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Emit a single error on if expr with expectation and no else clause

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This commit is contained in:
Esteban Küber 2019-08-31 18:34:50 -07:00
parent fba38ac27e
commit cab607edcf
5 changed files with 38 additions and 108 deletions
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41
src/librustc_typeck/check/_match.rs
View file

@ -112,23 +112,36 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
self.diverges.set(pats_diverge);
let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
all_arms_diverge &= self.diverges.get();
let span = expr.span;
if source_if {
let arm_ty = if source_if {
let then_expr = &arms[0].body;
match (i, if_no_else) {
(0, _) => coercion.coerce(self, &self.misc(span), &arm.body, arm_ty),
(_, true) => self.if_fallback_coercion(span, then_expr, &mut coercion),
(0, _) => {
let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
all_arms_diverge &= self.diverges.get();
coercion.coerce(self, &self.misc(expr.span), &arm.body, arm_ty);
arm_ty
}
(_, true) => {
if self.if_fallback_coercion(expr.span, then_expr, &mut coercion) {
tcx.types.err
} else {
let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
all_arms_diverge &= self.diverges.get();
arm_ty
}
}
(_, _) => {
let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
all_arms_diverge &= self.diverges.get();
let then_ty = prior_arm_ty.unwrap();
let cause = self.if_cause(span, then_expr, &arm.body, then_ty, arm_ty);
let cause = self.if_cause(expr.span, then_expr, &arm.body, then_ty, arm_ty);
coercion.coerce(self, &cause, &arm.body, arm_ty);
arm_ty
}
}
} else {
let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
all_arms_diverge &= self.diverges.get();
let arm_span = if let hir::ExprKind::Block(blk, _) = &arm.body.node {
// Point at the block expr instead of the entire block
blk.expr.as_ref().map(|e| e.span).unwrap_or(arm.body.span)
@ -139,7 +152,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// The reason for the first arm to fail is not that the match arms diverge,
// but rather that there's a prior obligation that doesn't hold.
0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
_ => (span, ObligationCauseCode::MatchExpressionArm {
_ => (expr.span, ObligationCauseCode::MatchExpressionArm {
arm_span,
source: match_src,
prior_arms: other_arms.clone(),
@ -153,7 +166,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
if other_arms.len() > 5 {
other_arms.remove(0);
}
}
arm_ty
};
prior_arm_ty = Some(arm_ty);
}
@ -185,11 +199,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
span: Span,
then_expr: &'tcx hir::Expr,
coercion: &mut CoerceMany<'tcx, '_, rustc::hir::Arm>,
) {
) -> bool {
// If this `if` expr is the parent's function return expr,
// the cause of the type coercion is the return type, point at it. (#25228)
let ret_reason = self.maybe_get_coercion_reason(then_expr.hir_id, span);
let cause = self.cause(span, ObligationCauseCode::IfExpressionWithNoElse);
let mut error = false;
coercion.coerce_forced_unit(self, &cause, &mut |err| {
if let Some((span, msg)) = &ret_reason {
err.span_label(*span, msg.as_str());
@ -200,7 +215,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
err.note("`if` expressions without `else` evaluate to `()`");
err.help("consider adding an `else` block that evaluates to the expected type");
error = true;
}, ret_reason.is_none());
error
}
fn maybe_get_coercion_reason(&self, hir_id: hir::HirId, span: Span) -> Option<(Span, String)> {

6
src/test/ui/if/if-without-else-as-fn-expr.rs
View file

@ -3,7 +3,6 @@ fn foo(bar: usize) -> usize {
return 3;
}
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
}
fn foo2(bar: usize) -> usize {
@ -11,7 +10,6 @@ fn foo2(bar: usize) -> usize {
return 3;
};
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
x
}
@ -20,7 +18,6 @@ fn foo3(bar: usize) -> usize {
3
}
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
}
fn foo_let(bar: usize) -> usize {
@ -28,7 +25,6 @@ fn foo_let(bar: usize) -> usize {
return 3;
}
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
}
fn foo2_let(bar: usize) -> usize {
@ -36,7 +32,6 @@ fn foo2_let(bar: usize) -> usize {
return 3;
};
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
x
}
@ -45,7 +40,6 @@ fn foo3_let(bar: usize) -> usize {
3
}
//~^^^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
}
// FIXME(60254): deduplicate first error in favor of second.

83
src/test/ui/if/if-without-else-as-fn-expr.stderr
View file

@ -1,14 +1,3 @@
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:2:5
|
LL | / if bar % 5 == 0 {
LL | | return 3;
LL | | }
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:2:5
|
@ -24,20 +13,8 @@ LL | | }
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:10:20
|
LL | let x: usize = if bar % 5 == 0 {
| ____________________^
LL | | return 3;
LL | | };
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:10:20
--> $DIR/if-without-else-as-fn-expr.rs:9:20
|
LL | let x: usize = if bar % 5 == 0 {
| _________-__________^
@ -52,19 +29,8 @@ LL | | };
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:19:5
|
LL | / if bar % 5 == 0 {
LL | | 3
LL | | }
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:19:5
--> $DIR/if-without-else-as-fn-expr.rs:17:5
|
LL | fn foo3(bar: usize) -> usize {
| ----- expected `usize` because of this return type
@ -78,19 +44,8 @@ LL | | }
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:27:5
|
LL | / if let 0 = 1 {
LL | | return 3;
LL | | }
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:27:5
--> $DIR/if-without-else-as-fn-expr.rs:24:5
|
LL | fn foo_let(bar: usize) -> usize {
| ----- expected `usize` because of this return type
@ -104,20 +59,8 @@ LL | | }
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:35:20
|
LL | let x: usize = if let 0 = 1 {
| ____________________^
LL | | return 3;
LL | | };
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:35:20
--> $DIR/if-without-else-as-fn-expr.rs:31:20
|
LL | let x: usize = if let 0 = 1 {
| _________-__________^
@ -132,19 +75,8 @@ LL | | };
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error[E0308]: mismatched types
--> $DIR/if-without-else-as-fn-expr.rs:44:5
|
LL | / if let 0 = 1 {
LL | | 3
LL | | }
| |_____^ expected usize, found ()
|
= note: expected type `usize`
found type `()`
error[E0317]: if may be missing an else clause
--> $DIR/if-without-else-as-fn-expr.rs:44:5
--> $DIR/if-without-else-as-fn-expr.rs:39:5
|
LL | fn foo3_let(bar: usize) -> usize {
| ----- expected `usize` because of this return type
@ -158,7 +90,6 @@ LL | | }
= note: `if` expressions without `else` evaluate to `()`
= help: consider adding an `else` block that evaluates to the expected type
error: aborting due to 12 previous errors
error: aborting due to 6 previous errors
Some errors have detailed explanations: E0308, E0317.
For more information about an error, try `rustc --explain E0308`.
For more information about this error, try `rustc --explain E0317`.

1
src/test/ui/issues/issue-50577.rs
View file

@ -2,6 +2,5 @@ fn main() {
enum Foo {
Drop = assert_eq!(1, 1)
//~^ ERROR if may be missing an else clause
//~| ERROR mismatched types [E0308]
}
}

15
src/test/ui/issues/issue-50577.stderr
View file

@ -1,13 +1,3 @@
error[E0308]: mismatched types
--> $DIR/issue-50577.rs:3:16
|
LL | Drop = assert_eq!(1, 1)
| ^^^^^^^^^^^^^^^^ expected isize, found ()
|
= note: expected type `isize`
found type `()`
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error[E0317]: if may be missing an else clause
--> $DIR/issue-50577.rs:3:16
|
@ -23,7 +13,6 @@ LL | Drop = assert_eq!(1, 1)
= help: consider adding an `else` block that evaluates to the expected type
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: aborting due to 2 previous errors
error: aborting due to previous error
Some errors have detailed explanations: E0308, E0317.
For more information about an error, try `rustc --explain E0308`.
For more information about this error, try `rustc --explain E0317`.