rustc_parse: improve the error diagnostic for "missing let in let chain"
Signed-off-by: Usman Akinyemi <usmanakinyemi202@gmail.com>
This commit is contained in:
Usman Akinyemi
parent
b3cda168c8
commit
9ca8ed38eb
5 changed files with 73 additions and 40 deletions
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@ -2760,9 +2760,13 @@ impl<'a> Parser<'a> {
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let (mut cond, _) =
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self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, attrs)?;
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CondChecker::new(self, let_chains_policy).visit_expr(&mut cond);
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Ok(cond)
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let mut checker = CondChecker::new(self, let_chains_policy);
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checker.visit_expr(&mut cond);
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Ok(if let Some(guar) = checker.found_incorrect_let_chain {
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self.mk_expr_err(cond.span, guar)
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} else {
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cond
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})
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}
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/// Parses a `let $pat = $expr` pseudo-expression.
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@ -3484,13 +3488,19 @@ impl<'a> Parser<'a> {
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let if_span = self.prev_token.span;
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let mut cond = self.parse_match_guard_condition()?;
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CondChecker::new(self, LetChainsPolicy::AlwaysAllowed).visit_expr(&mut cond);
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let mut checker = CondChecker::new(self, LetChainsPolicy::AlwaysAllowed);
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checker.visit_expr(&mut cond);
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if has_let_expr(&cond) {
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let span = if_span.to(cond.span);
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self.psess.gated_spans.gate(sym::if_let_guard, span);
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}
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Ok(Some(cond))
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Ok(Some(if let Some(guar) = checker.found_incorrect_let_chain {
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self.mk_expr_err(cond.span, guar)
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} else {
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cond
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}))
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}
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fn parse_match_arm_pat_and_guard(&mut self) -> PResult<'a, (Pat, Option<Box<Expr>>)> {
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@ -3511,13 +3521,23 @@ impl<'a> Parser<'a> {
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let ast::PatKind::Paren(subpat) = pat.kind else { unreachable!() };
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let ast::PatKind::Guard(_, mut cond) = subpat.kind else { unreachable!() };
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self.psess.gated_spans.ungate_last(sym::guard_patterns, cond.span);
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CondChecker::new(self, LetChainsPolicy::AlwaysAllowed).visit_expr(&mut cond);
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let mut checker = CondChecker::new(self, LetChainsPolicy::AlwaysAllowed);
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checker.visit_expr(&mut cond);
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let right = self.prev_token.span;
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self.dcx().emit_err(errors::ParenthesesInMatchPat {
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span: vec![left, right],
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sugg: errors::ParenthesesInMatchPatSugg { left, right },
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});
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Ok((self.mk_pat(span, ast::PatKind::Wild), Some(cond)))
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Ok((
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self.mk_pat(span, ast::PatKind::Wild),
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(if let Some(guar) = checker.found_incorrect_let_chain {
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Some(self.mk_expr_err(cond.span, guar))
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} else {
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Some(cond)
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}),
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))
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} else {
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Ok((pat, self.parse_match_arm_guard()?))
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}
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@ -4208,6 +4228,7 @@ struct CondChecker<'a> {
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forbid_let_reason: Option<ForbiddenLetReason>,
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missing_let: Option<errors::MaybeMissingLet>,
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comparison: Option<errors::MaybeComparison>,
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found_incorrect_let_chain: Option<ErrorGuaranteed>,
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}
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impl<'a> CondChecker<'a> {
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@ -4218,6 +4239,7 @@ impl<'a> CondChecker<'a> {
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missing_let: None,
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comparison: None,
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let_chains_policy,
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found_incorrect_let_chain: None,
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depth: 0,
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}
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}
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@ -4236,12 +4258,19 @@ impl MutVisitor for CondChecker<'_> {
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NotSupportedOr(or_span) => {
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self.parser.dcx().emit_err(errors::OrInLetChain { span: or_span })
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}
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_ => self.parser.dcx().emit_err(errors::ExpectedExpressionFoundLet {
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span,
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reason,
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missing_let: self.missing_let,
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comparison: self.comparison,
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}),
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_ => {
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let guar =
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self.parser.dcx().emit_err(errors::ExpectedExpressionFoundLet {
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span,
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reason,
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missing_let: self.missing_let,
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comparison: self.comparison,
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});
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if let Some(_) = self.missing_let {
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self.found_incorrect_let_chain = Some(guar);
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}
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guar
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}
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};
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*recovered = Recovered::Yes(error);
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} else if self.depth > 1 {
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@ -1,8 +1,6 @@
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fn a() {
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if let x = 1 && i = 2 {}
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//~^ ERROR cannot find value `i` in this scope
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//~| ERROR mismatched types
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//~| ERROR expected expression, found `let` statement
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//~^ ERROR expected expression, found `let` statement
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}
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fn b() {
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@ -15,13 +15,7 @@ LL | if let x = 1 && i == 2 {}
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| +
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error[E0425]: cannot find value `i` in this scope
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--> $DIR/bad-if-let-suggestion.rs:2:21
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LL | if let x = 1 && i = 2 {}
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| ^ not found in this scope
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error[E0425]: cannot find value `i` in this scope
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--> $DIR/bad-if-let-suggestion.rs:9:9
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--> $DIR/bad-if-let-suggestion.rs:7:9
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LL | fn a() {
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| ------ similarly named function `a` defined here
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@ -36,7 +30,7 @@ LL + if (a + j) = i {}
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error[E0425]: cannot find value `j` in this scope
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--> $DIR/bad-if-let-suggestion.rs:9:13
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--> $DIR/bad-if-let-suggestion.rs:7:13
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LL | fn a() {
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| ------ similarly named function `a` defined here
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@ -51,7 +45,7 @@ LL + if (i + a) = i {}
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error[E0425]: cannot find value `i` in this scope
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--> $DIR/bad-if-let-suggestion.rs:9:18
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--> $DIR/bad-if-let-suggestion.rs:7:18
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LL | fn a() {
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| ------ similarly named function `a` defined here
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@ -66,7 +60,7 @@ LL + if (i + j) = a {}
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error[E0425]: cannot find value `x` in this scope
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--> $DIR/bad-if-let-suggestion.rs:16:8
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--> $DIR/bad-if-let-suggestion.rs:14:8
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LL | fn a() {
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| ------ similarly named function `a` defined here
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@ -80,18 +74,6 @@ LL - if x[0] = 1 {}
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LL + if a[0] = 1 {}
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error[E0308]: mismatched types
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--> $DIR/bad-if-let-suggestion.rs:2:8
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LL | if let x = 1 && i = 2 {}
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| ^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
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help: you might have meant to compare for equality
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LL | if let x = 1 && i == 2 {}
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| +
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error: aborting due to 5 previous errors
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error: aborting due to 7 previous errors
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Some errors have detailed explanations: E0308, E0425.
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For more information about an error, try `rustc --explain E0308`.
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For more information about this error, try `rustc --explain E0425`.
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6
tests/ui/missing/missing-let.rs
Normal file
6
tests/ui/missing/missing-let.rs
Normal file
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@ -0,0 +1,6 @@
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fn main() {
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let x = Some(42);
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if let Some(_) = x
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&& Some(x) = x //~^ ERROR expected expression, found `let` statement
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{}
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}
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18
tests/ui/missing/missing-let.stderr
Normal file
18
tests/ui/missing/missing-let.stderr
Normal file
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@ -0,0 +1,18 @@
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error: expected expression, found `let` statement
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--> $DIR/missing-let.rs:3:8
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LL | if let Some(_) = x
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| ^^^^^^^^^^^^^^^
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= note: only supported directly in conditions of `if` and `while` expressions
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help: you might have meant to continue the let-chain
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LL | && let Some(x) = x
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| +++
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help: you might have meant to compare for equality
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LL | && Some(x) == x
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| +
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error: aborting due to 1 previous error
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