Sema: Assigning vars of generic param type should not use runtime metadata.

Author: jckarter

lib/Sema/TypeCheckCaptures.cpp

@@ -397,8 +397,10 @@ class FindCapturedVars : public ASTWalker {
     // doesn't require its type metadata.
     if (auto declRef = dyn_cast<DeclRefExpr>(E))
       return (!declRef->getDecl()->isObjC()
-              && !E->getType()->hasRetainablePointerRepresentation()
-              && !E->getType()->is<AnyMetatypeType>());
+              && !E->getType()->getLValueOrInOutObjectType()
+                              ->hasRetainablePointerRepresentation()
+              && !E->getType()->getLValueOrInOutObjectType()
+                              ->is<AnyMetatypeType>());
 
     // Loading classes or metatypes doesn't require their metadata.
     if (isa<LoadExpr>(E))
@@ -487,6 +489,11 @@ class FindCapturedVars : public ASTWalker {
     if (isa<ClassMetatypeToObjectExpr>(E)
         || isa<ExistentialMetatypeToObjectExpr>(E))
       return false;
+    
+    // Assigning an object doesn't require type metadata.
+    if (auto assignment = dyn_cast<AssignExpr>(E))
+      return !assignment->getSrc()->getType()
+        ->hasRetainablePointerRepresentation();
 
     return true;
   }

test/ClangModules/objc_bridging_generics.swift

@@ -212,6 +212,17 @@ extension AnimalContainer {
     y.apexPredator = x
   }
 
+  func doesntUseGenericParam5(y: T) {
+    var x = y
+    x = y
+    _ = x
+  }
+  func doesntUseGenericParam6(y: T?) {
+    var x = y
+    x = y
+    _ = x
+  }
+
   // expected-error@+1{{extension of a generic Objective-C class cannot access the class's generic parameters}}
   func usesGenericParamA(_ x: T) {
     _ = T(noise: x) // expected-note{{used here}}