[clang-tidy] Untangle layering in ClangTidyDiagnosticConsumer somewhat. NFC

Summary:
Clang's hierarchy is CompilerInstance -> DiagnosticsEngine -> DiagnosticConsumer.
(Ownership is optional/shared, but this structure is fairly clear).

Currently ClangTidyDiagnosticConsumer *owns* the DiagnosticsEngine:
 - this inverts the hierarchy, which is confusing
 - this means ClangTidyDiagnosticConsumer() mutates the passed-in context, which
   is both surprising and limits flexibility
 - it's not possible to use a different DiagnosticsEngine with ClangTidy

This means a little bit more code in the places ClangTidy is used standalone,
but more flexibility in using ClangTidy with other diagnostics configurations.

Reviewers: hokein

Subscribers: xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D54033

llvm-svn: 346418

1 files changed, 1 insertions, 1 deletions

diff --git a/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp b/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
index da1e2255821..22448939e83 100644
--- a/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
+++ b/clang-tools-extra/clang-tidy/plugin/ClangTidyPlugin.cpp
@@ -35,7 +35,7 @@ public:
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &Compiler,
                                                  StringRef File) override {
     // Insert the current diagnostics engine.
-    Context->DiagEngine = &Compiler.getDiagnostics();
+    Context->setDiagnosticsEngine(&Compiler.getDiagnostics());
 
     // Create the AST consumer.
     ClangTidyASTConsumerFactory Factory(*Context);