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match exhaustiveness diagnostics: show a trailing comma on singleton tuple consructors in witness patterns (and clean up a little) #145234

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match exhaustiveness diagnostics: show a trailing comma on singleton tuple consructors in witness patterns (and clean up a little) #145234

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9449b78
show a trailing comma on singleton tuple constructors in witness pats
dianne Aug 10, 2025
8f649a7
clean up witness printing for tuple-like constructors
dianne Aug 10, 2025
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22 changes: 5 additions & 17 deletions compiler/rustc_pattern_analysis/src/rustc/print.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,23 +101,11 @@ pub(crate) fn write_struct_like<'tcx>(
let num_fields = variant_and_name.as_ref().map_or(subpatterns.len(), |(v, _)| v.fields.len());
if num_fields != 0 || variant_and_name.is_none() {
write!(f, "(")?;
for i in 0..num_fields {
write!(f, "{}", start_or_comma())?;

// Common case: the field is where we expect it.
if let Some(p) = subpatterns.get(i) {
if p.field.index() == i {
write!(f, "{}", p.pattern)?;
continue;
}
}

// Otherwise, we have to go looking for it.
if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) {
write!(f, "{}", p.pattern)?;
} else {
write!(f, "_")?;
}
for FieldPat { pattern, .. } in subpatterns {
write!(f, "{}{pattern}", start_or_comma())?;
}
if matches!(ty.kind(), ty::Tuple(..)) && num_fields == 1 {
write!(f, ",")?;
}
write!(f, ")")?;
}
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4 changes: 2 additions & 2 deletions tests/ui/or-patterns/exhaustiveness-non-exhaustive.rs
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I haven't added a test specifically for singleton tuple witnesses since this test included them. I could add a separate test if it would be preferable, though, to make sure it's still tested even if this test changes.

Original file line number Diff line number Diff line change
Expand Up @@ -7,11 +7,11 @@ fn main() {
(0 | 1, 2 | 3) => {}
}
match ((0u8,),) {
//~^ ERROR non-exhaustive patterns: `((4_u8..=u8::MAX))`
//~^ ERROR non-exhaustive patterns: `((4_u8..=u8::MAX,),)`
((0 | 1,) | (2 | 3,),) => {}
}
match (Some(0u8),) {
//~^ ERROR non-exhaustive patterns: `(Some(2_u8..=u8::MAX))`
//~^ ERROR non-exhaustive patterns: `(Some(2_u8..=u8::MAX),)`
(None | Some(0 | 1),) => {}
}
}
12 changes: 6 additions & 6 deletions tests/ui/or-patterns/exhaustiveness-non-exhaustive.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -11,30 +11,30 @@ LL ~ (0 | 1, 2 | 3) => {},
LL + (2_u8..=u8::MAX, _) => todo!()
|

error[E0004]: non-exhaustive patterns: `((4_u8..=u8::MAX))` not covered
error[E0004]: non-exhaustive patterns: `((4_u8..=u8::MAX,),)` not covered
--> $DIR/exhaustiveness-non-exhaustive.rs:9:11
|
LL | match ((0u8,),) {
| ^^^^^^^^^ pattern `((4_u8..=u8::MAX))` not covered
| ^^^^^^^^^ pattern `((4_u8..=u8::MAX,),)` not covered
|
= note: the matched value is of type `((u8,),)`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
|
LL ~ ((0 | 1,) | (2 | 3,),) => {},
LL + ((4_u8..=u8::MAX)) => todo!()
LL + ((4_u8..=u8::MAX,),) => todo!()
|

error[E0004]: non-exhaustive patterns: `(Some(2_u8..=u8::MAX))` not covered
error[E0004]: non-exhaustive patterns: `(Some(2_u8..=u8::MAX),)` not covered
--> $DIR/exhaustiveness-non-exhaustive.rs:13:11
|
LL | match (Some(0u8),) {
| ^^^^^^^^^^^^ pattern `(Some(2_u8..=u8::MAX))` not covered
| ^^^^^^^^^^^^ pattern `(Some(2_u8..=u8::MAX),)` not covered
|
= note: the matched value is of type `(Option<u8>,)`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
|
LL ~ (None | Some(0 | 1),) => {},
LL + (Some(2_u8..=u8::MAX)) => todo!()
LL + (Some(2_u8..=u8::MAX),) => todo!()
|

error: aborting due to 3 previous errors
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