improve loplugin rewriter double source modification detection

because my new rewriter easily generates overlapping rewriting.

Move the code from flatten and salcall up into the pluginhandler, and
drop the simpler detection logic.

Change-Id: I3da51ac510954a5d4276cee0924cc5dc1fc9a734
Reviewed-on: https://gerrit.libreoffice.org/49493
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/pluginhandler.hxx

@@ -54,10 +54,13 @@ public:
     DiagnosticBuilder report( DiagnosticsEngine::Level level, const char * plugin, StringRef message,
             CompilerInstance& compiler, SourceLocation loc = SourceLocation());
     bool ignoreLocation(SourceLocation loc);
-    bool addRemoval( SourceLocation loc );
     bool isDebugMode() const { return debugMode; }
     bool isLOOLMode() const { return !loolBasePath.empty(); }
     static bool isUnitTestMode();
+    // If we overlap with a previous area we modified, we cannot perform this change
+    // without corrupting the source
+    bool checkOverlap(SourceRange range);
+    bool addSourceModification(SourceRange range);
 private:
     void handleOption( const std::string& option );
     void createPlugins( std::set< std::string > rewriters );
@@ -67,12 +70,12 @@ private:
     StringRef const mainFileName;
     std::unordered_map<SourceLocation, bool> ignored_;
     Rewriter rewriter;
-    std::set< SourceLocation > removals;
     std::string scope;
     std::string warningsOnly;
     std::string loolBasePath;
     bool warningsAsErrors;
     bool debugMode = false;
+    std::vector<std::pair<char const*, char const*>> mvModifiedRanges;
 };
 
 /**