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Change the for-loop desugar so the break does not affect type inference. Fixes #42618

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This commit is contained in:
John Kåre Alsaker 2017-06-13 18:36:01 +02:00
parent 3f8b93693d
commit dbb655a1e3
2 changed files with 31 additions and 12 deletions
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6
src/libcore/iter/mod.rs
View File

@ -191,10 +191,12 @@
//! {
//! let result = match IntoIterator::into_iter(values) {
//! mut iter => loop {
//! let x = match iter.next() {
//! Some(val) => val,
//! let next;
//! match iter.next() {
//! Some(val) => next = val,
//! None => break,
//! };
//! let x = next;
//! let () = { println!("{}", x); };
//! },
//! };

37
src/librustc/hir/lowering.rs
View File

@ -2170,11 +2170,13 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
// let result = match ::std::iter::IntoIterator::into_iter(<head>) {
// mut iter => {
// [opt_ident]: loop {
// let <pat> = match ::std::iter::Iterator::next(&mut iter) {
// ::std::option::Option::Some(val) => val,
// let next;
// match ::std::iter::Iterator::next(&mut iter) {
// ::std::option::Option::Some(val) => next = val,
// ::std::option::Option::None => break
// };
// SemiExpr(<body>);
// let <pat> = next;
// StmtExpr(<body>);
// }
// }
// };
@ -2186,13 +2188,18 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
let iter = self.str_to_ident("iter");
// `::std::option::Option::Some(val) => val`
let next_ident = self.str_to_ident("next");
let next_pat = self.pat_ident(e.span, next_ident);
// `::std::option::Option::Some(val) => next = val`
let pat_arm = {
let val_ident = self.str_to_ident("val");
let val_pat = self.pat_ident(e.span, val_ident);
let val_expr = P(self.expr_ident(e.span, val_ident, val_pat.id));
let next_expr = P(self.expr_ident(e.span, next_ident, next_pat.id));
let assign = P(self.expr(e.span, hir::ExprAssign(next_expr, val_expr), ThinVec::new()));
let some_pat = self.pat_some(e.span, val_pat);
self.arm(hir_vec![some_pat], val_expr)
self.arm(hir_vec![some_pat], assign)
};
// `::std::option::Option::None => break`
@ -2222,10 +2229,20 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
hir::MatchSource::ForLoopDesugar),
ThinVec::new()))
};
let match_stmt = respan(e.span, hir::StmtExpr(match_expr, self.next_id()));
let next_expr = P(self.expr_ident(e.span, next_ident, next_pat.id));
// `let next`
let next_let = self.stmt_let_pat(e.span,
None,
next_pat,
hir::LocalSource::ForLoopDesugar);
// `let <pat> = next`
let pat = self.lower_pat(pat);
let pat_let = self.stmt_let_pat(e.span,
match_expr,
Some(next_expr),
pat,
hir::LocalSource::ForLoopDesugar);
@ -2234,7 +2251,7 @@ fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
let body_expr = P(self.expr_block(body_block, ThinVec::new()));
let body_stmt = respan(e.span, hir::StmtExpr(body_expr, self.next_id()));
let loop_block = P(self.block_all(e.span, hir_vec![pat_let, body_stmt], None));
let loop_block = P(self.block_all(e.span, hir_vec![next_let, match_stmt, pat_let, body_stmt], None));
// `[opt_ident]: loop { ... }`
let loop_expr = hir::ExprLoop(loop_block, self.lower_opt_sp_ident(opt_ident),
@ -2601,14 +2618,14 @@ fn expr(&mut self, span: Span, node: hir::Expr_, attrs: ThinVec<Attribute>) -> h
fn stmt_let_pat(&mut self,
sp: Span,
ex: P<hir::Expr>,
ex: Option<P<hir::Expr>>,
pat: P<hir::Pat>,
source: hir::LocalSource)
-> hir::Stmt {
let local = P(hir::Local {
pat: pat,
ty: None,
init: Some(ex),
init: ex,
id: self.next_id(),
span: sp,
attrs: ThinVec::new(),
@ -2626,7 +2643,7 @@ fn stmt_let(&mut self, sp: Span, mutbl: bool, ident: Name, ex: P<hir::Expr>)
self.pat_ident(sp, ident)
};
let pat_id = pat.id;
(self.stmt_let_pat(sp, ex, pat, hir::LocalSource::Normal), pat_id)
(self.stmt_let_pat(sp, Some(ex), pat, hir::LocalSource::Normal), pat_id)
}
fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {