Fix recording preamble's conditional stack in skipped PP branches.

Summary:
This fixes PR34547.
`Lexer::LexEndOfFile` handles recording of ConditionalStack for
preamble and reporting errors about unmatched conditionalal PP
directives.
However, SkipExcludedConditionalBlock contianed duplicated logic for
reporting errors and clearing ConditionalStack, but not for preamble
recording.

This fix removes error reporting logic from
`SkipExcludedConditionalBlock`, unmatched PP conditionals are now
reported inside `Lexer::LexEndOfFile`.

Reviewers: erikjv, klimek, bkramer

Reviewed By: erikjv

Subscribers: nik, cfe-commits

Differential Revision: https://reviews.llvm.org/D37700

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@313014 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Lex/PPDirectives.cpp

@@ -383,15 +383,8 @@ void Preprocessor::SkipExcludedConditionalBlock(const Token &HashToken,
 
     // If this is the end of the buffer, we have an error.
     if (Tok.is(tok::eof)) {
-      // Emit errors for each unterminated conditional on the stack, including
-      // the current one.
-      while (!CurPPLexer->ConditionalStack.empty()) {
-        if (CurLexer->getFileLoc() != CodeCompletionFileLoc)
-          Diag(CurPPLexer->ConditionalStack.back().IfLoc,
-               diag::err_pp_unterminated_conditional);
-        CurPPLexer->ConditionalStack.pop_back();
-      }
-
+      // We don't emit errors for unterminated conditionals here,
+      // Lexer::LexEndOfFile can do that propertly.
       // Just return and let the caller lex after this #include.
       break;
     }

test/Index/preamble-conditionals-inverted-with-error.cpp

@@ -0,0 +1,8 @@
+// RUN: env CINDEXTEST_EDITING=1 c-index-test -test-load-source-reparse 5 \
+// RUN:                                       local -std=c++14 %s 2>&1 \
+// RUN: | FileCheck %s
+#ifdef FOO_H
+
+void foo();
+
+// CHECK: preamble-conditionals-inverted-with-error.cpp:4:2: error: unterminated conditional directive

test/Index/preamble-conditionals-inverted.cpp

@@ -0,0 +1,8 @@
+// RUN: env CINDEXTEST_EDITING=1 c-index-test -test-load-source-reparse 5 \
+// RUN:                                       local -std=c++14 %s 2>&1 \
+// RUN: | FileCheck %s --implicit-check-not "error:"
+#ifdef FOO_H
+
+void foo();
+
+#endif