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Rollup merge of #102016 - lcnr:given-OutlivesEnvironment, r=jackh726

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implied_bounds: deal with inference vars

fixes #101951

while computing implied bounds for `<<T as ConstructionFirm>::Builder as BuilderFn<'_>>::Output` normalization replaces a projection with an inference var (adding a `Projection` obligation). Until we prove that obligation, this inference var remains unknown, which caused us to miss an implied bound necessary to prove that the unnormalized projection from the trait method signature is wf.

r? types
This commit is contained in:
Matthias Krüger 2022-09-25 09:32:07 +02:00 • committed by GitHub
commit 16de1fddee
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5 changed files with 91 additions and 34 deletions
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3
compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
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@ -46,7 +46,7 @@ impl<'a, 'cx, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'cx, 'tcx> {
/// Note that this may cause outlives obligations to be injected
/// into the inference context with this body-id.
/// - `ty`, the type that we are supposed to assume is WF.
#[instrument(level = "debug", skip(self, param_env, body_id))]
#[instrument(level = "debug", skip(self, param_env, body_id), ret)]
fn implied_outlives_bounds(
&self,
param_env: ty::ParamEnv<'tcx>,
@ -71,6 +71,7 @@ impl<'a, 'cx, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'cx, 'tcx> {
let TypeOpOutput { output, constraints, .. } = result;
if let Some(constraints) = constraints {
debug!(?constraints);
// Instantiation may have produced new inference variables and constraints on those
// variables. Process these constraints.
let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(self.tcx);