[CodeGen] Fix a regression by emitting lambda expressions in EmitLValue

[erik.pilkington]

Summary

Currently, we emit a "unsupported l-value" error for the lambda expression in the following:

@interface X 
@property void (*fnptr)();
@end
void f(X *x) {
  x.fnptr = [] {};
}

This is a regression introduced in rC351487, which prevents clang from emitting lambdas in EmitLValue. This is needed though to support cases where a lambda appears as an OpaqueValueExpr of a PseudoObjectExpr.

rdar://49030379

[rjmccall]

LGTM

lib/CodeGen/CGExpr.cpp

case Expr::InitListExprClass:
     return EmitInitListLValue(cast<InitListExpr>(E));
   case Expr::CXXTemporaryObjectExprClass:
   case Expr::CXXConstructExprClass:
     return EmitCXXConstructLValue(cast<CXXConstructExpr>(E));
   case Expr::CXXBindTemporaryExprClass:
     return EmitCXXBindTemporaryLValue(cast<CXXBindTemporaryExpr>(E));
   case Expr::CXXUuidofExprClass:
     return EmitCXXUuidofLValue(cast<CXXUuidofExpr>(E));
+  case Expr::LambdaExprClass:
+    return EmitAggExprToLValue(E);
 
   case Expr::ExprWithCleanupsClass: {
     const auto *cleanups = cast<ExprWithCleanups>(E);
     enterFullExpression(cleanups);
     RunCleanupsScope Scope(*this);
     LValue LV = EmitLValue(cleanups->getSubExpr());
     if (LV.isSimple()) {
       // Defend against branches out of gnu statement expressions surrounded by

test/CodeGenObjCXX/property-lvalue-lambda.mm

+// RUN: %clang_cc1 -fblocks -disable-llvm-passes -triple x86_64-apple-darwin10 -std=c++17 -emit-llvm -o - %s | FileCheck %s
+
+typedef void (^blk_t)();
+typedef void (*fnptr_t)();
+
+@interface X
+@property blk_t blk;
+@property fnptr_t fnptr;
+@end
+
+template <class T>
+blk_t operator+(blk_t lhs, T) { return lhs; }
+
+template <class T>
+fnptr_t operator+(fnptr_t lhs, T) { return lhs; }
+
+// CHECK-LABEL: define void @_Z2t1P1X
+void t1(X *x) {
+  // Check that we call lambda.operator blk_t(), and that we send that result to
+  // the setter.
+
+  // CHECK: [[CALL:%.*]] = call void ()* @"_ZZ2t1P1XENK3$_0cvU13block_pointerFvvEEv"
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}({{.*}} void ()* [[CALL]])
+  x.blk = [] {};
+
+  // CHECK: [[CALL2:%.*]] = call void ()* @"_ZZ2t1P1XENK3$_1cvPFvvEEv"
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}({{.*}} void ()* [[CALL2]])
+  x.fnptr = [] {};
+}
+
+// CHECK-LABEL: define void @_Z2t2P1X
+void t2(X *x) {
+  // Test the case when the lambda isn't unique. (see OpaqueValueExpr::isUnique)
+  // FIXME: This asserts if the lambda isn't trivially copy/movable.
+
+  // [x setBlk: operator+([x blk], [] {})]
+
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}
+  // CHECK: [[PLUS:%.*]] = call void ()* @"_ZplIZ2t2P1XE3$_2EU13block_pointerFvvES4_T_"
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}({{.*}} [[PLUS]])
+  x.blk += [] {};
+
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}
+  // CHECK: [[PLUS:%.*]] = call void ()* @"_ZplIZ2t2P1XE3$_3EPFvvES4_T_"
+  // CHECK: call void{{.*}}@objc_msgSend{{.*}}({{.*}} [[PLUS]])
+  x.fnptr += [] {};
+}