1 // Regression test for #67037.
3 // In type checking patterns, E0023 occurs when the tuple pattern and the expected
4 // tuple pattern have different number of fields. For example, as below, `P()`,
5 // the tuple struct pattern, has 0 fields, but requires 1 field.
7 // In emitting E0023, we try to see if this is a case of e.g., `Some(a, b, c)` but where
8 // the scrutinee was of type `Some((a, b, c))`, and suggest that parentheses be added.
10 // However, we did not account for the expected type being different than the tuple pattern type.
11 // This caused an issue when the tuple pattern type (`P<T>`) was generic.
12 // Specifically, we tried deriving the 0th field's type using the `substs` of the expected type.
13 // When attempting to substitute `T`, there was no such substitution, so "out of range" occurred.
15 struct U {} // 0 type parameters offered
16 struct P<T>(T); // 1 type parameter wanted
19 let P() = U {}; //~ ERROR mismatched types
20 //~^ ERROR this pattern has 0 fields, but the corresponding tuple struct has 1 field