bjoernager/rust
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Account for if (let pat = expr) {}

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Partially address #82827.
This commit is contained in:
Esteban Küber 2021-03-06 18:29:41 -08:00
parent 1c77a1fa3c
commit e62a543344
8 changed files with 216 additions and 231 deletions
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31
compiler/rustc_lint/src/unused.rs
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@ -602,7 +602,7 @@ trait UnusedDelimLint {
use rustc_ast::ExprKind::*;
let (value, ctx, followed_by_block, left_pos, right_pos) = match e.kind {
// Do not lint `unused_braces` in `if let` expressions.
If(ref cond, ref block, ..)
If(ref cond, ref block, _)
if !matches!(cond.kind, Let(_, _)) || Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX =>
{
let left = e.span.lo() + rustc_span::BytePos(2);
@ -816,8 +816,33 @@ impl UnusedParens {
impl EarlyLintPass for UnusedParens {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
if let ExprKind::Let(ref pat, ..) | ExprKind::ForLoop(ref pat, ..) = e.kind {
self.check_unused_parens_pat(cx, pat, false, false);
match e.kind {
ExprKind::Let(ref pat, _) | ExprKind::ForLoop(ref pat, ..) => {
self.check_unused_parens_pat(cx, pat, false, false);
}
// We ignore parens in cases like `if (((let Some(0) = Some(1))))` because we already
// handle a hard error for them during AST lowering in `lower_expr_mut`, but we still
// want to complain about things like `if let 42 = (42)`.
ExprKind::If(ref cond, ref block, ref else_)
if matches!(cond.peel_parens().kind, ExprKind::Let(..)) =>
{
self.check_unused_delims_expr(
cx,
cond.peel_parens(),
UnusedDelimsCtx::LetScrutineeExpr,
true,
None,
None,
);
for stmt in &block.stmts {
<Self as UnusedDelimLint>::check_stmt(self, cx, stmt);
}
if let Some(e) = else_ {
<Self as UnusedDelimLint>::check_expr(self, cx, e);
}
return;
}
_ => {}
}
<Self as UnusedDelimLint>::check_expr(self, cx, e)