Point at enum definition when match patterns are not exhaustive #58380
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| @@ -204,25 +204,42 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> { | |||
| // is uninhabited. | |||
| let pat_ty = self.tables.node_id_to_type(scrut.hir_id); | |||
| let module = self.tcx.hir().get_module_parent(scrut.id); | |||
| let mut def_span = None; | |||
| let mut missing_variants = vec![]; | |||
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I usually write empty vectors as Vec::new() (thinking, "no need to the macro sugar when there aren't any elements to initialize"), but rustfmt doesn't seem to have an opinion. (I guess you could argue that it's technically a semantic change.)
| "ensure that all possible cases are being handled, \ | ||
| possibly by adding wildcards or more match arms"); | ||
| let mut err = create_e0004(self.tcx.sess, scrut.span, format!( | ||
| "non-exhaustive patterns: type `{}` is non-empty", |
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(I realized that this was already here and not a part of the present changeset, but) do we even want to bother saying "type is non-empty" here? If we don't expect users to think or care about the empty enum very often, this might not be the most helpful time to educate them.
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changed to "non-exhaustive patterns: variant Foo of type Bar is not handled"
| if def.variants.len() < 4 && !def.variants.is_empty() { | ||
| // keep around to point at the definition of non-covered variants | ||
| missing_variants = def.variants.iter() | ||
| .map(|variant| variant.ident.span) |
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Can we call the variable missing_variant_spans or similar? (I balked at err.span_label(*variant on line 241.)
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collected the variant idents instead, keeping the vector name the same
| LL | | } | ||
| | |_- `Terminator` defined here | ||
| ... | ||
| LL | match x { //~ ERROR E0004 |
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(possibly a bad idea, probably out of scope for this PR) I find it counterintuitive for the primary span of a "non-exaustive patterns" error to point to the x in match x, rather than the body of match arms. (That could get very visually cluttered, though, especially with the secondary definition-spans introduced here. Also, pointing at the discriminant does seem intuitive when it's a pattern rather than an opaque variable, as in the examples in src/test/ui/check_match/issue-35609.stderr.)
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I have the same thoughts you do, but I lay on the side of using the smallest possible primary span, for VSCode's sake.
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```
error[E0004]: non-exhaustive patterns: type `X` is non-empty
--> file.rs:9:11
|
1 | / enum X {
2 | | A,
| | - variant not covered
3 | | B,
| | - variant not covered
4 | | C,
| | - variant not covered
5 | | }
| |_- `X` defined here
...
9 | match x {
| ^
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
error[E0004]: non-exhaustive patterns: `B` and `C` not covered
--> file.rs:11:11
|
1 | / enum X {
2 | | A,
3 | | B,
4 | | C,
| | - not covered
5 | | }
| |_- `X` defined here
...
11 | match x {
| ^ patterns `C` not covered
```
When a match expression doesn't have patterns covering every variant,
point at the enum's definition span. On a best effort basis, point at the
variant(s) that are missing. This does not handle the case when the missing
pattern is due to a field's enum variants:
```
enum E1 {
A,
B,
C,
}
enum E2 {
A(E1),
B,
}
fn foo() {
match E2::A(E1::A) {
E2::A(E1::B) => {}
E2::B => {}
}
//~^ ERROR `E2::A(E1::A)` and `E2::A(E1::C)` not handled
}
```
Unify look between match with no arms and match with some missing patterns.
Fix rust-lang#37518.
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Point at enum definition when match patterns are not exhaustive
```
error[E0004]: non-exhaustive patterns: type `X` is non-empty
--> file.rs:9:11
|
1 | / enum X {
2 | | A,
| | - variant not covered
3 | | B,
| | - variant not covered
4 | | C,
| | - variant not covered
5 | | }
| |_- `X` defined here
...
9 | match x {
| ^
|
= help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
error[E0004]: non-exhaustive patterns: `B` and `C` not covered
--> file.rs:11:11
|
1 | / enum X {
2 | | A,
3 | | B,
4 | | C,
| | - not covered
5 | | }
| |_- `X` defined here
...
11 | match x {
| ^ patterns `C` not covered
```
When a match expression doesn't have patterns covering every variant,
point at the enum's definition span. On a best effort basis, point at the
variant(s) that are missing. This does not handle the case when the missing
pattern is due to a field's enum variants:
```
enum E1 {
A,
B,
C,
}
enum E2 {
A(E1),
B,
}
fn foo() {
match E2::A(E1::A) {
E2::A(E1::B) => {}
E2::B => {}
}
//~^ ERROR `E2::A(E1::A)` and `E2::A(E1::C)` not handled
}
```
Unify look between match with no arms and match with some missing patterns.
Fix #37518.
|
☀️ Test successful - checks-travis, status-appveyor |
When a match expression doesn't have patterns covering every variant,
point at the enum's definition span. On a best effort basis, point at the
variant(s) that are missing. This does not handle the case when the missing
pattern is due to a field's enum variants:
Unify look between match with no arms and match with some missing patterns.
Fix #37518.