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authorbors[bot] <26634292+bors[bot]@users.noreply.github.com>2020-10-15 19:02:27 +0100
committerGitHub <[email protected]>2020-10-15 19:02:27 +0100
commit0d45802d671f94cb768b93a64882733396cfbe2d (patch)
treeabb91645ee84216304065bf42a959223d040814c /crates/hir_ty/src/diagnostics
parent1de202010948c94658235f7cfe9b25dda0c7ddf3 (diff)
parent0e9d1e17d6e45b44ec1a8f1430109cfc75e41241 (diff)
Merge #6220
6220: implement binary operator overloading type inference r=flodiebold a=ruabmbua Extend type inference of *binary operator expression*, by adding support for operator overloads. Before this merge request, the type inference of binary expressions could only resolve operations done on built-in primitive types. This merge requests adds a code path, which is executed in case the built-in inference could not get any results. It resolves the proper operator overload trait in *core::ops* via lang items, and then resolves the associated *Output* type. ```rust struct V2([f32; 2]); #[lang = "add"] pub trait Add<Rhs = Self> { /// The resulting type after applying the `+` operator. type Output; /// Performs the `+` operation. #[must_use] fn add(self, rhs: Rhs) -> Self::Output; } impl Add<V2> for V2 { type Output = V2; fn add(self, rhs: V2) -> V2 { let x = self.0[0] + rhs.0[0]; let y = self.0[1] + rhs.0[1]; V2([x, y]) } } fn test() { let va = V2([0.0, 1.0]); let vb = V2([0.0, 1.0]); let r = va + vb; // This infers to V2 now } ``` There is a problem with operator overloads, which do not explicitly set the *Rhs* type parameter in the respective impl block. **Example:** ```rust impl Add for V2 { type Output = V2; fn add(self, rhs: V2) -> V2 { let x = self.0[0] + rhs.0[0]; let y = self.0[1] + rhs.0[1]; V2([x, y]) } } ``` In this case, the trait solver does not realize, that the *Rhs* type parameter is actually self in the context of the impl block. This stops type inference in its tracks, and it can not resolve the associated *Output* type. I guess we can still merge this back, because it increases the amount of resolved types, and does not regress anything (in the tests). Somewhat blocked by https://github.com/rust-analyzer/rust-analyzer/issues/5685 Resolves https://github.com/rust-analyzer/rust-analyzer/issues/5544 Co-authored-by: Roland Ruckerbauer <[email protected]>
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