Implement return type deduction for lambdas per C++11

[expr.prim.lambda]p4, including the current suggested resolution of
core isue 975, which allows multiple return statements so long as the
types match. ExtWarn when user code is actually making use of this
extension.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150168 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 42 insertions, 0 deletions

diff --git a/test/CXX/expr/expr.prim/expr.prim.lambda/p4.cpp b/test/CXX/expr/expr.prim/expr.prim.lambda/p4.cpp
new file mode 100644
index 0000000000..a3a29c0977
--- /dev/null
+++ b/test/CXX/expr/expr.prim/expr.prim.lambda/p4.cpp
@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 %s -verify
+
+void missing_lambda_declarator() {
+  [](){}();
+}
+
+template<typename T> T get();
+
+void infer_void_return_type(int i) {
+  if (i > 17)
+    return []() { }();
+
+  if (i > 11)
+    return []() { return; }();
+
+  return [](int x) {
+    switch (x) {
+    case 0: return get<void>();
+    case 1: return;
+    }
+  }(7);
+}
+
+struct X { };
+
+X infer_X_return_type(X x) {
+  return [&x](int y) { // expected-warning{{omitted result type}}
+    if (y > 0)
+      return X();
+    else
+      return x;
+  }(5);
+}
+
+X infer_X_return_type_fail(X x) { 
+  return [x](int y) { // expected-warning{{omitted result type}}
+    if (y > 0)
+      return X();
+    else // FIXME: shouldn't mention blocks
+      return x; // expected-error{{return type 'const X' must match previous return type 'X' when block literal has unspecified explicit return type}}
+  }(5);
+}