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Rollup merge of #60676 - davidtwco:issue-60674, r=cramertj

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Fix async desugaring providing wrong input to procedural macros.

Fixes #60674.

This PR fixes a minor oversight introduced by #60535 where unused `mut` binding modes were removed from the arguments to an `async fn` (as they were added to the statement that we insert into the closure body). However, this meant that the input to procedural macros was incorrect. This removes that and instead fixes the `unused_mut` error that it avoided.

r? @cramertj
cc @taiki-e
This commit is contained in:
Mazdak Farrokhzad 2019-05-09 23:56:18 +02:00 • committed by GitHub
commit 45b09453db
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6 changed files with 76 additions and 43 deletions
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27
src/libsyntax/parse/parser.rs
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@ -50,7 +50,10 @@ use crate::symbol::{Symbol, keywords};
use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
use rustc_target::spec::abi::{self, Abi};
use syntax_pos::{Span, MultiSpan, BytePos, FileName};
use syntax_pos::{
Span, MultiSpan, BytePos, FileName,
hygiene::CompilerDesugaringKind,
};
use log::{debug, trace};
use std::borrow::Cow;
@ -8772,6 +8775,10 @@ impl<'a> Parser<'a> {
/// The arguments of the function are replaced in HIR lowering with the arguments created by
/// this function and the statements created here are inserted at the top of the closure body.
fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
// FIXME(davidtwco): This function should really live in the HIR lowering but because
// the types constructed here need to be used in parts of resolve so that the correct
// locals are considered upvars, it is currently easier for it to live here in the parser,
// where it can be constructed once.
if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
for (index, input) in decl.inputs.iter_mut().enumerate() {
let id = ast::DUMMY_NODE_ID;
@ -8786,6 +8793,15 @@ impl<'a> Parser<'a> {
// statement.
let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
// Simple patterns like this don't have a generated argument, but they are
// moved into the closure with a statement, so any `mut` bindings on the
// argument will be unused. This binding mode can't be removed, because
// this would affect the input to procedural macros, but they can have
// their span marked as being the result of a compiler desugaring so
// that they aren't linted against.
input.pat.span = self.sess.source_map().mark_span_with_reason(
CompilerDesugaringKind::Async, span, None);
(binding_mode, ident, true)
}
_ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
@ -8855,15 +8871,6 @@ impl<'a> Parser<'a> {
})
};
// Remove mutability from arguments. If this is not a simple pattern,
// those arguments are replaced by `__argN`, so there is no need to do this.
if let PatKind::Ident(BindingMode::ByValue(mutability @ Mutability::Mutable), ..) =
&mut input.pat.node
{
assert!(is_simple_pattern);
*mutability = Mutability::Immutable;
}
let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
}