bjoernager/rust
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Handle let-else initializer edge case errors

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This commit is contained in:
Cameron Steffen 2021-07-30 17:12:11 -05:00
parent 2f4e86b9ef
commit 29bc94ff0d
3 changed files with 101 additions and 15 deletions
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46
compiler/rustc_parse/src/parser/stmt.rs
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@ -298,6 +298,8 @@ impl<'a> Parser<'a> {
Some(init) => {
if self.eat_keyword(kw::Else) {
let els = self.parse_block()?;
self.check_let_else_init_bool_expr(&init);
self.check_let_else_init_trailing_brace(&init);
LocalKind::InitElse(init, els)
} else {
LocalKind::Init(init)
@ -308,6 +310,50 @@ impl<'a> Parser<'a> {
Ok(P(ast::Local { ty, pat, kind, id: DUMMY_NODE_ID, span: lo.to(hi), attrs, tokens: None }))
}
fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
if let ast::ExprKind::Binary(op, ..) = init.kind {
if op.node.lazy() {
let suggs = vec![
(init.span.shrink_to_lo(), "(".to_string()),
(init.span.shrink_to_hi(), ")".to_string()),
];
self.struct_span_err(
init.span,
&format!(
"a `{}` expression cannot be directly assigned in `let...else`",
op.node.to_string()
),
)
.multipart_suggestion(
"wrap the expression in parenthesis",
suggs,
Applicability::MachineApplicable,
)
.emit();
}
}
}
fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
if let Some(trailing) = classify::expr_trailing_brace(init) {
let err_span = trailing.span.with_lo(trailing.span.hi() - BytePos(1));
let suggs = vec![
(trailing.span.shrink_to_lo(), "(".to_string()),
(trailing.span.shrink_to_hi(), ")".to_string()),
];
self.struct_span_err(
err_span,
"right curly brace `}` before `else` in a `let...else` statement not allowed",
)
.multipart_suggestion(
"try wrapping the expression in parenthesis",
suggs,
Applicability::MachineApplicable,
)
.emit();
}
}
/// Parses the RHS of a local variable declaration (e.g., `= 14;`).
fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
let eq_consumed = match self.token.kind {