[Modules] Allow missing header before a missing requirement

And make the module unavailable without breaking any parent modules.

If there's a missing requirement after we've already seen a missing
header, still update the IsMissingRequiement bit correctly.  Also,
diagnose missing requirements before missing headers, since the
existence of the header is moot if there are missing requirements.

llvm-svn: 242055

2 files changed, 15 insertions, 0 deletions

diff --git a/clang/test/Modules/Inputs/module.map b/clang/test/Modules/Inputs/module.map
index ffaa53e18e2..904c65c2dbf 100644
--- a/clang/test/Modules/Inputs/module.map
+++ b/clang/test/Modules/Inputs/module.map
@@ -336,3 +336,14 @@ module ImportNameInDir {
   header "ImportNameInDir.h"
   export *
 }
+
+module RequiresWithMissingHeader {
+  module HeaderBefore {
+    header "RequiresWithMissingHeader-Missing1.h"
+    requires missing
+  }
+  module HeaderAfter {
+    requires missing
+    header "RequiresWithMissingHeader-Missing2.h"
+  }
+}
diff --git a/clang/test/Modules/requires.m b/clang/test/Modules/requires.m
index 155c6aec5dc..1a013727108 100644
--- a/clang/test/Modules/requires.m
+++ b/clang/test/Modules/requires.m
@@ -6,3 +6,7 @@
 @import DependsOnModule.NotObjC; // expected-error{{module 'DependsOnModule.NotObjC' is incompatible with feature 'objc'}}
 @import DependsOnModule.CustomReq1; // OK
 @import DependsOnModule.CustomReq2; // expected-error{{module 'DependsOnModule.CustomReq2' requires feature 'custom_req2'}}
+
+@import RequiresWithMissingHeader; // OK
+@import RequiresWithMissingHeader.HeaderBefore; // expected-error{{module 'RequiresWithMissingHeader.HeaderBefore' requires feature 'missing'}}
+@import RequiresWithMissingHeader.HeaderAfter; // expected-error{{module 'RequiresWithMissingHeader.HeaderAfter' requires feature 'missing'}}