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Shallow resolve ty vars to their root var #147193

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Shallow resolve ty vars to their root var #147193

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699d3e4
shallow resolve to root var
BoxyUwU Sep 30, 2025
d821286
test
BoxyUwU Sep 30, 2025
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4 changes: 3 additions & 1 deletion compiler/rustc_infer/src/infer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1125,7 +1125,9 @@ impl<'tcx> InferCtxt<'tcx> {
// Note: if these two lines are combined into one we get
// dynamic borrow errors on `self.inner`.
let known = self.inner.borrow_mut().type_variables().probe(v).known();
known.map_or(ty, |t| self.shallow_resolve(t))
known.map_or(Ty::new_var(self.tcx, self.root_var(v)), |t| {
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Use map_or_else to only look up the root var if it's actually going to be used

self.shallow_resolve(t)
})
}

ty::IntVar(v) => {
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3 changes: 3 additions & 0 deletions tests/ui/coercion/issue-88097.rs
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Expand Up @@ -3,6 +3,9 @@
// behavior has been fixed.

//@ check-pass
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver

fn peculiar() -> impl Fn(u8) -> u8 {
return |x| x + 1
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