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fix: Allow inferring array sizes #21061

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Merged
merged 1 commit into from
Nov 19, 2025
Merged

fix: Allow inferring array sizes #21061

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12 changes: 8 additions & 4 deletions crates/hir-ty/src/infer/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1336,14 +1336,18 @@ impl<'db> InferenceContext<'_, 'db> {
ExprIsRead::Yes,
);
let usize = self.types.usize;
match self.body[repeat] {
let len = match self.body[repeat] {
Expr::Underscore => {
self.write_expr_ty(repeat, usize);
self.table.next_const_var()
}
_ => _ = self.infer_expr(repeat, &Expectation::HasType(usize), ExprIsRead::Yes),
}
_ => {
self.infer_expr(repeat, &Expectation::HasType(usize), ExprIsRead::Yes);
consteval::eval_to_const(repeat, self)
}
};

(elem_ty, consteval::eval_to_const(repeat, self))
(elem_ty, len)
}
};
// Try to evaluate unevaluated constant, and insert variable if is not possible.
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13 changes: 13 additions & 0 deletions crates/hir-ty/src/tests/simple.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3943,3 +3943,16 @@ fn foo() {
"#]],
);
}

#[test]
fn infer_array_size() {
check_no_mismatches(
r#"
fn foo(a: [u8; 3]) {}

fn bar() {
foo([0; _]);
}
"#,
);
}