Propagate Expectation around binop typeck code to construct more precise trait obligations for binops.

2 files changed, 20 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index d8cc7d3feb0..945cdfbb0e9 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -12,7 +12,7 @@ pub mod util;
 use crate::infer::canonical::Canonical;
 use crate::ty::abstract_const::NotConstEvaluatable;
 use crate::ty::subst::SubstsRef;
-use crate::ty::{self, AdtKind, Ty, TyCtxt};
+use crate::ty::{self, AdtKind, Predicate, Ty, TyCtxt};
 
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, Diagnostic};
@@ -414,6 +414,7 @@ pub enum ObligationCauseCode<'tcx> {
     BinOp {
         rhs_span: Option<Span>,
         is_lit: bool,
+        output_pred: Option<Predicate<'tcx>>,
     },
 }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index f0acb02933a..3536d946db2 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1033,6 +1033,24 @@ impl<'tcx> Predicate<'tcx> {
         }
     }
 
+    pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
+        let predicate = self.kind();
+        match predicate.skip_binder() {
+            PredicateKind::Projection(t) => Some(predicate.rebind(t)),
+            PredicateKind::Trait(..)
+            | PredicateKind::Subtype(..)
+            | PredicateKind::Coerce(..)
+            | PredicateKind::RegionOutlives(..)
+            | PredicateKind::WellFormed(..)
+            | PredicateKind::ObjectSafe(..)
+            | PredicateKind::ClosureKind(..)
+            | PredicateKind::TypeOutlives(..)
+            | PredicateKind::ConstEvaluatable(..)
+            | PredicateKind::ConstEquate(..)
+            | PredicateKind::TypeWellFormedFromEnv(..) => None,
+        }
+    }
+
     pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
         let predicate = self.kind();
         match predicate.skip_binder() {