0138151c21
Improve handling of expressions in patterns Closes #112593. Methodcalls' dots in patterns are silently recovered as commas (e.g. `Foo("".len())` -> `Foo("", len())`) so extra diagnostics are emitted: ```rs struct Foo(u8, String, u8); fn bar(foo: Foo) -> bool { match foo { Foo(4, "yippee".yeet(), 7) => true, _ => false } } ``` ``` error: expected one of `)`, `,`, `...`, `..=`, `..`, or `|`, found `.` --> main.rs:5:24 | 5 | Foo(4, "yippee".yeet(), 7) => true, | ^ | | | expected one of `)`, `,`, `...`, `..=`, `..`, or `|` | help: missing `,` error[E0531]: cannot find tuple struct or tuple variant `yeet` in this scope --> main.rs:5:25 | 5 | Foo(4, "yippee".yeet(), 7) => true, | ^^^^ not found in this scope error[E0023]: this pattern has 4 fields, but the corresponding tuple struct has 3 fields --> main.rs:5:13 | 1 | struct Foo(u8, String, u8); | -- ------ -- tuple struct has 3 fields ... 5 | Foo(4, "yippee".yeet(), 7) => true, | ^ ^^^^^^^^ ^^^^^^ ^ expected 3 fields, found 4 error: aborting due to 3 previous errors ``` This PR checks for patterns that ends with a dot and a lowercase ident (as structs/variants should be uppercase): ``` error: expected a pattern, found a method call --> main.rs:5:16 | 5 | Foo(4, "yippee".yeet(), 7) => true, | ^^^^^^^^^^^^^^^ method calls are not allowed in patterns error: aborting due to 1 previous error ``` Also check for expressions: ```rs fn is_idempotent(x: f32) -> bool { match x { x * x => true, _ => false, } } fn main() { let mut t: [i32; 5]; let t[0] = 1; } ``` ``` error: expected a pattern, found an expression --> main.rs:3:9 | 3 | x * x => true, | ^^^^^ arbitrary expressions are not allowed in patterns error: expected a pattern, found an expression --> main.rs:10:9 | 10 | let t[0] = 1; | ^^^^ arbitrary expressions are not allowed in patterns ``` Would be cool if the compiler could suggest adding a guard for `match`es, but I've no idea how to do it. --- `@rustbot` label +A-diagnostics +A-parser +A-patterns +C-enhancement
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