[CSBindings] Don't infer protocol types from the base of an unresolved member chain

xedin · xedin · commit 49cc21919b69 · 2021-02-23T11:32:24.000-08:00
diff --git a/lib/Sema/CSBindings.cpp b/lib/Sema/CSBindings.cpp
@@ -1000,6 +1000,13 @@ PotentialBindings::inferFromRelational(Constraint *constraint) {
       if (!BGT || !isKnownKeyPathDecl(CS.getASTContext(), BGT->getDecl()))
         return None;
     }
+
+    // Don't allow a protocol type to get propagated from the base to the result
+    // type of a chain, Result should always be a concrete type which conforms
+    // to the protocol inferred for the base.
+    if (locator->isLastElement<LocatorPathElt::UnresolvedMemberChainResult>() &&
+        kind == AllowedBindingKind::Supertypes && type->is<ProtocolType>())
+      return None;
   }
 
   // If the source of the binding is 'OptionalObject' constraint

Original file line number	Diff line number	Diff line change
`@@ -1000,6 +1000,13 @@ PotentialBindings::inferFromRelational(Constraint *constraint) {`
`1000`	`1000`	`if (!BGT \|\| !isKnownKeyPathDecl(CS.getASTContext(), BGT->getDecl()))`
`1001`	`1001`	`return None;`
`1002`	`1002`	`}`
	`1003`	`+`
	`1004`	`+ // Don't allow a protocol type to get propagated from the base to the result`
	`1005`	`+ // type of a chain, Result should always be a concrete type which conforms`
	`1006`	`+ // to the protocol inferred for the base.`
	`1007`	`+ if (locator->isLastElement<LocatorPathElt::UnresolvedMemberChainResult>() &&`
	`1008`	`+ kind == AllowedBindingKind::Supertypes && type->is<ProtocolType>())`
	`1009`	`+ return None;`
`1003`	`1010`	`}`
`1004`	`1011`
`1005`	`1012`	`// If the source of the binding is 'OptionalObject' constraint`