Sema/SILGen: Do erasure from pseudogeneric T to Any without requiring runtime metadata.

Naively wrapping a T in an Any would require metadata for T, but we can go to AnyObject first and put the AnyObject in the Any without T's metadata. This fixes a regression in ObjC generic extension methods when they try to pass their generic parameters to id parameters as Any. rdar://problem/27526877

Author: jckarter

lib/SILGen/SILGenConvert.cpp

@@ -654,6 +654,40 @@ ManagedValue SILGenFunction::emitExistentialErasure(
     return emitManagedRValueWithCleanup(existential);
   }
   case ExistentialRepresentation::Opaque: {
+  
+    // If the concrete value is a pseudogeneric archetype, first erase it to
+    // its upper bound.
+    auto anyObjectProto = getASTContext()
+      .getProtocol(KnownProtocolKind::AnyObject);
+    auto anyObjectTy = anyObjectProto
+      ? anyObjectProto->getDeclaredType()->getCanonicalType()
+      : CanType();
+    auto eraseToAnyObject =
+    [&, concreteFormalType, F](SGFContext C) -> ManagedValue {
+      auto concreteValue = F(SGFContext());
+      auto anyObjectConformance = SGM.SwiftModule
+        ->lookupConformance(concreteFormalType, anyObjectProto, nullptr);
+      ProtocolConformanceRef buf[] = {
+        *anyObjectConformance,
+      };
+      
+      auto asAnyObject = B.createInitExistentialRef(loc,
+                                  SILType::getPrimitiveObjectType(anyObjectTy),
+                                  concreteFormalType,
+                                  concreteValue.getValue(),
+                                  getASTContext().AllocateCopy(buf));
+      return ManagedValue(asAnyObject, concreteValue.getCleanup());
+    };
+    
+    auto concreteTLPtr = &concreteTL;
+    if (this->F.getLoweredFunctionType()->isPseudogeneric()) {
+      if (anyObjectTy && concreteFormalType->is<ArchetypeType>()) {
+        concreteFormalType = anyObjectTy;
+        concreteTLPtr = &getTypeLowering(anyObjectTy);
+        F = eraseToAnyObject;
+      }
+    }
+
     // Allocate the existential.
     SILValue existential =
       getBufferForExprResult(loc, existentialTL.getLoweredType(), C);
@@ -662,7 +696,7 @@ ManagedValue SILGenFunction::emitExistentialErasure(
     SILValue valueAddr = B.createInitExistentialAddr(
                             loc, existential,
                             concreteFormalType,
-                            concreteTL.getLoweredType(),
+                            concreteTLPtr->getLoweredType(),
                             conformances);
     // Initialize the concrete value in-place.
     InitializationPtr init(

lib/Sema/TypeCheckCaptures.cpp

@@ -477,13 +477,22 @@ class FindCapturedVars : public ASTWalker {
       if (E->getType()->isObjCExistentialType()
           || E->getType()->is<AnyMetatypeType>())
         return false;
+      
+      // We also special case Any erasure in pseudogeneric contexts
+      // not to rely on concrete type metadata by erasing from AnyObject
+      // as a waypoint.
+      if (E->getType()->isAny()
+          && erasure->getSubExpr()->getType()->is<ArchetypeType>())
+        return false;
+
       // Erasure to a Swift protocol always captures the type metadata from
       // its subexpression.
       checkType(erasure->getSubExpr()->getType(),
                 erasure->getSubExpr()->getLoc());
       return true;
     }
 
+    
     // Converting an @objc metatype to AnyObject doesn't require type
     // metadata.
     if (isa<ClassMetatypeToObjectExpr>(E)

test/ClangModules/objc_bridging_generics.swift

@@ -133,9 +133,8 @@ extension GenericClass {
   func usesGenericParamG(_ x: T) {
     _ = T.self // expected-note{{used here}}
   }
-  // expected-error@+1{{extension of a generic Objective-C class cannot access the class's generic parameters}}
-  func usesGenericParamH(_ x: T) {
-    _ = x as Any // expected-note{{used here}}
+  func doesntUseGenericParamH(_ x: T) {
+    _ = x as Any
   }
   // expected-error@+1{{extension of a generic Objective-C class cannot access the class's generic parameters}}
   func usesGenericParamI(_ y: T.Type) {
@@ -181,14 +180,13 @@ extension AnimalContainer {
     _ = #selector(y.create)
   }
 
-  // TODO: 'Any' bridging should not require reifying generic params.
-  func doesntUseGenericParam2(_ x: T, _ y: T.Type) { // expected-error{{cannot access the class's generic parameters}}
+  func doesntUseGenericParam2(_ x: T, _ y: T.Type) {
     let a = x.another()
     _ = a.another()
     _ = x.another().another()
 
     _ = type(of: x).create().another()
-    _ = type(of: x).init(noise: x).another() // expected-note{{here}}
+    _ = type(of: x).init(noise: x).another()
     _ = y.create().another()
     _ = y.init(noise: x).another()
     _ = y.init(noise: x.another()).another()
@@ -257,9 +255,8 @@ extension AnimalContainer {
 }
 
 extension PettableContainer {
-  // TODO: Any erasure shouldn't use generic parameter metadata.
-  func doesntUseGenericParam(_ x: T, _ y: T.Type) { // expected-error{{cannot access the class's generic parameters}}
-    _ = type(of: x).init(fur: x).other() // expected-note{{here}}
+  func doesntUseGenericParam(_ x: T, _ y: T.Type) {
+    _ = type(of: x).init(fur: x).other()
     _ = type(of: x).adopt().other()
     _ = y.init(fur: x).other()
     _ = y.adopt().other()

test/SILGen/objc_bridging_any.swift

@@ -2,6 +2,7 @@
 // REQUIRES: objc_interop
 
 import Foundation
+import objc_generics
 
 protocol P {}
 protocol CP: class {}
@@ -498,3 +499,13 @@ func dynamicLookup(x: AnyObject) {
   _ = x.anyProperty
   _ = x[IndexForAnySubscript()]
 }
+
+extension GenericClass {
+  // CHECK-LABEL: sil hidden @_TFE17objc_bridging_anyCSo12GenericClass23pseudogenericAnyErasurefT1xx_P_
+  func pseudogenericAnyErasure(x: T) -> Any {
+    // CHECK: [[ANY_BUF:%.*]] = init_existential_addr %0 : $*Any, $AnyObject
+    // CHECK: [[ANYOBJECT:%.*]] = init_existential_ref %1 : $T : $T, $AnyObject
+    // CHECK: store [[ANYOBJECT]] to [[ANY_BUF]]
+    return x
+  }
+}