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Tweak output of type mismatch between "then" and else if arms

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This commit is contained in:
Esteban Küber 2019-01-06 13:37:03 -08:00
parent 9aee7ed335
commit 7fc1685c47
10 changed files with 238 additions and 13 deletions
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8
src/librustc/infer/error_reporting/mod.rs
View File

@ -511,6 +511,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
}
}
},
ObligationCauseCode::IfExpression { then, outer } => {
err.span_label(then, "expected because of this");
outer.map(|sp| err.span_label(sp, "if and else have incompatible types"));
}
_ => (),
}
}
@ -1460,7 +1464,7 @@ impl<'tcx> ObligationCause<'tcx> {
}
_ => "match arms have incompatible types",
}),
IfExpression => Error0308("if and else have incompatible types"),
IfExpression { .. } => Error0308("if and else have incompatible types"),
IfExpressionWithNoElse => Error0317("if may be missing an else clause"),
MainFunctionType => Error0580("main function has wrong type"),
StartFunctionType => Error0308("start function has wrong type"),
@ -1488,7 +1492,7 @@ impl<'tcx> ObligationCause<'tcx> {
hir::MatchSource::IfLetDesugar { .. } => "`if let` arms have compatible types",
_ => "match arms have compatible types",
},
IfExpression => "if and else have compatible types",
IfExpression { .. } => "if and else have compatible types",
IfExpressionWithNoElse => "if missing an else returns ()",
MainFunctionType => "`main` function has the correct type",
StartFunctionType => "`start` function has the correct type",

2
src/librustc/traits/error_reporting.rs
View File

@ -1445,7 +1445,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
ObligationCauseCode::ExprAssignable |
ObligationCauseCode::MatchExpressionArm { .. } |
ObligationCauseCode::MatchExpressionArmPattern { .. } |
ObligationCauseCode::IfExpression |
ObligationCauseCode::IfExpression { .. } |
ObligationCauseCode::IfExpressionWithNoElse |
ObligationCauseCode::MainFunctionType |
ObligationCauseCode::StartFunctionType |

5
src/librustc/traits/mod.rs
View File

@ -229,7 +229,10 @@ pub enum ObligationCauseCode<'tcx> {
MatchExpressionArmPattern { span: Span, ty: Ty<'tcx> },
/// Computing common supertype in an if expression
IfExpression,
IfExpression {
then: Span,
outer: Option<Span>,
},
/// Computing common supertype of an if expression with no else counter-part
IfExpressionWithNoElse,

2
src/librustc/traits/structural_impls.rs
View File

@ -520,7 +520,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
super::MatchExpressionArmPattern { span, ty } => {
tcx.lift(&ty).map(|ty| super::MatchExpressionArmPattern { span, ty })
}
super::IfExpression => Some(super::IfExpression),
super::IfExpression { then, outer } => Some(super::IfExpression { then, outer }),
super::IfExpressionWithNoElse => Some(super::IfExpressionWithNoElse),
super::MainFunctionType => Some(super::MainFunctionType),
super::StartFunctionType => Some(super::StartFunctionType),

88
src/librustc_typeck/check/mod.rs
View File

@ -3366,7 +3366,93 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
let coerce_to_ty = expected.coercion_target_type(self, sp);
let mut coerce: DynamicCoerceMany = CoerceMany::new(coerce_to_ty);
let if_cause = self.cause(sp, ObligationCauseCode::IfExpression);
let mut outer_sp = if self.tcx.sess.source_map().is_multiline(sp) {
// The `if`/`else` isn't in one line in the output, include some context to make it
// clear it is an if/else expression:
// ```
// LL | let x = if true {
// | _____________-
// LL || 10i32
// || ----- expected because of this
// LL || } else {
// LL || 10u32
// || ^^^^^ expected i32, found u32
// LL || };
// ||_____- if and else have incompatible types
// ```
Some(sp)
} else {
// The entire expression is in one line, only point at the arms
// ```
// LL | let x = if true { 10i32 } else { 10u32 };
// | ----- ^^^^^ expected i32, found u32
// | |
// | expected because of this
// ```
None
};
let error_sp = opt_else_expr.map(|expr| {
if let ExprKind::Block(block, _) = &expr.node {
if let Some(expr) = &block.expr {
expr.span
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
stmt.span
} else { // empty block, point at its entirety
// Avoid overlapping spans that aren't as readable:
// ```
// 2 | let x = if true {
// | _____________-
// 3 | | 3
// | | - expected because of this
// 4 | | } else {
// | |____________^
// 5 | ||
// 6 | || };
// | || ^
// | ||_____|
// | |______if and else have incompatible types
// | expected integer, found ()
// ```
// by not pointing at the entire expression:
// ```
// 2 | let x = if true {
// | ------- if and else have incompatible types
// 3 | 3
// | - expected because of this
// 4 | } else {
// | ____________^
// 5 | |
// 6 | | };
// | |_____^ expected integer, found ()
// ```
if outer_sp.is_some() {
outer_sp = Some(self.tcx.sess.source_map().def_span(sp));
}
expr.span
}
} else { // shouldn't happen unless the parser has done something weird
expr.span
}
}).unwrap_or(sp); // shouldn't be needed
let then_sp = if let ExprKind::Block(block, _) = &then_expr.node {
if let Some(expr) = &block.expr {
expr.span
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
stmt.span
} else { // empty block, point at its entirety
outer_sp = None; // same as in `error_sp`, cleanup output
then_expr.span
}
} else { // shouldn't happen unless the parser has done something weird
then_expr.span
};
let if_cause = self.cause(error_sp, ObligationCauseCode::IfExpression {
then: then_sp,
outer: outer_sp,
});
coerce.coerce(self, &if_cause, then_expr, then_ty);
if let Some(else_expr) = opt_else_expr {

34
src/test/ui/if-else-type-mismatch.rs Normal file
View File

@ -0,0 +1,34 @@
fn main() {
let _ = if true {
42i32
} else {
42u32
};
//~^^ ERROR if and else have incompatible types
let _ = if true { 42i32 } else { 42u32 };
//~^ ERROR if and else have incompatible types
let _ = if true {
42i32;
} else {
42u32
};
//~^^ ERROR if and else have incompatible types
let _ = if true {
42i32
} else {
42u32;
};
//~^^ ERROR if and else have incompatible types
let _ = if true {
} else {
42u32
};
//~^^ ERROR if and else have incompatible types
let _ = if true {
42i32
} else {
};
//~^^^ ERROR if and else have incompatible types
}

92
src/test/ui/if-else-type-mismatch.stderr Normal file
View File

@ -0,0 +1,92 @@
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:5:9
|
LL | let _ = if true {
| _____________-
LL | | 42i32
| | ----- expected because of this
LL | | } else {
LL | | 42u32
| | ^^^^^ expected i32, found u32
LL | | };
| |_____- if and else have incompatible types
|
= note: expected type `i32`
found type `u32`
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:8:38
|
LL | let _ = if true { 42i32 } else { 42u32 };
| ----- ^^^^^ expected i32, found u32
| |
| expected because of this
|
= note: expected type `i32`
found type `u32`
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:13:9
|
LL | let _ = if true {
| _____________-
LL | | 42i32;
| | ------ expected because of this
LL | | } else {
LL | | 42u32
| | ^^^^^ expected (), found u32
LL | | };
| |_____- if and else have incompatible types
|
= note: expected type `()`
found type `u32`
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:19:9
|
LL | let _ = if true {
| _____________-
LL | | 42i32
| | ----- expected because of this
LL | | } else {
LL | | 42u32;
| | ^^^^^^ expected i32, found ()
LL | | };
| |_____- if and else have incompatible types
|
= note: expected type `i32`
found type `()`
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:25:9
|
LL | let _ = if true {
| _____________________-
LL | |
LL | | } else {
| |_____- expected because of this
LL | 42u32
| ^^^^^ expected (), found u32
|
= note: expected type `()`
found type `u32`
error[E0308]: if and else have incompatible types
--> $DIR/if-else-type-mismatch.rs:30:12
|
LL | let _ = if true {
| ------- if and else have incompatible types
LL | 42i32
| ----- expected because of this
LL | } else {
| ____________^
LL | |
LL | | };
| |_____^ expected i32, found ()
|
= note: expected type `i32`
found type `()`
error: aborting due to 6 previous errors
For more information about this error, try `rustc --explain E0308`.

6
src/test/ui/if/if-branch-types.stderr
View File

@ -1,8 +1,10 @@
error[E0308]: if and else have incompatible types
--> $DIR/if-branch-types.rs:2:13
--> $DIR/if-branch-types.rs:2:38
|
LL | let x = if true { 10i32 } else { 10u32 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected i32, found u32
| ----- ^^^^^ expected i32, found u32
| |
| expected because of this
|
= note: expected type `i32`
found type `u32`

8
src/test/ui/regions/region-invariant-static-error-reporting.stderr
View File

@ -1,13 +1,15 @@
error[E0308]: if and else have incompatible types
--> $DIR/region-invariant-static-error-reporting.rs:14:15
--> $DIR/region-invariant-static-error-reporting.rs:17:9
|
LL | let bad = if x.is_some() {
| _______________^
| _______________-
LL | | x.unwrap()
| | ---------- expected because of this
LL | | } else {
LL | | mk_static()
| | ^^^^^^^^^^^ lifetime mismatch
LL | | };
| |_____^ lifetime mismatch
| |_____- if and else have incompatible types
|
= note: expected type `Invariant<'a>`
found type `Invariant<'static>`

6
src/test/ui/str/str-array-assignment.stderr
View File

@ -1,8 +1,10 @@
error[E0308]: if and else have incompatible types
--> $DIR/str-array-assignment.rs:3:11
--> $DIR/str-array-assignment.rs:3:37
|
LL | let t = if true { s[..2] } else { s };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected str, found &str
| ------ ^ expected str, found &str
| |
| expected because of this
|
= note: expected type `str`
found type `&str`