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Narrow span of temp holding the value of a Block expression to the block's tail (if present).

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This commit is contained in:
Felix S. Klock II 2018-11-08 12:39:54 +01:00
parent ece4f472c9
commit 3011ecdeac
1 changed files with 24 additions and 1 deletions
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25
src/librustc_mir/build/expr/stmt.rs
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@ -201,7 +201,30 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
}
_ => {
let expr_ty = expr.ty;
let temp = this.temp(expr.ty.clone(), expr_span);
// Issue #54382: When creating temp for the value of
// expression like:
//
// `{ side_effects(); { let l = stuff(); the_value } }`
//
// it is usually better to focus on `the_value` rather
// than the entirety of block(s) surrounding it.
let mut temp_span = expr_span;
if let ExprKind::Block { body } = expr.kind {
if let Some(tail_expr) = &body.expr {
let mut expr = tail_expr;
while let rustc::hir::ExprKind::Block(subblock, _label) = &expr.node {
if let Some(subtail_expr) = &subblock.expr {
expr = subtail_expr
} else {
break;
}
}
temp_span = expr.span;
}
}
let temp = this.temp(expr.ty.clone(), temp_span);
unpack!(block = this.into(&temp, block, expr));
// Attribute drops of the statement's temps to the