Auto merge of #52242 - ashtneoi:suggest-ref-mut, r=pnkfelix
NLL: Suggest `ref mut` and `&mut self` Fixes #51244. Supersedes #51249, I think. Under the old lexical lifetimes, the compiler provided helpful suggestions about adding `mut` when you tried to mutate a variable bound as `&self` or (explicit) `ref`. NLL doesn't have those suggestions yet. This pull request adds them. I didn't bother making the help text exactly the same as without NLL, but I can if that's important. (Originally this was supposed to be part of #51612, but I got bogged down trying to fit everything in one PR.)
This commit is contained in:
commit
fe29a4cda5
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@ -39,6 +39,7 @@ use rustc::middle::free_region::RegionRelations;
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use rustc::ty::{self, Ty, TyCtxt};
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use rustc::ty::query::Providers;
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use rustc_mir::util::borrowck_errors::{BorrowckErrors, Origin};
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use rustc_mir::util::suggest_ref_mut;
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use rustc::util::nodemap::FxHashSet;
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use std::cell::RefCell;
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@ -1206,15 +1207,15 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
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self.note_immutable_local(db, error_node_id, node_id)
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}
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Some(ImmutabilityBlame::LocalDeref(node_id)) => {
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let let_span = self.tcx.hir.span(node_id);
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match self.local_binding_mode(node_id) {
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ty::BindByReference(..) => {
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let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
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if let Ok(snippet) = snippet {
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db.span_label(
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let let_span = self.tcx.hir.span(node_id);
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let suggestion = suggest_ref_mut(self.tcx, let_span);
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if let Some((let_span, replace_str)) = suggestion {
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db.span_suggestion(
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let_span,
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format!("consider changing this to `{}`",
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snippet.replace("ref ", "ref mut "))
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"use a mutable reference instead",
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replace_str,
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);
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}
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}
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@ -44,6 +44,7 @@ use dataflow::{EverInitializedPlaces, MovingOutStatements};
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use dataflow::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
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use util::borrowck_errors::{BorrowckErrors, Origin};
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use util::collect_writes::FindAssignments;
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use util::suggest_ref_mut;
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use self::borrow_set::{BorrowData, BorrowSet};
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use self::flows::Flows;
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@ -1837,17 +1838,41 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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Place::Projection(box Projection {
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base: Place::Local(local),
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elem: ProjectionElem::Deref,
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}) if self.mir.local_decls[*local].is_nonref_binding() =>
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{
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let (err_help_span, suggested_code) =
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find_place_to_suggest_ampmut(self.tcx, self.mir, *local);
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err.span_suggestion(
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err_help_span,
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"consider changing this to be a mutable reference",
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suggested_code,
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);
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}) if self.mir.local_decls[*local].is_user_variable.is_some() => {
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let local_decl = &self.mir.local_decls[*local];
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let suggestion = match local_decl.is_user_variable.as_ref().unwrap() {
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ClearCrossCrate::Set(mir::BindingForm::ImplicitSelf) => {
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Some(suggest_ampmut_self(local_decl))
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},
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ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
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binding_mode: ty::BindingMode::BindByValue(_),
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opt_ty_info,
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..
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})) => Some(suggest_ampmut(
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self.tcx,
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self.mir,
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*local,
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local_decl,
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*opt_ty_info,
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)),
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ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
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binding_mode: ty::BindingMode::BindByReference(_),
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..
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})) => suggest_ref_mut(self.tcx, local_decl.source_info.span),
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ClearCrossCrate::Clear => bug!("saw cleared local state"),
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};
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if let Some((err_help_span, suggested_code)) = suggestion {
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err.span_suggestion(
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err_help_span,
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"consider changing this to be a mutable reference",
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suggested_code,
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);
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}
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if let Some(name) = local_decl.name {
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err.span_label(
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span,
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@ -1874,13 +1899,16 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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err.emit();
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return true;
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// Returns the span to highlight and the associated text to
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// present when suggesting that the user use an `&mut`.
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//
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fn suggest_ampmut_self<'cx, 'gcx, 'tcx>(
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local_decl: &mir::LocalDecl<'tcx>,
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) -> (Span, String) {
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(local_decl.source_info.span, "&mut self".to_string())
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}
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// When we want to suggest a user change a local variable to be a `&mut`, there
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// are three potential "obvious" things to highlight:
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//
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// let ident [: Type] [= RightHandSideExresssion];
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// let ident [: Type] [= RightHandSideExpression];
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// ^^^^^ ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^
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// (1.) (2.) (3.)
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//
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@ -1889,48 +1917,44 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
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// for example, if the RHS is present and the Type is not, then the type is going to
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// be inferred *from* the RHS, which means we should highlight that (and suggest
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// that they borrow the RHS mutably).
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fn find_place_to_suggest_ampmut<'cx, 'gcx, 'tcx>(
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//
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// This implementation attempts to emulate AST-borrowck prioritization
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// by trying (3.), then (2.) and finally falling back on (1.).
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fn suggest_ampmut<'cx, 'gcx, 'tcx>(
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tcx: TyCtxt<'cx, 'gcx, 'tcx>,
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mir: &Mir<'tcx>,
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local: Local,
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local_decl: &mir::LocalDecl<'tcx>,
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opt_ty_info: Option<Span>,
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) -> (Span, String) {
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// This implementation attempts to emulate AST-borrowck prioritization
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// by trying (3.), then (2.) and finally falling back on (1.).
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let locations = mir.find_assignments(local);
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if locations.len() > 0 {
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let assignment_rhs_span = mir.source_info(locations[0]).span;
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let snippet = tcx.sess.codemap().span_to_snippet(assignment_rhs_span);
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if let Ok(src) = snippet {
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// pnkfelix inherited code; believes intention is
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// highlighted text will always be `&<expr>` and
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// thus can transform to `&mut` by slicing off
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// first ASCII character and prepending "&mut ".
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if src.starts_with('&') {
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let borrowed_expr = src[1..].to_string();
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return (assignment_rhs_span, format!("&mut {}", borrowed_expr));
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return (
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assignment_rhs_span,
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format!("&mut {}", borrowed_expr),
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);
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}
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}
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}
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let local_decl = &mir.local_decls[local];
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let highlight_span = match local_decl.is_user_variable {
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let highlight_span = match opt_ty_info {
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// if this is a variable binding with an explicit type,
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// try to highlight that for the suggestion.
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Some(ClearCrossCrate::Set(mir::BindingForm::Var(mir::VarBindingForm {
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opt_ty_info: Some(ty_span),
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..
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}))) => ty_span,
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Some(ClearCrossCrate::Clear) => bug!("saw cleared local state"),
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Some(ty_span) => ty_span,
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// otherwise, just highlight the span associated with
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// the (MIR) LocalDecl.
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_ => local_decl.source_info.span,
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None => local_decl.source_info.span,
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};
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let ty_mut = local_decl.ty.builtin_deref(true).unwrap();
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assert_eq!(ty_mut.mutbl, hir::MutImmutable);
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return (highlight_span, format!("&mut {}", ty_mut.ty));
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(highlight_span, format!("&mut {}", ty_mut.ty))
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}
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}
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@ -33,6 +33,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
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#![feature(never_type)]
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#![feature(specialization)]
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#![feature(try_trait)]
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#![feature(unicode_internals)]
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#![recursion_limit="256"]
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@ -56,6 +57,7 @@ extern crate rustc_target;
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extern crate log_settings;
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extern crate rustc_apfloat;
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extern crate byteorder;
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extern crate core;
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mod diagnostics;
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@ -8,6 +8,10 @@
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use core::unicode::property::Pattern_White_Space;
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use rustc::ty;
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use syntax_pos::Span;
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pub mod borrowck_errors;
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pub mod elaborate_drops;
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pub mod def_use;
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@ -23,3 +27,19 @@ pub use self::alignment::is_disaligned;
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pub use self::pretty::{dump_enabled, dump_mir, write_mir_pretty, PassWhere};
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pub use self::graphviz::{write_mir_graphviz};
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pub use self::graphviz::write_node_label as write_graphviz_node_label;
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/// If possible, suggest replacing `ref` with `ref mut`.
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pub fn suggest_ref_mut<'cx, 'gcx, 'tcx>(
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tcx: ty::TyCtxt<'cx, 'gcx, 'tcx>,
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pattern_span: Span,
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) -> Option<(Span, String)> {
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let hi_src = tcx.sess.codemap().span_to_snippet(pattern_span).unwrap();
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if hi_src.starts_with("ref")
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&& hi_src["ref".len()..].starts_with(Pattern_White_Space)
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{
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let replacement = format!("ref mut{}", &hi_src["ref".len()..]);
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Some((pattern_span, replacement))
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} else {
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None
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}
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}
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|
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@ -2,7 +2,7 @@ error[E0596]: cannot borrow immutable item `*self.s` as mutable
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--> $DIR/issue-38147-1.rs:27:9
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|
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LL | fn f(&self) {
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| ----- help: consider changing this to be a mutable reference: `&mut Foo<'_>`
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| ----- help: consider changing this to be a mutable reference: `&mut self`
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LL | self.s.push('x'); //~ ERROR cannot borrow data mutably
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| ^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
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|
|
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@ -10,7 +10,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
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--> $DIR/issue-39544.rs:26:17
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|
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LL | fn foo<'z>(&'z self) {
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| -------- help: consider changing this to be a mutable reference: `&mut Z`
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| -------- help: consider changing this to be a mutable reference: `&mut self`
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LL | let _ = &mut self.x; //~ ERROR cannot borrow
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| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
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|
@ -18,7 +18,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
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--> $DIR/issue-39544.rs:30:17
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|
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LL | fn foo1(&self, other: &Z) {
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| ----- help: consider changing this to be a mutable reference: `&mut Z`
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| ----- help: consider changing this to be a mutable reference: `&mut self`
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LL | let _ = &mut self.x; //~ ERROR cannot borrow
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| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
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|
@ -35,7 +35,7 @@ error[E0596]: cannot borrow immutable item `self.x` as mutable
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--> $DIR/issue-39544.rs:35:17
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|
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LL | fn foo2<'a>(&'a self, other: &Z) {
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| -------- help: consider changing this to be a mutable reference: `&mut Z`
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| -------- help: consider changing this to be a mutable reference: `&mut self`
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LL | let _ = &mut self.x; //~ ERROR cannot borrow
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| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
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|
|
|
@ -0,0 +1,17 @@
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
|
||||
// file at the top-level directory of this distribution and at
|
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// http://rust-lang.org/COPYRIGHT.
|
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//
|
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
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// option. This file may not be copied, modified, or distributed
|
||||
// except according to those terms.
|
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|
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#![feature(nll)]
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fn main() {
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let ref my_ref @ _ = 0;
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*my_ref = 0;
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//~^ ERROR cannot assign to `*my_ref` which is behind a `&` reference [E0594]
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}
|
|
@ -0,0 +1,11 @@
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error[E0594]: cannot assign to `*my_ref` which is behind a `&` reference
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--> $DIR/issue-51244.rs:15:5
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|
|
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LL | let ref my_ref @ _ = 0;
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| -------------- help: consider changing this to be a mutable reference: `ref mut my_ref @ _`
|
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LL | *my_ref = 0;
|
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| ^^^^^^^^^^^ `my_ref` is a `&` reference, so the data it refers to cannot be written
|
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|
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error: aborting due to previous error
|
||||
|
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For more information about this error, try `rustc --explain E0594`.
|
|
@ -2,19 +2,19 @@ error[E0594]: cannot assign to `*x` which is behind a `&` reference
|
|||
--> $DIR/enum.rs:19:5
|
||||
|
|
||||
LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*x` which is behind a `&` reference
|
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--> $DIR/enum.rs:23:9
|
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|
|
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LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*x` which is behind a `&` reference
|
||||
--> $DIR/enum.rs:29:9
|
||||
|
|
||||
LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error: aborting due to 3 previous errors
|
||||
|
||||
|
|
|
@ -1,24 +1,18 @@
|
|||
error[E0594]: cannot assign to immutable borrowed content `*x`
|
||||
--> $DIR/enum.rs:19:5
|
||||
|
|
||||
LL | let Wrap(x) = &Wrap(3);
|
||||
| - consider changing this to `x`
|
||||
LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
error[E0594]: cannot assign to immutable borrowed content `*x`
|
||||
--> $DIR/enum.rs:23:9
|
||||
|
|
||||
LL | if let Some(x) = &Some(3) {
|
||||
| - consider changing this to `x`
|
||||
LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
error[E0594]: cannot assign to immutable borrowed content `*x`
|
||||
--> $DIR/enum.rs:29:9
|
||||
|
|
||||
LL | while let Some(x) = &Some(3) {
|
||||
| - consider changing this to `x`
|
||||
LL | *x += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
|
|
|
@ -2,19 +2,19 @@ error[E0594]: cannot assign to `*n` which is behind a `&` reference
|
|||
--> $DIR/explicit-mut.rs:17:13
|
||||
|
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*n` which is behind a `&` reference
|
||||
--> $DIR/explicit-mut.rs:25:13
|
||||
|
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*n` which is behind a `&` reference
|
||||
--> $DIR/explicit-mut.rs:33:13
|
||||
|
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot assign
|
||||
| ^^^^^^^ `n` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error: aborting due to 3 previous errors
|
||||
|
||||
|
|
|
@ -1,24 +1,18 @@
|
|||
error[E0594]: cannot assign to immutable borrowed content `*n`
|
||||
--> $DIR/explicit-mut.rs:17:13
|
||||
|
|
||||
LL | Some(n) => {
|
||||
| - consider changing this to `n`
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
error[E0594]: cannot assign to immutable borrowed content `*n`
|
||||
--> $DIR/explicit-mut.rs:25:13
|
||||
|
|
||||
LL | Some(n) => {
|
||||
| - consider changing this to `n`
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
error[E0594]: cannot assign to immutable borrowed content `*n`
|
||||
--> $DIR/explicit-mut.rs:33:13
|
||||
|
|
||||
LL | Some(n) => {
|
||||
| - consider changing this to `n`
|
||||
LL | *n += 1; //~ ERROR cannot assign to immutable
|
||||
| ^^^^^^^ cannot borrow as mutable
|
||||
|
||||
|
|
|
@ -0,0 +1,11 @@
|
|||
error[E0594]: cannot assign to `*my_ref` which is behind a `&` reference
|
||||
--> $DIR/issue-51244.rs:13:5
|
||||
|
|
||||
LL | let ref my_ref @ _ = 0;
|
||||
| -------------- help: consider changing this to be a mutable reference: `ref mut my_ref @ _`
|
||||
LL | *my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
|
||||
| ^^^^^^^^^^^ `my_ref` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
For more information about this error, try `rustc --explain E0594`.
|
|
@ -0,0 +1,14 @@
|
|||
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
|
||||
// file at the top-level directory of this distribution and at
|
||||
// http://rust-lang.org/COPYRIGHT.
|
||||
//
|
||||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
||||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
||||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
||||
// option. This file may not be copied, modified, or distributed
|
||||
// except according to those terms.
|
||||
|
||||
fn main() {
|
||||
let ref my_ref @ _ = 0;
|
||||
*my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
|
||||
}
|
|
@ -0,0 +1,11 @@
|
|||
error[E0594]: cannot assign to immutable borrowed content `*my_ref`
|
||||
--> $DIR/issue-51244.rs:13:5
|
||||
|
|
||||
LL | let ref my_ref @ _ = 0;
|
||||
| -------------- help: use a mutable reference instead: `ref mut my_ref @ _`
|
||||
LL | *my_ref = 0; //~ ERROR cannot assign to immutable borrowed content `*my_ref` [E0594]
|
||||
| ^^^^^^^^^^^ cannot borrow as mutable
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
For more information about this error, try `rustc --explain E0594`.
|
|
@ -0,0 +1,42 @@
|
|||
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
|
||||
// file at the top-level directory of this distribution and at
|
||||
// http://rust-lang.org/COPYRIGHT.
|
||||
//
|
||||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
||||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
||||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
||||
// option. This file may not be copied, modified, or distributed
|
||||
// except according to those terms.
|
||||
|
||||
#![feature(nll)]
|
||||
|
||||
struct X(usize);
|
||||
|
||||
impl X {
|
||||
fn zap(&self) {
|
||||
//~^ HELP
|
||||
//~| SUGGESTION &mut self
|
||||
self.0 = 32;
|
||||
//~^ ERROR
|
||||
}
|
||||
}
|
||||
|
||||
fn main() {
|
||||
let ref foo = 16;
|
||||
//~^ HELP
|
||||
//~| SUGGESTION ref mut foo
|
||||
*foo = 32;
|
||||
//~^ ERROR
|
||||
if let Some(ref bar) = Some(16) {
|
||||
//~^ HELP
|
||||
//~| SUGGESTION ref mut bar
|
||||
*bar = 32;
|
||||
//~^ ERROR
|
||||
}
|
||||
match 16 {
|
||||
ref quo => { *quo = 32; },
|
||||
//~^ ERROR
|
||||
//~| HELP
|
||||
//~| SUGGESTION ref mut quo
|
||||
}
|
||||
}
|
|
@ -0,0 +1,38 @@
|
|||
error[E0594]: cannot assign to `self.0` which is behind a `&` reference
|
||||
--> $DIR/suggest-ref-mut.rs:19:9
|
||||
|
|
||||
LL | fn zap(&self) {
|
||||
| ----- help: consider changing this to be a mutable reference: `&mut self`
|
||||
...
|
||||
LL | self.0 = 32;
|
||||
| ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*foo` which is behind a `&` reference
|
||||
--> $DIR/suggest-ref-mut.rs:28:5
|
||||
|
|
||||
LL | let ref foo = 16;
|
||||
| ------- help: consider changing this to be a mutable reference: `ref mut foo`
|
||||
...
|
||||
LL | *foo = 32;
|
||||
| ^^^^^^^^^ `foo` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*bar` which is behind a `&` reference
|
||||
--> $DIR/suggest-ref-mut.rs:33:9
|
||||
|
|
||||
LL | if let Some(ref bar) = Some(16) {
|
||||
| ------- help: consider changing this to be a mutable reference: `ref mut bar`
|
||||
...
|
||||
LL | *bar = 32;
|
||||
| ^^^^^^^^^ `bar` is a `&` reference, so the data it refers to cannot be written
|
||||
|
||||
error[E0594]: cannot assign to `*quo` which is behind a `&` reference
|
||||
--> $DIR/suggest-ref-mut.rs:37:22
|
||||
|
|
||||
LL | ref quo => { *quo = 32; },
|
||||
| ------- ^^^^^^^^^ `quo` is a `&` reference, so the data it refers to cannot be written
|
||||
| |
|
||||
| help: consider changing this to be a mutable reference: `ref mut quo`
|
||||
|
||||
error: aborting due to 4 previous errors
|
||||
|
||||
For more information about this error, try `rustc --explain E0594`.
|
Loading…
Reference in New Issue