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add tests for array/slice const patterns

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dianne 2025-04-01 21:35:12 -07:00
parent 3779c6b797
commit 7a4d4de8a8
2 changed files with 137 additions and 0 deletions
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53
tests/ui/consts/const_in_pattern/arrays-and-slices.rs Normal file
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//! Tests that arrays and slices in constants aren't interchangeable when used as patterns.
#[derive(PartialEq, Eq)]
struct SomeStruct<T: ?Sized>(T);
const BSTR_SIZED: &'static [u8; 3] = b"012";
const BSTR_UNSIZED: &'static [u8] = BSTR_SIZED;
const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED);
const STRUCT_UNSIZED: &'static SomeStruct<[u8]> = STRUCT_SIZED;
fn type_mismatches() {
// Test that array consts can't be used where a slice pattern is expected. This helps ensure
// that `const_to_pat` won't produce irrefutable `thir::PatKind::Array` patterns when matching
// on slices, which would result in missing length checks.
// See also `tests/ui/match/pattern-deref-miscompile.rs`, which tests that byte string literal
// patterns check slices' length appropriately when matching on slices.
match BSTR_UNSIZED {
BSTR_SIZED => {}
//~^ ERROR: mismatched types
_ => {}
}
match STRUCT_UNSIZED {
STRUCT_SIZED => {}
//~^ ERROR: mismatched types
_ => {}
}
// Test that slice consts can't be used where an array pattern is expected.
match BSTR_UNSIZED {
BSTR_SIZED => {}
//~^ ERROR: mismatched types
_ => {}
}
// If the types matched here, this would still error, since unsized structs aren't permitted in
// constant patterns. See the `invalid_patterns` test below.
match STRUCT_UNSIZED {
STRUCT_SIZED => {}
//~^ ERROR: mismatched types
_ => {}
}
}
fn invalid_patterns() {
// Test that unsized structs containing slices can't be used as patterns.
// See `tests/ui/consts/issue-87046.rs` for an example with `str`.
match STRUCT_UNSIZED {
STRUCT_UNSIZED => {}
//~^ ERROR: cannot use unsized non-slice type `SomeStruct<[u8]>` in constant patterns
_ => {}
}
}
fn main() {}

84
tests/ui/consts/const_in_pattern/arrays-and-slices.stderr Normal file
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error[E0308]: mismatched types
--> $DIR/arrays-and-slices.rs:18:9
|
LL | const BSTR_SIZED: &'static [u8; 3] = b"012";
| ---------------------------------- constant defined here
...
LL | match BSTR_UNSIZED {
| ------------ this expression has type `&[u8]`
LL | BSTR_SIZED => {}
| ^^^^^^^^^^
| |
| expected `&[u8]`, found `&[u8; 3]`
| `BSTR_SIZED` is interpreted as a constant, not a new binding
| help: introduce a new binding instead: `other_bstr_sized`
|
= note: expected reference `&[u8]`
found reference `&'static [u8; 3]`
error[E0308]: mismatched types
--> $DIR/arrays-and-slices.rs:23:9
|
LL | const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED);
| ------------------------------------------------ constant defined here
...
LL | match STRUCT_UNSIZED {
| -------------- this expression has type `&SomeStruct<[u8]>`
LL | STRUCT_SIZED => {}
| ^^^^^^^^^^^^
| |
| expected `&SomeStruct<[u8]>`, found `&SomeStruct<[u8; 3]>`
| `STRUCT_SIZED` is interpreted as a constant, not a new binding
| help: introduce a new binding instead: `other_struct_sized`
|
= note: expected reference `&SomeStruct<[u8]>`
found reference `&'static SomeStruct<[u8; 3]>`
error[E0308]: mismatched types
--> $DIR/arrays-and-slices.rs:30:9
|
LL | const BSTR_SIZED: &'static [u8; 3] = b"012";
| ---------------------------------- constant defined here
...
LL | match BSTR_UNSIZED {
| ------------ this expression has type `&[u8]`
LL | BSTR_SIZED => {}
| ^^^^^^^^^^
| |
| expected `&[u8]`, found `&[u8; 3]`
| `BSTR_SIZED` is interpreted as a constant, not a new binding
| help: introduce a new binding instead: `other_bstr_sized`
|
= note: expected reference `&[u8]`
found reference `&'static [u8; 3]`
error[E0308]: mismatched types
--> $DIR/arrays-and-slices.rs:37:9
|
LL | const STRUCT_SIZED: &'static SomeStruct<[u8; 3]> = &SomeStruct(*BSTR_SIZED);
| ------------------------------------------------ constant defined here
...
LL | match STRUCT_UNSIZED {
| -------------- this expression has type `&SomeStruct<[u8]>`
LL | STRUCT_SIZED => {}
| ^^^^^^^^^^^^
| |
| expected `&SomeStruct<[u8]>`, found `&SomeStruct<[u8; 3]>`
| `STRUCT_SIZED` is interpreted as a constant, not a new binding
| help: introduce a new binding instead: `other_struct_sized`
|
= note: expected reference `&SomeStruct<[u8]>`
found reference `&'static SomeStruct<[u8; 3]>`
error: cannot use unsized non-slice type `SomeStruct<[u8]>` in constant patterns
--> $DIR/arrays-and-slices.rs:47:9
|
LL | const STRUCT_UNSIZED: &'static SomeStruct<[u8]> = STRUCT_SIZED;
| ----------------------------------------------- constant defined here
...
LL | STRUCT_UNSIZED => {}
| ^^^^^^^^^^^^^^
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0308`.