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