[modules] Defer merging deduced return types.

We can't read a deduced return type until we are sure that the types referred
to by it are not in the middle of being loaded. So defer all reading of such
deduced return types until the end of the recursive deserialization step.

Also, when we load a function type that has a deduced return type, update all
other redeclarations of the function to have that deduced return type.

llvm-svn: 338798

2 files changed, 9 insertions, 0 deletions

diff --git a/clang/test/Modules/merge-deduced-return.cpp b/clang/test/Modules/merge-deduced-return.cpp
index 0a4de7b9755..71dc29b633b 100644
--- a/clang/test/Modules/merge-deduced-return.cpp
+++ b/clang/test/Modules/merge-deduced-return.cpp
@@ -8,6 +8,8 @@ module A {}
 #pragma clang module begin A
 inline auto f() { struct X {}; return X(); }
 inline auto a = f();
+auto g(int);
+template<typename T> auto h(T t) { return g(t); }
 #pragma clang module end
 #pragma clang module endbuild
 
@@ -17,12 +19,14 @@ module B {}
 #pragma clang module begin B
 inline auto f() { struct X {}; return X(); }
 inline auto b = f();
+auto g(int) { return 0; }
 #pragma clang module end
 #pragma clang module endbuild
 
 #ifdef LOCAL
 inline auto f() { struct X {}; return X(); }
 inline auto b = f();
+auto g(int) { return 0; }
 #else
 #pragma clang module import B
 #endif
@@ -31,3 +35,5 @@ inline auto b = f();
 
 using T = decltype(a);
 using T = decltype(b);
+
+int test_g = h(0);
diff --git a/clang/test/Modules/merge-lambdas.cpp b/clang/test/Modules/merge-lambdas.cpp
index 8b3b5013284..463a4c9b2fc 100644
--- a/clang/test/Modules/merge-lambdas.cpp
+++ b/clang/test/Modules/merge-lambdas.cpp
@@ -46,3 +46,6 @@ using U = decltype(y2);
 
 using V = decltype(x3);
 using V = decltype(y3);
+
+#pragma clang module import A
+void (*p)() = f<int>();