bjoernager/rust
bjoernager/rust
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review + some small stuff

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lcnr 2023-03-30 11:49:06 +02:00
parent 2186847f28
commit 3fab7f7c13
7 changed files with 52 additions and 14 deletions
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16
compiler/rustc_middle/src/traits/solve.rs
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@ -56,9 +56,19 @@ pub enum Certainty {
impl Certainty {
pub const AMBIGUOUS: Certainty = Certainty::Maybe(MaybeCause::Ambiguity);
/// When proving multiple goals using **AND**, e.g. nested obligations for an impl,
/// use this function to unify the certainty of these goals
pub fn unify_and(self, other: Certainty) -> Certainty {
/// Use this function to merge the certainty of multiple nested subgoals.
///
/// Given an impl like `impl<T: Foo + Bar> Baz for T {}`, we have 2 nested
/// subgoals whenever we use the impl as a candidate: `T: Foo` and `T: Bar`.
/// If evaluating `T: Foo` results in ambiguity and `T: Bar` results in
/// success, we merge these two responses. This results in ambiguity.
///
/// If we unify ambiguity with overflow, we return overflow. This doesn't matter
/// inside of the solver as we distinguish ambiguity from overflow. It does
/// however matter for diagnostics. If `T: Foo` resulted in overflow and `T: Bar`
/// in ambiguity without changing the inference state, we still want to tell the
/// user that `T: Baz` results in overflow.
pub fn unify_with(self, other: Certainty) -> Certainty {
match (self, other) {
(Certainty::Yes, Certainty::Yes) => Certainty::Yes,
(Certainty::Yes, Certainty::Maybe(_)) => other,