[ASTUnit] Fix a regression in cached completions

Summary:
After r345152 cached completions started adding namespaces after
nested name specifiers, e.g. in `some_name::^`

The CCC_Symbol indicates the completed item cannot be a namespace (it is
described as being "a type, a function or a variable" in the comments).

Therefore, 'nested specifier' completions should only be added from cache
when the context is CCC_SymbolOrNewName (which roughly seems to indicate
that a nested name specifier is allowed).

Fixes https://bugs.llvm.org/show_bug.cgi?id=42646

Reviewers: kadircet, sammccall

Reviewed By: kadircet, sammccall

Subscribers: arphaman, nik, sammccall, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64918

llvm-svn: 366448

clang/lib/Frontend/ASTUnit.cpp

@@ -435,7 +435,6 @@ void ASTUnit::CacheCodeCompletionResults() {
           | (1LL << CodeCompletionContext::CCC_UnionTag)
           | (1LL << CodeCompletionContext::CCC_ClassOrStructTag)
           | (1LL << CodeCompletionContext::CCC_Type)
-          | (1LL << CodeCompletionContext::CCC_Symbol)
           | (1LL << CodeCompletionContext::CCC_SymbolOrNewName)
           | (1LL << CodeCompletionContext::CCC_ParenthesizedExpression);
 

clang/test/Index/complete-qualified-cached.cpp

@@ -0,0 +1,22 @@
+namespace a_namespace {};
+class Class { static void foo(); };
+Class::
+// Completion for a_namespace should be available at the start of the line.
+// START-OF-LINE: a_namespace
+// START-OF-LINE: Class
+// -- Using cached completions.
+// RUN: CINDEXTEST_EDITING=1 c-index-test -code-completion-at=%s:3:1 %s \
+// RUN: | FileCheck --check-prefix=START-OF-LINE %s
+// -- Without cached completions.
+// RUN: c-index-test -code-completion-at=%s:3:1 %s \
+// RUN: | FileCheck --check-prefix=START-OF-LINE %s
+//
+//
+// ... and should not be available after 'Class::^'
+// AFTER-QUALIFIER: Class
+// -- Using cached completions.
+// RUN: CINDEXTEST_EDITING=1 c-index-test -code-completion-at=%s:3:8 %s \
+// RUN: | FileCheck --implicit-check-not=a_namespace --check-prefix=AFTER-QUALIFIER %s
+// -- Without cached completions.
+// RUN: c-index-test -code-completion-at=%s:3:8 %s \
+// RUN: | FileCheck --implicit-check-not=a_namespace --check-prefix=AFTER-QUALIFIER %s