "by value".
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// This is so that `x` and `y` here are by value, as they appear to be:
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//
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// ```
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// match &(&22, &44) {
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// (&x, &y) => ...
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// }
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// ```
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//
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// See issue #46688.
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PatKind::Ref(..) => AdjustMode::Reset,
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// A `_` pattern works with any expected type, so there's no need to do anything.
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PatKind::Wild
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// Bindings also work with whatever the expected type is,
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// and moreover if we peel references off, that will give us the wrong binding type.
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// Also, we can have a subpattern `binding @ pat`.
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// Each side of the `@` should be treated independently (like with OR-patterns).
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| PatKind::Binding(..)
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// An OR-pattern just propagates to each individual alternative.
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// This is maximally flexible, allowing e.g., `Some(mut x) | &Some(mut x)`.
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// In that example, `Some(mut x)` results in `Peel` whereas `&Some(mut x)` in `Reset`.
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| PatKind::Or(_) => AdjustMode::Pass,
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}
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}
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/// Peel off as many immediately nested `& mut?` from the expected type as possible
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/// and return the new expected type and binding default binding mode.
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/// The adjustments vector, if non-empty is stored in a table.
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fn peel_off_references(
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&self,
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pat: &'tcx Pat<'tcx>,
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expected: Ty<'tcx>,
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mut def_bm: BindingMode,
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) -> (Ty<'tcx>, BindingMode) {
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let mut expected = self.resolve_vars_with_obligations(&expected);
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// Peel off as many `&` or `&mut` from the scrutinee type as possible. For example,
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// for `match &&&mut Some(5)` the loop runs three times, aborting when it reaches
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// the `Some(5)` which is not of type Ref.
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//
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// For each ampersand peeled off, update the binding mode and push the original
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// type into the adjustments vector.
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//
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// See the examples in `ui/match-defbm*.rs`.
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let mut pat_adjustments = vec![];
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while let ty::Ref(_, inner_ty, inner_mutability) = *expected.kind() {
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debug!("inspecting {:?}", expected);
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debug!("current discriminant is Ref, inserting implicit deref");
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// Preserve the reference type. We'll need it later during THIR lowering.
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pat_adjustments.push(expected);
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expected = inner_ty;
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def_bm = ty::BindByReference(match def_bm {
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// If default binding mode is by value, make it `ref` or `ref mut`
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// (depending on whether we observe `&` or `&mut`).
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ty::BindByValue(_) |
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// When `ref mut`, stay a `ref mut` (on `&mut`) or downgrade to `ref` (on `&`).
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ty::BindByReference(hir::Mutability::Mut) => inner_mutability,
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// Once a `ref`, always a `ref`.
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// This is because a `& &mut` cannot mutate the underlying value.
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ty::BindByReference(m @ hir::Mutability::Not) => m,
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});
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}
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if !pat_adjustments.is_empty() {
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debug!("default binding mode is now {:?}", def_bm);
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self.inh
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.typeck_results
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.borrow_mut()
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.pat_adjustments_mut()
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.insert(pat.hir_id, pat_adjustments);
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}
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(expected, def_bm)
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}
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fn check_pat_lit(
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&self,
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span: Span,
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lt: &hir::Expr<'tcx>,
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expected: Ty<'tcx>,
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ti: TopInfo<'tcx>,
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) -> Ty<'tcx> {
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// We've already computed the type above (when checking for a non-ref pat),
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// so avoid computing it again.
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let ty = self.node_ty(lt.hir_id);
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// Byte string patterns behave the same way as array patterns
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// They can denote both statically and dynamically-sized byte arrays.
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let mut pat_ty = ty;
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if let hir::ExprKind::Lit(Spanned { node: ast::LitKind::ByteStr(_), .. }) = lt.kind {
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let expected = self.structurally_resolved_type(span, expected);
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if let ty::Ref(_, inner_ty, _) = expected.kind() {
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if matches!(inner_ty.kind(), ty::Slice(_)) {
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let tcx = self.tcx;
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trace!(?lt.hir_id.local_id, "polymorphic byte string lit");
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self.typeck_results
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.borrow_mut()
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.treat_byte_string_as_slice
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.insert(lt.hir_id.local_id);
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pat_ty = tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_slice(tcx.types.u8));
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}
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}
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}
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|
|
// Somewhat surprising: in this case, the subtyping relation goes the
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// opposite way as the other cases. Actually what we really want is not
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// a subtyping relation at all but rather that there exists a LUB
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// (so that they can be compared). However, in practice, constants are
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// always scalars or strings. For scalars subtyping is irrelevant,
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// and for strings `ty` is type is `&'static str`, so if we say that
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//
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// &'static str <: expected
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//
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// then that's equivalent to there existing a LUB.
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let cause = self.pattern_cause(ti, span);
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if let Some(mut err) = self.demand_suptype_with_origin(&cause, expected, pat_ty) {
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err.emit_unless(
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ti.span
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.filter(|&s| {
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// In the case of `if`- and `while`-expressions we've already checked
|
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// that `scrutinee: bool`. We know that the pattern is `true`,
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// so an error here would be a duplicate and from the wrong POV.
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s.is_desugaring(DesugaringKind::CondTemporary)
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})
|
|
.is_some(),
|
|
);
|
|
}
|
|
|
|
pat_ty
|
|
}
|
|
|
|
fn check_pat_range(
|
|
&self,
|
|
span: Span,
|
|
lhs: Option<&'tcx hir::Expr<'tcx>>,
|
|
rhs: Option<&'tcx hir::Expr<'tcx>>,
|
|
expected: Ty<'tcx>,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let calc_side = |opt_expr: Option<&'tcx hir::Expr<'tcx>>| match opt_expr {
|
|
None => (None, None),
|
|
Some(expr) => {
|
|
let ty = self.check_expr(expr);
|
|
// Check that the end-point is of numeric or char type.
|
|
let fail = !(ty.is_numeric() || ty.is_char() || ty.references_error());
|
|
(Some(ty), Some((fail, ty, expr.span)))
|
|
}
|
|
};
|
|
let (lhs_ty, lhs) = calc_side(lhs);
|
|
let (rhs_ty, rhs) = calc_side(rhs);
|
|
|
|
if let (Some((true, ..)), _) | (_, Some((true, ..))) = (lhs, rhs) {
|
|
// There exists a side that didn't meet our criteria that the end-point
|
|
// be of a numeric or char type, as checked in `calc_side` above.
|
|
self.emit_err_pat_range(span, lhs, rhs);
|
|
return self.tcx.ty_error();
|
|
}
|
|
|
|
// Now that we know the types can be unified we find the unified type
|
|
// and use it to type the entire expression.
|
|
let common_type = self.resolve_vars_if_possible(lhs_ty.or(rhs_ty).unwrap_or(expected));
|
|
|
|
// Subtyping doesn't matter here, as the value is some kind of scalar.
|
|
let demand_eqtype = |x, y| {
|
|
if let Some((_, x_ty, x_span)) = x {
|
|
if let Some(mut err) = self.demand_eqtype_pat_diag(x_span, expected, x_ty, ti) {
|
|
if let Some((_, y_ty, y_span)) = y {
|
|
self.endpoint_has_type(&mut err, y_span, y_ty);
|
|
}
|
|
err.emit();
|
|
};
|
|
}
|
|
};
|
|
demand_eqtype(lhs, rhs);
|
|
demand_eqtype(rhs, lhs);
|
|
|
|
common_type
|
|
}
|
|
|
|
fn endpoint_has_type(&self, err: &mut DiagnosticBuilder<'_>, span: Span, ty: Ty<'_>) {
|
|
if !ty.references_error() {
|
|
err.span_label(span, &format!("this is of type `{}`", ty));
|
|
}
|
|
}
|
|
|
|
fn emit_err_pat_range(
|
|
&self,
|
|
span: Span,
|
|
lhs: Option<(bool, Ty<'tcx>, Span)>,
|
|
rhs: Option<(bool, Ty<'tcx>, Span)>,
|
|
) {
|
|
let span = match (lhs, rhs) {
|
|
(Some((true, ..)), Some((true, ..))) => span,
|
|
(Some((true, _, sp)), _) => sp,
|
|
(_, Some((true, _, sp))) => sp,
|
|
_ => span_bug!(span, "emit_err_pat_range: no side failed or exists but still error?"),
|
|
};
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0029,
|
|
"only `char` and numeric types are allowed in range patterns"
|
|
);
|
|
let msg = |ty| format!("this is of type `{}` but it should be `char` or numeric", ty);
|
|
let mut one_side_err = |first_span, first_ty, second: Option<(bool, Ty<'tcx>, Span)>| {
|
|
err.span_label(first_span, &msg(first_ty));
|
|
if let Some((_, ty, sp)) = second {
|
|
self.endpoint_has_type(&mut err, sp, ty);
|
|
}
|
|
};
|
|
match (lhs, rhs) {
|
|
(Some((true, lhs_ty, lhs_sp)), Some((true, rhs_ty, rhs_sp))) => {
|
|
err.span_label(lhs_sp, &msg(lhs_ty));
|
|
err.span_label(rhs_sp, &msg(rhs_ty));
|
|
}
|
|
(Some((true, lhs_ty, lhs_sp)), rhs) => one_side_err(lhs_sp, lhs_ty, rhs),
|
|
(lhs, Some((true, rhs_ty, rhs_sp))) => one_side_err(rhs_sp, rhs_ty, lhs),
|
|
_ => span_bug!(span, "Impossible, verified above."),
|
|
}
|
|
if self.tcx.sess.teach(&err.get_code().unwrap()) {
|
|
err.note(
|
|
"In a match expression, only numbers and characters can be matched \
|
|
against a range. This is because the compiler checks that the range \
|
|
is non-empty at compile-time, and is unable to evaluate arbitrary \
|
|
comparison functions. If you want to capture values of an orderable \
|
|
type between two end-points, you can use a guard.",
|
|
);
|
|
}
|
|
err.emit();
|
|
}
|
|
|
|
fn check_pat_ident(
|
|
&self,
|
|
pat: &'tcx Pat<'tcx>,
|
|
ba: hir::BindingAnnotation,
|
|
var_id: HirId,
|
|
sub: Option<&'tcx Pat<'tcx>>,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
// Determine the binding mode...
|
|
let bm = match ba {
|
|
hir::BindingAnnotation::Unannotated => def_bm,
|
|
_ => BindingMode::convert(ba),
|
|
};
|
|
// ...and store it in a side table:
|
|
self.inh.typeck_results.borrow_mut().pat_binding_modes_mut().insert(pat.hir_id, bm);
|
|
|
|
debug!("check_pat_ident: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
|
|
|
|
let local_ty = self.local_ty(pat.span, pat.hir_id).decl_ty;
|
|
let eq_ty = match bm {
|
|
ty::BindByReference(mutbl) => {
|
|
// If the binding is like `ref x | ref mut x`,
|
|
// then `x` is assigned a value of type `&M T` where M is the
|
|
// mutability and T is the expected type.
|
|
//
|
|
// `x` is assigned a value of type `&M T`, hence `&M T <: typeof(x)`
|
|
// is required. However, we use equality, which is stronger.
|
|
// See (note_1) for an explanation.
|
|
self.new_ref_ty(pat.span, mutbl, expected)
|
|
}
|
|
// Otherwise, the type of x is the expected type `T`.
|
|
ty::BindByValue(_) => {
|
|
// As above, `T <: typeof(x)` is required, but we use equality, see (note_1).
|
|
expected
|
|
}
|
|
};
|
|
self.demand_eqtype_pat(pat.span, eq_ty, local_ty, ti);
|
|
|
|
// If there are multiple arms, make sure they all agree on
|
|
// what the type of the binding `x` ought to be.
|
|
if var_id != pat.hir_id {
|
|
self.check_binding_alt_eq_ty(pat.span, var_id, local_ty, ti);
|
|
}
|
|
|
|
if let Some(p) = sub {
|
|
self.check_pat(&p, expected, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
|
|
}
|
|
|
|
local_ty
|
|
}
|
|
|
|
fn check_binding_alt_eq_ty(&self, span: Span, var_id: HirId, ty: Ty<'tcx>, ti: TopInfo<'tcx>) {
|
|
let var_ty = self.local_ty(span, var_id).decl_ty;
|
|
if let Some(mut err) = self.demand_eqtype_pat_diag(span, var_ty, ty, ti) {
|
|
let hir = self.tcx.hir();
|
|
let var_ty = self.resolve_vars_with_obligations(var_ty);
|
|
let msg = format!("first introduced with type `{}` here", var_ty);
|
|
err.span_label(hir.span(var_id), msg);
|
|
let in_match = hir.parent_iter(var_id).any(|(_, n)| {
|
|
matches!(
|
|
n,
|
|
hir::Node::Expr(hir::Expr {
|
|
kind: hir::ExprKind::Match(.., hir::MatchSource::Normal),
|
|
..
|
|
})
|
|
)
|
|
});
|
|
let pre = if in_match { "in the same arm, " } else { "" };
|
|
err.note(&format!("{}a binding must have the same type in all alternatives", pre));
|
|
err.emit();
|
|
}
|
|
}
|
|
|
|
fn borrow_pat_suggestion(
|
|
&self,
|
|
err: &mut DiagnosticBuilder<'_>,
|
|
pat: &Pat<'_>,
|
|
inner: &Pat<'_>,
|
|
expected: Ty<'tcx>,
|
|
) {
|
|
let tcx = self.tcx;
|
|
if let PatKind::Binding(..) = inner.kind {
|
|
let binding_parent_id = tcx.hir().get_parent_node(pat.hir_id);
|
|
let binding_parent = tcx.hir().get(binding_parent_id);
|
|
debug!("inner {:?} pat {:?} parent {:?}", inner, pat, binding_parent);
|
|
match binding_parent {
|
|
hir::Node::Param(hir::Param { span, .. }) => {
|
|
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(inner.span) {
|
|
err.span_suggestion(
|
|
*span,
|
|
&format!("did you mean `{}`", snippet),
|
|
format!(" &{}", expected),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
}
|
|
hir::Node::Arm(_) | hir::Node::Pat(_) => {
|
|
// rely on match ergonomics or it might be nested `&&pat`
|
|
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(inner.span) {
|
|
err.span_suggestion(
|
|
pat.span,
|
|
"you can probably remove the explicit borrow",
|
|
snippet,
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
}
|
|
}
|
|
_ => {} // don't provide suggestions in other cases #55175
|
|
}
|
|
}
|
|
}
|
|
|
|
pub fn check_dereferenceable(&self, span: Span, expected: Ty<'tcx>, inner: &Pat<'_>) -> bool {
|
|
if let PatKind::Binding(..) = inner.kind {
|
|
if let Some(mt) = self.shallow_resolve(expected).builtin_deref(true) {
|
|
if let ty::Dynamic(..) = mt.ty.kind() {
|
|
// This is "x = SomeTrait" being reduced from
|
|
// "let &x = &SomeTrait" or "let box x = Box<SomeTrait>", an error.
|
|
let type_str = self.ty_to_string(expected);
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0033,
|
|
"type `{}` cannot be dereferenced",
|
|
type_str
|
|
);
|
|
err.span_label(span, format!("type `{}` cannot be dereferenced", type_str));
|
|
if self.tcx.sess.teach(&err.get_code().unwrap()) {
|
|
err.note(CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ);
|
|
}
|
|
err.emit();
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
true
|
|
}
|
|
|
|
fn check_pat_struct(
|
|
&self,
|
|
pat: &'tcx Pat<'tcx>,
|
|
qpath: &hir::QPath<'_>,
|
|
fields: &'tcx [hir::PatField<'tcx>],
|
|
etc: bool,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
// Resolve the path and check the definition for errors.
|
|
let (variant, pat_ty) = if let Some(variant_ty) = self.check_struct_path(qpath, pat.hir_id)
|
|
{
|
|
variant_ty
|
|
} else {
|
|
let err = self.tcx.ty_error();
|
|
for field in fields {
|
|
let ti = TopInfo { parent_pat: Some(&pat), ..ti };
|
|
self.check_pat(&field.pat, err, def_bm, ti);
|
|
}
|
|
return err;
|
|
};
|
|
|
|
// Type-check the path.
|
|
self.demand_eqtype_pat(pat.span, expected, pat_ty, ti);
|
|
|
|
// Type-check subpatterns.
|
|
if self.check_struct_pat_fields(pat_ty, &pat, variant, fields, etc, def_bm, ti) {
|
|
pat_ty
|
|
} else {
|
|
self.tcx.ty_error()
|
|
}
|
|
}
|
|
|
|
fn check_pat_path(
|
|
&self,
|
|
pat: &Pat<'_>,
|
|
path_resolution: (Res, Option<Ty<'tcx>>, &'b [hir::PathSegment<'b>]),
|
|
expected: Ty<'tcx>,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let tcx = self.tcx;
|
|
|
|
// We have already resolved the path.
|
|
let (res, opt_ty, segments) = path_resolution;
|
|
match res {
|
|
Res::Err => {
|
|
self.set_tainted_by_errors();
|
|
return tcx.ty_error();
|
|
}
|
|
Res::Def(DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fictive | CtorKind::Fn), _) => {
|
|
report_unexpected_variant_res(tcx, res, pat.span);
|
|
return tcx.ty_error();
|
|
}
|
|
Res::SelfCtor(..)
|
|
| Res::Def(
|
|
DefKind::Ctor(_, CtorKind::Const)
|
|
| DefKind::Const
|
|
| DefKind::AssocConst
|
|
| DefKind::ConstParam,
|
|
_,
|
|
) => {} // OK
|
|
_ => bug!("unexpected pattern resolution: {:?}", res),
|
|
}
|
|
|
|
// Type-check the path.
|
|
let (pat_ty, pat_res) =
|
|
self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id);
|
|
if let Some(err) =
|
|
self.demand_suptype_with_origin(&self.pattern_cause(ti, pat.span), expected, pat_ty)
|
|
{
|
|
self.emit_bad_pat_path(err, pat.span, res, pat_res, pat_ty, segments, ti.parent_pat);
|
|
}
|
|
pat_ty
|
|
}
|
|
|
|
fn maybe_suggest_range_literal(
|
|
&self,
|
|
e: &mut DiagnosticBuilder<'_>,
|
|
opt_def_id: Option<hir::def_id::DefId>,
|
|
ident: Ident,
|
|
) -> bool {
|
|
match opt_def_id {
|
|
Some(def_id) => match self.tcx.hir().get_if_local(def_id) {
|
|
Some(hir::Node::Item(hir::Item {
|
|
kind: hir::ItemKind::Const(_, body_id), ..
|
|
})) => match self.tcx.hir().get(body_id.hir_id) {
|
|
hir::Node::Expr(expr) => {
|
|
if hir::is_range_literal(expr) {
|
|
let span = self.tcx.hir().span(body_id.hir_id);
|
|
if let Ok(snip) = self.tcx.sess.source_map().span_to_snippet(span) {
|
|
e.span_suggestion_verbose(
|
|
ident.span,
|
|
"you may want to move the range into the match block",
|
|
snip,
|
|
Applicability::MachineApplicable,
|
|
);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
_ => (),
|
|
},
|
|
_ => (),
|
|
},
|
|
_ => (),
|
|
}
|
|
false
|
|
}
|
|
|
|
fn emit_bad_pat_path(
|
|
&self,
|
|
mut e: DiagnosticBuilder<'_>,
|
|
pat_span: Span,
|
|
res: Res,
|
|
pat_res: Res,
|
|
pat_ty: Ty<'tcx>,
|
|
segments: &'b [hir::PathSegment<'b>],
|
|
parent_pat: Option<&Pat<'_>>,
|
|
) {
|
|
if let Some(span) = self.tcx.hir().res_span(pat_res) {
|
|
e.span_label(span, &format!("{} defined here", res.descr()));
|
|
if let [hir::PathSegment { ident, .. }] = &*segments {
|
|
e.span_label(
|
|
pat_span,
|
|
&format!(
|
|
"`{}` is interpreted as {} {}, not a new binding",
|
|
ident,
|
|
res.article(),
|
|
res.descr(),
|
|
),
|
|
);
|
|
match parent_pat {
|
|
Some(Pat { kind: hir::PatKind::Struct(..), .. }) => {
|
|
e.span_suggestion_verbose(
|
|
ident.span.shrink_to_hi(),
|
|
"bind the struct field to a different name instead",
|
|
format!(": other_{}", ident.as_str().to_lowercase()),
|
|
Applicability::HasPlaceholders,
|
|
);
|
|
}
|
|
_ => {
|
|
let (type_def_id, item_def_id) = match pat_ty.kind() {
|
|
Adt(def, _) => match res {
|
|
Res::Def(DefKind::Const, def_id) => (Some(def.did), Some(def_id)),
|
|
_ => (None, None),
|
|
},
|
|
_ => (None, None),
|
|
};
|
|
|
|
let ranges = &[
|
|
self.tcx.lang_items().range_struct(),
|
|
self.tcx.lang_items().range_from_struct(),
|
|
self.tcx.lang_items().range_to_struct(),
|
|
self.tcx.lang_items().range_full_struct(),
|
|
self.tcx.lang_items().range_inclusive_struct(),
|
|
self.tcx.lang_items().range_to_inclusive_struct(),
|
|
];
|
|
if type_def_id != None && ranges.contains(&type_def_id) {
|
|
if !self.maybe_suggest_range_literal(&mut e, item_def_id, *ident) {
|
|
let msg = "constants only support matching by type, \
|
|
if you meant to match against a range of values, \
|
|
consider using a range pattern like `min ..= max` in the match block";
|
|
e.note(msg);
|
|
}
|
|
} else {
|
|
let msg = "introduce a new binding instead";
|
|
let sugg = format!("other_{}", ident.as_str().to_lowercase());
|
|
e.span_suggestion(
|
|
ident.span,
|
|
msg,
|
|
sugg,
|
|
Applicability::HasPlaceholders,
|
|
);
|
|
}
|
|
}
|
|
};
|
|
}
|
|
}
|
|
e.emit();
|
|
}
|
|
|
|
fn check_pat_tuple_struct(
|
|
&self,
|
|
pat: &'tcx Pat<'tcx>,
|
|
qpath: &hir::QPath<'_>,
|
|
subpats: &'tcx [&'tcx Pat<'tcx>],
|
|
ddpos: Option<usize>,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let tcx = self.tcx;
|
|
let on_error = || {
|
|
let parent_pat = Some(pat);
|
|
for pat in subpats {
|
|
self.check_pat(&pat, tcx.ty_error(), def_bm, TopInfo { parent_pat, ..ti });
|
|
}
|
|
};
|
|
let report_unexpected_res = |res: Res| {
|
|
let sm = tcx.sess.source_map();
|
|
let path_str = sm
|
|
.span_to_snippet(sm.span_until_char(pat.span, '('))
|
|
.map_or_else(|_| String::new(), |s| format!(" `{}`", s.trim_end()));
|
|
let msg = format!(
|
|
"expected tuple struct or tuple variant, found {}{}",
|
|
res.descr(),
|
|
path_str
|
|
);
|
|
|
|
let mut err = struct_span_err!(tcx.sess, pat.span, E0164, "{}", msg);
|
|
match res {
|
|
Res::Def(DefKind::Fn | DefKind::AssocFn, _) => {
|
|
err.span_label(pat.span, "`fn` calls are not allowed in patterns");
|
|
err.help(
|
|
"for more information, visit \
|
|
https://doc.rust-lang.org/book/ch18-00-patterns.html",
|
|
);
|
|
}
|
|
_ => {
|
|
err.span_label(pat.span, "not a tuple variant or struct");
|
|
}
|
|
}
|
|
err.emit();
|
|
on_error();
|
|
};
|
|
|
|
// Resolve the path and check the definition for errors.
|
|
let (res, opt_ty, segments) = self.resolve_ty_and_res_ufcs(qpath, pat.hir_id, pat.span);
|
|
if res == Res::Err {
|
|
self.set_tainted_by_errors();
|
|
on_error();
|
|
return self.tcx.ty_error();
|
|
}
|
|
|
|
// Type-check the path.
|
|
let (pat_ty, res) =
|
|
self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id);
|
|
if !pat_ty.is_fn() {
|
|
report_unexpected_res(res);
|
|
return tcx.ty_error();
|
|
}
|
|
|
|
let variant = match res {
|
|
Res::Err => {
|
|
self.set_tainted_by_errors();
|
|
on_error();
|
|
return tcx.ty_error();
|
|
}
|
|
Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => {
|
|
report_unexpected_res(res);
|
|
return tcx.ty_error();
|
|
}
|
|
Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) => tcx.expect_variant_res(res),
|
|
_ => bug!("unexpected pattern resolution: {:?}", res),
|
|
};
|
|
|
|
// Replace constructor type with constructed type for tuple struct patterns.
|
|
let pat_ty = pat_ty.fn_sig(tcx).output();
|
|
let pat_ty = pat_ty.no_bound_vars().expect("expected fn type");
|
|
|
|
// Type-check the tuple struct pattern against the expected type.
|
|
let diag = self.demand_eqtype_pat_diag(pat.span, expected, pat_ty, ti);
|
|
let had_err = if let Some(mut err) = diag {
|
|
err.emit();
|
|
true
|
|
} else {
|
|
false
|
|
};
|
|
|
|
// Type-check subpatterns.
|
|
if subpats.len() == variant.fields.len()
|
|
|| subpats.len() < variant.fields.len() && ddpos.is_some()
|
|
{
|
|
let substs = match pat_ty.kind() {
|
|
ty::Adt(_, substs) => substs,
|
|
_ => bug!("unexpected pattern type {:?}", pat_ty),
|
|
};
|
|
for (i, subpat) in subpats.iter().enumerate_and_adjust(variant.fields.len(), ddpos) {
|
|
let field_ty = self.field_ty(subpat.span, &variant.fields[i], substs);
|
|
self.check_pat(&subpat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
|
|
|
|
self.tcx.check_stability(variant.fields[i].did, Some(pat.hir_id), subpat.span);
|
|
}
|
|
} else {
|
|
// Pattern has wrong number of fields.
|
|
self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err);
|
|
on_error();
|
|
return tcx.ty_error();
|
|
}
|
|
pat_ty
|
|
}
|
|
|
|
fn e0023(
|
|
&self,
|
|
pat_span: Span,
|
|
res: Res,
|
|
qpath: &hir::QPath<'_>,
|
|
subpats: &'tcx [&'tcx Pat<'tcx>],
|
|
fields: &'tcx [ty::FieldDef],
|
|
expected: Ty<'tcx>,
|
|
had_err: bool,
|
|
) {
|
|
let subpats_ending = pluralize!(subpats.len());
|
|
let fields_ending = pluralize!(fields.len());
|
|
let res_span = self.tcx.def_span(res.def_id());
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
pat_span,
|
|
E0023,
|
|
"this pattern has {} field{}, but the corresponding {} has {} field{}",
|
|
subpats.len(),
|
|
subpats_ending,
|
|
res.descr(),
|
|
fields.len(),
|
|
fields_ending,
|
|
);
|
|
err.span_label(
|
|
pat_span,
|
|
format!("expected {} field{}, found {}", fields.len(), fields_ending, subpats.len(),),
|
|
)
|
|
.span_label(res_span, format!("{} defined here", res.descr()));
|
|
|
|
// Identify the case `Some(x, y)` where the expected type is e.g. `Option<(T, U)>`.
|
|
// More generally, the expected type wants a tuple variant with one field of an
|
|
// N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern
|
|
// with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
|
|
let missing_parentheses = match (&expected.kind(), fields, had_err) {
|
|
// #67037: only do this if we could successfully type-check the expected type against
|
|
// the tuple struct pattern. Otherwise the substs could get out of range on e.g.,
|
|
// `let P() = U;` where `P != U` with `struct P<T>(T);`.
|
|
(ty::Adt(_, substs), [field], false) => {
|
|
let field_ty = self.field_ty(pat_span, field, substs);
|
|
match field_ty.kind() {
|
|
ty::Tuple(_) => field_ty.tuple_fields().count() == subpats.len(),
|
|
_ => false,
|
|
}
|
|
}
|
|
_ => false,
|
|
};
|
|
if missing_parentheses {
|
|
let (left, right) = match subpats {
|
|
// This is the zero case; we aim to get the "hi" part of the `QPath`'s
|
|
// span as the "lo" and then the "hi" part of the pattern's span as the "hi".
|
|
// This looks like:
|
|
//
|
|
// help: missing parentheses
|
|
// |
|
|
// L | let A(()) = A(());
|
|
// | ^ ^
|
|
[] => (qpath.span().shrink_to_hi(), pat_span),
|
|
// Easy case. Just take the "lo" of the first sub-pattern and the "hi" of the
|
|
// last sub-pattern. In the case of `A(x)` the first and last may coincide.
|
|
// This looks like:
|
|
//
|
|
// help: missing parentheses
|
|
// |
|
|
// L | let A((x, y)) = A((1, 2));
|
|
// | ^ ^
|
|
[first, ..] => (first.span.shrink_to_lo(), subpats.last().unwrap().span),
|
|
};
|
|
err.multipart_suggestion(
|
|
"missing parentheses",
|
|
vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())],
|
|
Applicability::MachineApplicable,
|
|
);
|
|
} else if fields.len() > subpats.len() && pat_span != DUMMY_SP {
|
|
let after_fields_span = pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi();
|
|
let all_fields_span = match subpats {
|
|
[] => after_fields_span,
|
|
[field] => field.span,
|
|
[first, .., last] => first.span.to(last.span),
|
|
};
|
|
|
|
// Check if all the fields in the pattern are wildcards.
|
|
let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild));
|
|
let first_tail_wildcard =
|
|
subpats.iter().enumerate().fold(None, |acc, (pos, pat)| match (acc, &pat.kind) {
|
|
(None, PatKind::Wild) => Some(pos),
|
|
(Some(_), PatKind::Wild) => acc,
|
|
_ => None,
|
|
});
|
|
let tail_span = match first_tail_wildcard {
|
|
None => after_fields_span,
|
|
Some(0) => subpats[0].span.to(after_fields_span),
|
|
Some(pos) => subpats[pos - 1].span.shrink_to_hi().to(after_fields_span),
|
|
};
|
|
|
|
// FIXME: heuristic-based suggestion to check current types for where to add `_`.
|
|
let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", ");
|
|
if !subpats.is_empty() {
|
|
wildcard_sugg = String::from(", ") + &wildcard_sugg;
|
|
}
|
|
|
|
err.span_suggestion_verbose(
|
|
after_fields_span,
|
|
"use `_` to explicitly ignore each field",
|
|
wildcard_sugg,
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
|
|
// Only suggest `..` if more than one field is missing
|
|
// or the pattern consists of all wildcards.
|
|
if fields.len() - subpats.len() > 1 || all_wildcards {
|
|
if subpats.is_empty() || all_wildcards {
|
|
err.span_suggestion_verbose(
|
|
all_fields_span,
|
|
"use `..` to ignore all fields",
|
|
String::from(".."),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
} else {
|
|
err.span_suggestion_verbose(
|
|
tail_span,
|
|
"use `..` to ignore the rest of the fields",
|
|
String::from(", .."),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
err.emit();
|
|
}
|
|
|
|
fn check_pat_tuple(
|
|
&self,
|
|
span: Span,
|
|
elements: &'tcx [&'tcx Pat<'tcx>],
|
|
ddpos: Option<usize>,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let tcx = self.tcx;
|
|
let mut expected_len = elements.len();
|
|
if ddpos.is_some() {
|
|
// Require known type only when `..` is present.
|
|
if let ty::Tuple(ref tys) = self.structurally_resolved_type(span, expected).kind() {
|
|
expected_len = tys.len();
|
|
}
|
|
}
|
|
let max_len = cmp::max(expected_len, elements.len());
|
|
|
|
let element_tys_iter = (0..max_len).map(|_| {
|
|
GenericArg::from(self.next_ty_var(
|
|
// FIXME: `MiscVariable` for now -- obtaining the span and name information
|
|
// from all tuple elements isn't trivial.
|
|
TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span },
|
|
))
|
|
});
|
|
let element_tys = tcx.mk_substs(element_tys_iter);
|
|
let pat_ty = tcx.mk_ty(ty::Tuple(element_tys));
|
|
if let Some(mut err) = self.demand_eqtype_pat_diag(span, expected, pat_ty, ti) {
|
|
err.emit();
|
|
// Walk subpatterns with an expected type of `err` in this case to silence
|
|
// further errors being emitted when using the bindings. #50333
|
|
let element_tys_iter = (0..max_len).map(|_| tcx.ty_error());
|
|
for (_, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) {
|
|
self.check_pat(elem, &tcx.ty_error(), def_bm, ti);
|
|
}
|
|
tcx.mk_tup(element_tys_iter)
|
|
} else {
|
|
for (i, elem) in elements.iter().enumerate_and_adjust(max_len, ddpos) {
|
|
self.check_pat(elem, &element_tys[i].expect_ty(), def_bm, ti);
|
|
}
|
|
pat_ty
|
|
}
|
|
}
|
|
|
|
fn check_struct_pat_fields(
|
|
&self,
|
|
adt_ty: Ty<'tcx>,
|
|
pat: &'tcx Pat<'tcx>,
|
|
variant: &'tcx ty::VariantDef,
|
|
fields: &'tcx [hir::PatField<'tcx>],
|
|
etc: bool,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> bool {
|
|
let tcx = self.tcx;
|
|
|
|
let (substs, adt) = match adt_ty.kind() {
|
|
ty::Adt(adt, substs) => (substs, adt),
|
|
_ => span_bug!(pat.span, "struct pattern is not an ADT"),
|
|
};
|
|
|
|
// Index the struct fields' types.
|
|
let field_map = variant
|
|
.fields
|
|
.iter()
|
|
.enumerate()
|
|
.map(|(i, field)| (field.ident.normalize_to_macros_2_0(), (i, field)))
|
|
.collect::<FxHashMap<_, _>>();
|
|
|
|
// Keep track of which fields have already appeared in the pattern.
|
|
let mut used_fields = FxHashMap::default();
|
|
let mut no_field_errors = true;
|
|
|
|
let mut inexistent_fields = vec![];
|
|
// Typecheck each field.
|
|
for field in fields {
|
|
let span = field.span;
|
|
let ident = tcx.adjust_ident(field.ident, variant.def_id);
|
|
let field_ty = match used_fields.entry(ident) {
|
|
Occupied(occupied) => {
|
|
self.error_field_already_bound(span, field.ident, *occupied.get());
|
|
no_field_errors = false;
|
|
tcx.ty_error()
|
|
}
|
|
Vacant(vacant) => {
|
|
vacant.insert(span);
|
|
field_map
|
|
.get(&ident)
|
|
.map(|(i, f)| {
|
|
self.write_field_index(field.hir_id, *i);
|
|
self.tcx.check_stability(f.did, Some(pat.hir_id), span);
|
|
self.field_ty(span, f, substs)
|
|
})
|
|
.unwrap_or_else(|| {
|
|
inexistent_fields.push(field.ident);
|
|
no_field_errors = false;
|
|
tcx.ty_error()
|
|
})
|
|
}
|
|
};
|
|
|
|
self.check_pat(&field.pat, field_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
|
|
}
|
|
|
|
let mut unmentioned_fields = variant
|
|
.fields
|
|
.iter()
|
|
.map(|field| (field, field.ident.normalize_to_macros_2_0()))
|
|
.filter(|(_, ident)| !used_fields.contains_key(&ident))
|
|
.collect::<Vec<_>>();
|
|
|
|
let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered()) {
|
|
Some(self.error_inexistent_fields(
|
|
adt.variant_descr(),
|
|
&inexistent_fields,
|
|
&mut unmentioned_fields,
|
|
variant,
|
|
))
|
|
} else {
|
|
None
|
|
};
|
|
|
|
// Require `..` if struct has non_exhaustive attribute.
|
|
if variant.is_field_list_non_exhaustive() && !adt.did.is_local() && !etc {
|
|
self.error_foreign_non_exhaustive_spat(pat, adt.variant_descr(), fields.is_empty());
|
|
}
|
|
|
|
let mut unmentioned_err = None;
|
|
// Report an error if an incorrect number of fields was specified.
|
|
if adt.is_union() {
|
|
if fields.len() != 1 {
|
|
tcx.sess
|
|
.struct_span_err(pat.span, "union patterns should have exactly one field")
|
|
.emit();
|
|
}
|
|
if etc {
|
|
tcx.sess.struct_span_err(pat.span, "`..` cannot be used in union patterns").emit();
|
|
}
|
|
} else if !etc && !unmentioned_fields.is_empty() {
|
|
let no_accessible_unmentioned_fields = !unmentioned_fields.iter().any(|(field, _)| {
|
|
field.vis.is_accessible_from(tcx.parent_module(pat.hir_id).to_def_id(), tcx)
|
|
});
|
|
|
|
if no_accessible_unmentioned_fields {
|
|
unmentioned_err = Some(self.error_no_accessible_fields(pat, &fields));
|
|
} else {
|
|
unmentioned_err =
|
|
Some(self.error_unmentioned_fields(pat, &unmentioned_fields, &fields));
|
|
}
|
|
}
|
|
match (inexistent_fields_err, unmentioned_err) {
|
|
(Some(mut i), Some(mut u)) => {
|
|
if let Some(mut e) = self.error_tuple_variant_as_struct_pat(pat, fields, variant) {
|
|
// We don't want to show the inexistent fields error when this was
|
|
// `Foo { a, b }` when it should have been `Foo(a, b)`.
|
|
i.delay_as_bug();
|
|
u.delay_as_bug();
|
|
e.emit();
|
|
} else {
|
|
i.emit();
|
|
u.emit();
|
|
}
|
|
}
|
|
(None, Some(mut u)) => {
|
|
if let Some(mut e) = self.error_tuple_variant_as_struct_pat(pat, fields, variant) {
|
|
u.delay_as_bug();
|
|
e.emit();
|
|
} else {
|
|
u.emit();
|
|
}
|
|
}
|
|
(Some(mut err), None) => {
|
|
err.emit();
|
|
}
|
|
(None, None) => {
|
|
if let Some(mut err) =
|
|
self.error_tuple_variant_index_shorthand(variant, pat, fields)
|
|
{
|
|
err.emit();
|
|
}
|
|
}
|
|
}
|
|
no_field_errors
|
|
}
|
|
|
|
fn error_tuple_variant_index_shorthand(
|
|
&self,
|
|
variant: &VariantDef,
|
|
pat: &'_ Pat<'_>,
|
|
fields: &[hir::PatField<'_>],
|
|
) -> Option<DiagnosticBuilder<'_>> {
|
|
// if this is a tuple struct, then all field names will be numbers
|
|
// so if any fields in a struct pattern use shorthand syntax, they will
|
|
// be invalid identifiers (for example, Foo { 0, 1 }).
|
|
if let (CtorKind::Fn, PatKind::Struct(qpath, field_patterns, ..)) =
|
|
(variant.ctor_kind, &pat.kind)
|
|
{
|
|
let has_shorthand_field_name = field_patterns.iter().any(|field| field.is_shorthand);
|
|
if has_shorthand_field_name {
|
|
let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
|
|
s.print_qpath(qpath, false)
|
|
});
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
pat.span,
|
|
E0769,
|
|
"tuple variant `{}` written as struct variant",
|
|
path
|
|
);
|
|
err.span_suggestion_verbose(
|
|
qpath.span().shrink_to_hi().to(pat.span.shrink_to_hi()),
|
|
"use the tuple variant pattern syntax instead",
|
|
format!("({})", self.get_suggested_tuple_struct_pattern(fields, variant)),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
return Some(err);
|
|
}
|
|
}
|
|
None
|
|
}
|
|
|
|
fn error_foreign_non_exhaustive_spat(&self, pat: &Pat<'_>, descr: &str, no_fields: bool) {
|
|
let sess = self.tcx.sess;
|
|
let sm = sess.source_map();
|
|
let sp_brace = sm.end_point(pat.span);
|
|
let sp_comma = sm.end_point(pat.span.with_hi(sp_brace.hi()));
|
|
let sugg = if no_fields || sp_brace != sp_comma { ".. }" } else { ", .. }" };
|
|
|
|
let mut err = struct_span_err!(
|
|
sess,
|
|
pat.span,
|
|
E0638,
|
|
"`..` required with {} marked as non-exhaustive",
|
|
descr
|
|
);
|
|
err.span_suggestion_verbose(
|
|
sp_comma,
|
|
"add `..` at the end of the field list to ignore all other fields",
|
|
sugg.to_string(),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
err.emit();
|
|
}
|
|
|
|
fn error_field_already_bound(&self, span: Span, ident: Ident, other_field: Span) {
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0025,
|
|
"field `{}` bound multiple times in the pattern",
|
|
ident
|
|
)
|
|
.span_label(span, format!("multiple uses of `{}` in pattern", ident))
|
|
.span_label(other_field, format!("first use of `{}`", ident))
|
|
.emit();
|
|
}
|
|
|
|
fn error_inexistent_fields(
|
|
&self,
|
|
kind_name: &str,
|
|
inexistent_fields: &[Ident],
|
|
unmentioned_fields: &mut Vec<(&ty::FieldDef, Ident)>,
|
|
variant: &ty::VariantDef,
|
|
) -> DiagnosticBuilder<'tcx> {
|
|
let tcx = self.tcx;
|
|
let (field_names, t, plural) = if inexistent_fields.len() == 1 {
|
|
(format!("a field named `{}`", inexistent_fields[0]), "this", "")
|
|
} else {
|
|
(
|
|
format!(
|
|
"fields named {}",
|
|
inexistent_fields
|
|
.iter()
|
|
.map(|ident| format!("`{}`", ident))
|
|
.collect::<Vec<String>>()
|
|
.join(", ")
|
|
),
|
|
"these",
|
|
"s",
|
|
)
|
|
};
|
|
let spans = inexistent_fields.iter().map(|ident| ident.span).collect::<Vec<_>>();
|
|
let mut err = struct_span_err!(
|
|
tcx.sess,
|
|
spans,
|
|
E0026,
|
|
"{} `{}` does not have {}",
|
|
kind_name,
|
|
tcx.def_path_str(variant.def_id),
|
|
field_names
|
|
);
|
|
if let Some(ident) = inexistent_fields.last() {
|
|
err.span_label(
|
|
ident.span,
|
|
format!(
|
|
"{} `{}` does not have {} field{}",
|
|
kind_name,
|
|
tcx.def_path_str(variant.def_id),
|
|
t,
|
|
plural
|
|
),
|
|
);
|
|
if plural == "" {
|
|
let input =
|
|
unmentioned_fields.iter().map(|(_, field)| field.name).collect::<Vec<_>>();
|
|
let suggested_name = find_best_match_for_name(&input, ident.name, None);
|
|
if let Some(suggested_name) = suggested_name {
|
|
err.span_suggestion(
|
|
ident.span,
|
|
"a field with a similar name exists",
|
|
suggested_name.to_string(),
|
|
Applicability::MaybeIncorrect,
|
|
);
|
|
|
|
// When we have a tuple struct used with struct we don't want to suggest using
|
|
// the (valid) struct syntax with numeric field names. Instead we want to
|
|
// suggest the expected syntax. We infer that this is the case by parsing the
|
|
// `Ident` into an unsized integer. The suggestion will be emitted elsewhere in
|
|
// `smart_resolve_context_dependent_help`.
|
|
if suggested_name.to_ident_string().parse::<usize>().is_err() {
|
|
// We don't want to throw `E0027` in case we have thrown `E0026` for them.
|
|
unmentioned_fields.retain(|&(_, x)| x.name != suggested_name);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if tcx.sess.teach(&err.get_code().unwrap()) {
|
|
err.note(
|
|
"This error indicates that a struct pattern attempted to \
|
|
extract a non-existent field from a struct. Struct fields \
|
|
are identified by the name used before the colon : so struct \
|
|
patterns should resemble the declaration of the struct type \
|
|
being matched.\n\n\
|
|
If you are using shorthand field patterns but want to refer \
|
|
to the struct field by a different name, you should rename \
|
|
it explicitly.",
|
|
);
|
|
}
|
|
err
|
|
}
|
|
|
|
fn error_tuple_variant_as_struct_pat(
|
|
&self,
|
|
pat: &Pat<'_>,
|
|
fields: &'tcx [hir::PatField<'tcx>],
|
|
variant: &ty::VariantDef,
|
|
) -> Option<DiagnosticBuilder<'tcx>> {
|
|
if let (CtorKind::Fn, PatKind::Struct(qpath, ..)) = (variant.ctor_kind, &pat.kind) {
|
|
let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
|
|
s.print_qpath(qpath, false)
|
|
});
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
pat.span,
|
|
E0769,
|
|
"tuple variant `{}` written as struct variant",
|
|
path
|
|
);
|
|
let (sugg, appl) = if fields.len() == variant.fields.len() {
|
|
(
|
|
self.get_suggested_tuple_struct_pattern(fields, variant),
|
|
Applicability::MachineApplicable,
|
|
)
|
|
} else {
|
|
(
|
|
variant.fields.iter().map(|_| "_").collect::<Vec<&str>>().join(", "),
|
|
Applicability::MaybeIncorrect,
|
|
)
|
|
};
|
|
err.span_suggestion_verbose(
|
|
qpath.span().shrink_to_hi().to(pat.span.shrink_to_hi()),
|
|
"use the tuple variant pattern syntax instead",
|
|
format!("({})", sugg),
|
|
appl,
|
|
);
|
|
return Some(err);
|
|
}
|
|
None
|
|
}
|
|
|
|
fn get_suggested_tuple_struct_pattern(
|
|
&self,
|
|
fields: &[hir::PatField<'_>],
|
|
variant: &VariantDef,
|
|
) -> String {
|
|
let variant_field_idents = variant.fields.iter().map(|f| f.ident).collect::<Vec<Ident>>();
|
|
fields
|
|
.iter()
|
|
.map(|field| {
|
|
match self.tcx.sess.source_map().span_to_snippet(field.pat.span) {
|
|
Ok(f) => {
|
|
// Field names are numbers, but numbers
|
|
// are not valid identifiers
|
|
if variant_field_idents.contains(&field.ident) {
|
|
String::from("_")
|
|
} else {
|
|
f
|
|
}
|
|
}
|
|
Err(_) => rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
|
|
s.print_pat(field.pat)
|
|
}),
|
|
}
|
|
})
|
|
.collect::<Vec<String>>()
|
|
.join(", ")
|
|
}
|
|
|
|
/// Returns a diagnostic reporting a struct pattern which is missing an `..` due to
|
|
/// inaccessible fields.
|
|
///
|
|
/// ```text
|
|
/// error: pattern requires `..` due to inaccessible fields
|
|
/// --> src/main.rs:10:9
|
|
/// |
|
|
/// LL | let foo::Foo {} = foo::Foo::default();
|
|
/// | ^^^^^^^^^^^
|
|
/// |
|
|
/// help: add a `..`
|
|
/// |
|
|
/// LL | let foo::Foo { .. } = foo::Foo::default();
|
|
/// | ^^^^^^
|
|
/// ```
|
|
fn error_no_accessible_fields(
|
|
&self,
|
|
pat: &Pat<'_>,
|
|
fields: &'tcx [hir::PatField<'tcx>],
|
|
) -> DiagnosticBuilder<'tcx> {
|
|
let mut err = self
|
|
.tcx
|
|
.sess
|
|
.struct_span_err(pat.span, "pattern requires `..` due to inaccessible fields");
|
|
|
|
if let Some(field) = fields.last() {
|
|
err.span_suggestion_verbose(
|
|
field.span.shrink_to_hi(),
|
|
"ignore the inaccessible and unused fields",
|
|
", ..".to_string(),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
} else {
|
|
let qpath_span = if let PatKind::Struct(qpath, ..) = &pat.kind {
|
|
qpath.span()
|
|
} else {
|
|
bug!("`error_no_accessible_fields` called on non-struct pattern");
|
|
};
|
|
|
|
// Shrink the span to exclude the `foo:Foo` in `foo::Foo { }`.
|
|
let span = pat.span.with_lo(qpath_span.shrink_to_hi().hi());
|
|
err.span_suggestion_verbose(
|
|
span,
|
|
"ignore the inaccessible and unused fields",
|
|
" { .. }".to_string(),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|
|
err
|
|
}
|
|
|
|
/// Returns a diagnostic reporting a struct pattern which does not mention some fields.
|
|
///
|
|
/// ```text
|
|
/// error[E0027]: pattern does not mention field `bar`
|
|
/// --> src/main.rs:15:9
|
|
/// |
|
|
/// LL | let foo::Foo {} = foo::Foo::new();
|
|
/// | ^^^^^^^^^^^ missing field `bar`
|
|
/// ```
|
|
fn error_unmentioned_fields(
|
|
&self,
|
|
pat: &Pat<'_>,
|
|
unmentioned_fields: &[(&ty::FieldDef, Ident)],
|
|
fields: &'tcx [hir::PatField<'tcx>],
|
|
) -> DiagnosticBuilder<'tcx> {
|
|
let field_names = if unmentioned_fields.len() == 1 {
|
|
format!("field `{}`", unmentioned_fields[0].1)
|
|
} else {
|
|
let fields = unmentioned_fields
|
|
.iter()
|
|
.map(|(_, name)| format!("`{}`", name))
|
|
.collect::<Vec<String>>()
|
|
.join(", ");
|
|
format!("fields {}", fields)
|
|
};
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
pat.span,
|
|
E0027,
|
|
"pattern does not mention {}",
|
|
field_names
|
|
);
|
|
err.span_label(pat.span, format!("missing {}", field_names));
|
|
let len = unmentioned_fields.len();
|
|
let (prefix, postfix, sp) = match fields {
|
|
[] => match &pat.kind {
|
|
PatKind::Struct(path, [], false) => {
|
|
(" { ", " }", path.span().shrink_to_hi().until(pat.span.shrink_to_hi()))
|
|
}
|
|
_ => return err,
|
|
},
|
|
[.., field] => {
|
|
// Account for last field having a trailing comma or parse recovery at the tail of
|
|
// the pattern to avoid invalid suggestion (#78511).
|
|
let tail = field.span.shrink_to_hi().with_hi(pat.span.hi());
|
|
match &pat.kind {
|
|
PatKind::Struct(..) => (", ", " }", tail),
|
|
_ => return err,
|
|
}
|
|
}
|
|
};
|
|
err.span_suggestion(
|
|
sp,
|
|
&format!(
|
|
"include the missing field{} in the pattern",
|
|
if len == 1 { "" } else { "s" },
|
|
),
|
|
format!(
|
|
"{}{}{}",
|
|
prefix,
|
|
unmentioned_fields
|
|
.iter()
|
|
.map(|(_, name)| name.to_string())
|
|
.collect::<Vec<_>>()
|
|
.join(", "),
|
|
postfix,
|
|
),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
err.span_suggestion(
|
|
sp,
|
|
&format!(
|
|
"if you don't care about {} missing field{}, you can explicitly ignore {}",
|
|
if len == 1 { "this" } else { "these" },
|
|
if len == 1 { "" } else { "s" },
|
|
if len == 1 { "it" } else { "them" },
|
|
),
|
|
format!("{}..{}", prefix, postfix),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
err
|
|
}
|
|
|
|
fn check_pat_box(
|
|
&self,
|
|
span: Span,
|
|
inner: &'tcx Pat<'tcx>,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let tcx = self.tcx;
|
|
let (box_ty, inner_ty) = if self.check_dereferenceable(span, expected, &inner) {
|
|
// Here, `demand::subtype` is good enough, but I don't
|
|
// think any errors can be introduced by using `demand::eqtype`.
|
|
let inner_ty = self.next_ty_var(TypeVariableOrigin {
|
|
kind: TypeVariableOriginKind::TypeInference,
|
|
span: inner.span,
|
|
});
|
|
let box_ty = tcx.mk_box(inner_ty);
|
|
self.demand_eqtype_pat(span, expected, box_ty, ti);
|
|
(box_ty, inner_ty)
|
|
} else {
|
|
let err = tcx.ty_error();
|
|
(err, err)
|
|
};
|
|
self.check_pat(&inner, inner_ty, def_bm, ti);
|
|
box_ty
|
|
}
|
|
|
|
fn check_pat_ref(
|
|
&self,
|
|
pat: &'tcx Pat<'tcx>,
|
|
inner: &'tcx Pat<'tcx>,
|
|
mutbl: hir::Mutability,
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let tcx = self.tcx;
|
|
let expected = self.shallow_resolve(expected);
|
|
let (rptr_ty, inner_ty) = if self.check_dereferenceable(pat.span, expected, &inner) {
|
|
// `demand::subtype` would be good enough, but using `eqtype` turns
|
|
// out to be equally general. See (note_1) for details.
|
|
|
|
// Take region, inner-type from expected type if we can,
|
|
// to avoid creating needless variables. This also helps with
|
|
// the bad interactions of the given hack detailed in (note_1).
|
|
debug!("check_pat_ref: expected={:?}", expected);
|
|
match *expected.kind() {
|
|
ty::Ref(_, r_ty, r_mutbl) if r_mutbl == mutbl => (expected, r_ty),
|
|
_ => {
|
|
let inner_ty = self.next_ty_var(TypeVariableOrigin {
|
|
kind: TypeVariableOriginKind::TypeInference,
|
|
span: inner.span,
|
|
});
|
|
let rptr_ty = self.new_ref_ty(pat.span, mutbl, inner_ty);
|
|
debug!("check_pat_ref: demanding {:?} = {:?}", expected, rptr_ty);
|
|
let err = self.demand_eqtype_pat_diag(pat.span, expected, rptr_ty, ti);
|
|
|
|
// Look for a case like `fn foo(&foo: u32)` and suggest
|
|
// `fn foo(foo: &u32)`
|
|
if let Some(mut err) = err {
|
|
self.borrow_pat_suggestion(&mut err, &pat, &inner, &expected);
|
|
err.emit();
|
|
}
|
|
(rptr_ty, inner_ty)
|
|
}
|
|
}
|
|
} else {
|
|
let err = tcx.ty_error();
|
|
(err, err)
|
|
};
|
|
self.check_pat(&inner, inner_ty, def_bm, TopInfo { parent_pat: Some(&pat), ..ti });
|
|
rptr_ty
|
|
}
|
|
|
|
/// Create a reference type with a fresh region variable.
|
|
fn new_ref_ty(&self, span: Span, mutbl: hir::Mutability, ty: Ty<'tcx>) -> Ty<'tcx> {
|
|
let region = self.next_region_var(infer::PatternRegion(span));
|
|
let mt = ty::TypeAndMut { ty, mutbl };
|
|
self.tcx.mk_ref(region, mt)
|
|
}
|
|
|
|
/// Type check a slice pattern.
|
|
///
|
|
/// Syntactically, these look like `[pat_0, ..., pat_n]`.
|
|
/// Semantically, we are type checking a pattern with structure:
|
|
/// ```
|
|
/// [before_0, ..., before_n, (slice, after_0, ... after_n)?]
|
|
/// ```
|
|
/// The type of `slice`, if it is present, depends on the `expected` type.
|
|
/// If `slice` is missing, then so is `after_i`.
|
|
/// If `slice` is present, it can still represent 0 elements.
|
|
fn check_pat_slice(
|
|
&self,
|
|
span: Span,
|
|
before: &'tcx [&'tcx Pat<'tcx>],
|
|
slice: Option<&'tcx Pat<'tcx>>,
|
|
after: &'tcx [&'tcx Pat<'tcx>],
|
|
expected: Ty<'tcx>,
|
|
def_bm: BindingMode,
|
|
ti: TopInfo<'tcx>,
|
|
) -> Ty<'tcx> {
|
|
let expected = self.structurally_resolved_type(span, expected);
|
|
let (element_ty, opt_slice_ty, inferred) = match *expected.kind() {
|
|
// An array, so we might have something like `let [a, b, c] = [0, 1, 2];`.
|
|
ty::Array(element_ty, len) => {
|
|
let min = before.len() as u64 + after.len() as u64;
|
|
let (opt_slice_ty, expected) =
|
|
self.check_array_pat_len(span, element_ty, expected, slice, len, min);
|
|
// `opt_slice_ty.is_none()` => `slice.is_none()`.
|
|
// Note, though, that opt_slice_ty could be `Some(error_ty)`.
|
|
assert!(opt_slice_ty.is_some() || slice.is_none());
|
|
(element_ty, opt_slice_ty, expected)
|
|
}
|
|
ty::Slice(element_ty) => (element_ty, Some(expected), expected),
|
|
// The expected type must be an array or slice, but was neither, so error.
|
|
_ => {
|
|
if !expected.references_error() {
|
|
self.error_expected_array_or_slice(span, expected);
|
|
}
|
|
let err = self.tcx.ty_error();
|
|
(err, Some(err), err)
|
|
}
|
|
};
|
|
|
|
// Type check all the patterns before `slice`.
|
|
for elt in before {
|
|
self.check_pat(&elt, element_ty, def_bm, ti);
|
|
}
|
|
// Type check the `slice`, if present, against its expected type.
|
|
if let Some(slice) = slice {
|
|
self.check_pat(&slice, opt_slice_ty.unwrap(), def_bm, ti);
|
|
}
|
|
// Type check the elements after `slice`, if present.
|
|
for elt in after {
|
|
self.check_pat(&elt, element_ty, def_bm, ti);
|
|
}
|
|
inferred
|
|
}
|
|
|
|
/// Type check the length of an array pattern.
|
|
///
|
|
/// Returns both the type of the variable length pattern (or `None`), and the potentially
|
|
/// inferred array type. We only return `None` for the slice type if `slice.is_none()`.
|
|
fn check_array_pat_len(
|
|
&self,
|
|
span: Span,
|
|
element_ty: Ty<'tcx>,
|
|
arr_ty: Ty<'tcx>,
|
|
slice: Option<&'tcx Pat<'tcx>>,
|
|
len: &ty::Const<'tcx>,
|
|
min_len: u64,
|
|
) -> (Option<Ty<'tcx>>, Ty<'tcx>) {
|
|
if let Some(len) = len.try_eval_usize(self.tcx, self.param_env) {
|
|
// Now we know the length...
|
|
if slice.is_none() {
|
|
// ...and since there is no variable-length pattern,
|
|
// we require an exact match between the number of elements
|
|
// in the array pattern and as provided by the matched type.
|
|
if min_len == len {
|
|
return (None, arr_ty);
|
|
}
|
|
|
|
self.error_scrutinee_inconsistent_length(span, min_len, len);
|
|
} else if let Some(pat_len) = len.checked_sub(min_len) {
|
|
// The variable-length pattern was there,
|
|
// so it has an array type with the remaining elements left as its size...
|
|
return (Some(self.tcx.mk_array(element_ty, pat_len)), arr_ty);
|
|
} else {
|
|
// ...however, in this case, there were no remaining elements.
|
|
// That is, the slice pattern requires more than the array type offers.
|
|
self.error_scrutinee_with_rest_inconsistent_length(span, min_len, len);
|
|
}
|
|
} else if slice.is_none() {
|
|
// We have a pattern with a fixed length,
|
|
// which we can use to infer the length of the array.
|
|
let updated_arr_ty = self.tcx.mk_array(element_ty, min_len);
|
|
self.demand_eqtype(span, updated_arr_ty, arr_ty);
|
|
return (None, updated_arr_ty);
|
|
} else {
|
|
// We have a variable-length pattern and don't know the array length.
|
|
// This happens if we have e.g.,
|
|
// `let [a, b, ..] = arr` where `arr: [T; N]` where `const N: usize`.
|
|
self.error_scrutinee_unfixed_length(span);
|
|
}
|
|
|
|
// If we get here, we must have emitted an error.
|
|
(Some(self.tcx.ty_error()), arr_ty)
|
|
}
|
|
|
|
fn error_scrutinee_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0527,
|
|
"pattern requires {} element{} but array has {}",
|
|
min_len,
|
|
pluralize!(min_len),
|
|
size,
|
|
)
|
|
.span_label(span, format!("expected {} element{}", size, pluralize!(size)))
|
|
.emit();
|
|
}
|
|
|
|
fn error_scrutinee_with_rest_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0528,
|
|
"pattern requires at least {} element{} but array has {}",
|
|
min_len,
|
|
pluralize!(min_len),
|
|
size,
|
|
)
|
|
.span_label(
|
|
span,
|
|
format!("pattern cannot match array of {} element{}", size, pluralize!(size),),
|
|
)
|
|
.emit();
|
|
}
|
|
|
|
fn error_scrutinee_unfixed_length(&self, span: Span) {
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0730,
|
|
"cannot pattern-match on an array without a fixed length",
|
|
)
|
|
.emit();
|
|
}
|
|
|
|
fn error_expected_array_or_slice(&self, span: Span, expected_ty: Ty<'tcx>) {
|
|
let mut err = struct_span_err!(
|
|
self.tcx.sess,
|
|
span,
|
|
E0529,
|
|
"expected an array or slice, found `{}`",
|
|
expected_ty
|
|
);
|
|
if let ty::Ref(_, ty, _) = expected_ty.kind() {
|
|
if let ty::Array(..) | ty::Slice(..) = ty.kind() {
|
|
err.help("the semantics of slice patterns changed recently; see issue #62254");
|
|
}
|
|
}
|
|
err.span_label(span, format!("pattern cannot match with input type `{}`", expected_ty));
|
|
err.emit();
|
|
}
|
|
}
|