269 lines
10 KiB
Rust
269 lines
10 KiB
Rust
//! This module contains functions for retrieve the original AST from lowered
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//! `hir`.
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#![deny(clippy::missing_docs_in_private_items)]
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use crate::{is_expn_of, match_def_path, paths};
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use if_chain::if_chain;
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use rustc_ast::ast;
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use rustc_hir as hir;
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use rustc_hir::{BorrowKind, Expr, ExprKind, StmtKind, UnOp};
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use rustc_lint::LateContext;
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use rustc_span::source_map::Span;
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/// Converts a hir binary operator to the corresponding `ast` type.
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#[must_use]
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pub fn binop(op: hir::BinOpKind) -> ast::BinOpKind {
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match op {
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hir::BinOpKind::Eq => ast::BinOpKind::Eq,
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hir::BinOpKind::Ge => ast::BinOpKind::Ge,
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hir::BinOpKind::Gt => ast::BinOpKind::Gt,
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hir::BinOpKind::Le => ast::BinOpKind::Le,
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hir::BinOpKind::Lt => ast::BinOpKind::Lt,
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hir::BinOpKind::Ne => ast::BinOpKind::Ne,
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hir::BinOpKind::Or => ast::BinOpKind::Or,
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hir::BinOpKind::Add => ast::BinOpKind::Add,
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hir::BinOpKind::And => ast::BinOpKind::And,
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hir::BinOpKind::BitAnd => ast::BinOpKind::BitAnd,
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hir::BinOpKind::BitOr => ast::BinOpKind::BitOr,
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hir::BinOpKind::BitXor => ast::BinOpKind::BitXor,
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hir::BinOpKind::Div => ast::BinOpKind::Div,
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hir::BinOpKind::Mul => ast::BinOpKind::Mul,
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hir::BinOpKind::Rem => ast::BinOpKind::Rem,
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hir::BinOpKind::Shl => ast::BinOpKind::Shl,
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hir::BinOpKind::Shr => ast::BinOpKind::Shr,
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hir::BinOpKind::Sub => ast::BinOpKind::Sub,
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}
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}
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/// Represent a range akin to `ast::ExprKind::Range`.
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#[derive(Debug, Copy, Clone)]
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pub struct Range<'a> {
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/// The lower bound of the range, or `None` for ranges such as `..X`.
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pub start: Option<&'a hir::Expr<'a>>,
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/// The upper bound of the range, or `None` for ranges such as `X..`.
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pub end: Option<&'a hir::Expr<'a>>,
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/// Whether the interval is open or closed.
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pub limits: ast::RangeLimits,
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}
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/// Higher a `hir` range to something similar to `ast::ExprKind::Range`.
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pub fn range<'a>(expr: &'a hir::Expr<'_>) -> Option<Range<'a>> {
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/// Finds the field named `name` in the field. Always return `Some` for
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/// convenience.
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fn get_field<'c>(name: &str, fields: &'c [hir::ExprField<'_>]) -> Option<&'c hir::Expr<'c>> {
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let expr = &fields.iter().find(|field| field.ident.name.as_str() == name)?.expr;
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Some(expr)
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}
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match expr.kind {
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hir::ExprKind::Call(ref path, ref args)
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if matches!(
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path.kind,
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hir::ExprKind::Path(hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, _))
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) =>
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{
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Some(Range {
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start: Some(&args[0]),
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end: Some(&args[1]),
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limits: ast::RangeLimits::Closed,
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})
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},
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hir::ExprKind::Struct(ref path, ref fields, None) => match path {
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hir::QPath::LangItem(hir::LangItem::RangeFull, _) => Some(Range {
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start: None,
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end: None,
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limits: ast::RangeLimits::HalfOpen,
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}),
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hir::QPath::LangItem(hir::LangItem::RangeFrom, _) => Some(Range {
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start: Some(get_field("start", fields)?),
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end: None,
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limits: ast::RangeLimits::HalfOpen,
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}),
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hir::QPath::LangItem(hir::LangItem::Range, _) => Some(Range {
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start: Some(get_field("start", fields)?),
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::HalfOpen,
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}),
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hir::QPath::LangItem(hir::LangItem::RangeToInclusive, _) => Some(Range {
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start: None,
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::Closed,
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}),
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hir::QPath::LangItem(hir::LangItem::RangeTo, _) => Some(Range {
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start: None,
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end: Some(get_field("end", fields)?),
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limits: ast::RangeLimits::HalfOpen,
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}),
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_ => None,
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},
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_ => None,
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}
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}
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/// Checks if a `let` statement is from a `for` loop desugaring.
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pub fn is_from_for_desugar(local: &hir::Local<'_>) -> bool {
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// This will detect plain for-loops without an actual variable binding:
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//
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// ```
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// for x in some_vec {
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// // do stuff
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// }
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// ```
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if_chain! {
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if let Some(ref expr) = local.init;
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if let hir::ExprKind::Match(_, _, hir::MatchSource::ForLoopDesugar) = expr.kind;
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then {
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return true;
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}
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}
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// This detects a variable binding in for loop to avoid `let_unit_value`
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// lint (see issue #1964).
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//
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// ```
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// for _ in vec![()] {
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// // anything
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// }
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// ```
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if let hir::LocalSource::ForLoopDesugar = local.source {
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return true;
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}
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false
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}
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/// Recover the essential nodes of a desugared for loop as well as the entire span:
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/// `for pat in arg { body }` becomes `(pat, arg, body)`. Return `(pat, arg, body, span)`.
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pub fn for_loop<'tcx>(
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expr: &'tcx hir::Expr<'tcx>,
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) -> Option<(&hir::Pat<'_>, &'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>, Span)> {
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if_chain! {
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if let hir::ExprKind::Match(ref iterexpr, ref arms, hir::MatchSource::ForLoopDesugar) = expr.kind;
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if let hir::ExprKind::Call(_, ref iterargs) = iterexpr.kind;
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if iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none();
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if let hir::ExprKind::Loop(ref block, ..) = arms[0].body.kind;
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if block.expr.is_none();
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if let [ _, _, ref let_stmt, ref body ] = *block.stmts;
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if let hir::StmtKind::Local(ref local) = let_stmt.kind;
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if let hir::StmtKind::Expr(ref expr) = body.kind;
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then {
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return Some((&*local.pat, &iterargs[0], expr, arms[0].span));
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}
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}
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None
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}
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/// Recover the essential nodes of a desugared while loop:
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/// `while cond { body }` becomes `(cond, body)`.
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pub fn while_loop<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>)> {
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if_chain! {
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if let hir::ExprKind::Loop(hir::Block { expr: Some(expr), .. }, _, hir::LoopSource::While, _) = &expr.kind;
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if let hir::ExprKind::Match(cond, arms, hir::MatchSource::WhileDesugar) = &expr.kind;
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if let hir::ExprKind::DropTemps(cond) = &cond.kind;
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if let [hir::Arm { body, .. }, ..] = &arms[..];
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then {
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return Some((cond, body));
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}
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}
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None
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}
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/// Represent the pre-expansion arguments of a `vec!` invocation.
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pub enum VecArgs<'a> {
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/// `vec![elem; len]`
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Repeat(&'a hir::Expr<'a>, &'a hir::Expr<'a>),
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/// `vec![a, b, c]`
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Vec(&'a [hir::Expr<'a>]),
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}
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/// Returns the arguments of the `vec!` macro if this expression was expanded
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/// from `vec!`.
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pub fn vec_macro<'e>(cx: &LateContext<'_>, expr: &'e hir::Expr<'_>) -> Option<VecArgs<'e>> {
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if_chain! {
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if let hir::ExprKind::Call(ref fun, ref args) = expr.kind;
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if let hir::ExprKind::Path(ref qpath) = fun.kind;
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if is_expn_of(fun.span, "vec").is_some();
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if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
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then {
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return if match_def_path(cx, fun_def_id, &paths::VEC_FROM_ELEM) && args.len() == 2 {
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// `vec![elem; size]` case
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Some(VecArgs::Repeat(&args[0], &args[1]))
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}
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else if match_def_path(cx, fun_def_id, &paths::SLICE_INTO_VEC) && args.len() == 1 {
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// `vec![a, b, c]` case
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if_chain! {
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if let hir::ExprKind::Box(ref boxed) = args[0].kind;
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if let hir::ExprKind::Array(ref args) = boxed.kind;
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then {
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return Some(VecArgs::Vec(&*args));
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}
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}
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None
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}
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else if match_def_path(cx, fun_def_id, &paths::VEC_NEW) && args.is_empty() {
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Some(VecArgs::Vec(&[]))
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}
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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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None
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}
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/// Extract args from an assert-like macro.
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/// Currently working with:
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/// - `assert!`, `assert_eq!` and `assert_ne!`
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/// - `debug_assert!`, `debug_assert_eq!` and `debug_assert_ne!`
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/// For example:
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/// `assert!(expr)` will return Some([expr])
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/// `debug_assert_eq!(a, b)` will return Some([a, b])
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pub fn extract_assert_macro_args<'tcx>(e: &'tcx Expr<'tcx>) -> Option<Vec<&'tcx Expr<'tcx>>> {
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/// Try to match the AST for a pattern that contains a match, for example when two args are
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/// compared
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fn ast_matchblock(matchblock_expr: &'tcx Expr<'tcx>) -> Option<Vec<&Expr<'_>>> {
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if_chain! {
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if let ExprKind::Match(ref headerexpr, _, _) = &matchblock_expr.kind;
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if let ExprKind::Tup([lhs, rhs]) = &headerexpr.kind;
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if let ExprKind::AddrOf(BorrowKind::Ref, _, lhs) = lhs.kind;
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if let ExprKind::AddrOf(BorrowKind::Ref, _, rhs) = rhs.kind;
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then {
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return Some(vec![lhs, rhs]);
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}
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}
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None
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}
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if let ExprKind::Block(ref block, _) = e.kind {
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if block.stmts.len() == 1 {
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if let StmtKind::Semi(ref matchexpr) = block.stmts.get(0)?.kind {
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// macros with unique arg: `{debug_}assert!` (e.g., `debug_assert!(some_condition)`)
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if_chain! {
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if let ExprKind::If(ref clause, _, _) = matchexpr.kind;
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if let ExprKind::Unary(UnOp::Not, condition) = clause.kind;
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then {
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return Some(vec![condition]);
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}
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}
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// debug macros with two args: `debug_assert_{ne, eq}` (e.g., `assert_ne!(a, b)`)
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if_chain! {
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if let ExprKind::Block(ref matchblock,_) = matchexpr.kind;
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if let Some(ref matchblock_expr) = matchblock.expr;
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then {
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return ast_matchblock(matchblock_expr);
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}
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}
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}
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} else if let Some(matchblock_expr) = block.expr {
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// macros with two args: `assert_{ne, eq}` (e.g., `assert_ne!(a, b)`)
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return ast_matchblock(&matchblock_expr);
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}
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}
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None
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}
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