PR45000: Let Sema::SubstParmVarDecl handle default args of lambdas in initializers

Summary:
We extend the behavior for local functions and methods of local classes
to lambdas in variable initializers. The initializer is not a separate
scope, but we treat it as such.

We also remove the (faulty) instantiation of default arguments in
TreeTransform::TransformLambdaExpr, because it doesn't do proper
initialization, and if it did, we would do it twice (and thus also emit
eventual errors twice).

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D76038

(cherry picked from commit f43859a099fa3587123717be941fa63ba8d0d4f2)

1 files changed, 13 insertions, 0 deletions

diff --git a/clang/test/SemaTemplate/instantiate-local-class.cpp b/clang/test/SemaTemplate/instantiate-local-class.cpp
index eaff4c4bbc8..550c59d6177 100644
--- a/clang/test/SemaTemplate/instantiate-local-class.cpp
+++ b/clang/test/SemaTemplate/instantiate-local-class.cpp
@@ -486,3 +486,16 @@ namespace anon_union_default_member_init {
   }
   void g() { f<int>(); }
 }
+
+namespace PR45000 {
+  template <typename T>
+  void f(int x = [](T x = nullptr) -> int { return x; }());
+  // expected-error@-1 {{cannot initialize a parameter of type 'int' with an rvalue of type 'nullptr_t'}}
+  // expected-note@-2 {{passing argument to parameter 'x' here}}
+  // expected-error@-3 {{no matching function for call}}
+  // expected-note@-4 {{candidate function not viable: requires single argument 'x', but no arguments were provided}}
+  // expected-note@-5 {{conversion candidate of type 'auto (*)(int) -> int'}}
+
+  void g() { f<int>(); }
+  // expected-note@-1 {{in instantiation of default function argument expression for 'f<int>' required here}}
+}