[clang-tools-extra] [clang-include-cleaner] Add --mapping-file support for IWYU .imp mapping files. (PR #195987)

[Kim Gräsman via cfe-commits]

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@@ -254,6 +255,28 @@ llvm::SmallVector<Header> headersForSymbol(const Symbol &S,
     for (auto &Loc : locateSymbol(S, PP.getLangOpts()))
       Headers.append(applyHints(findHeaders(Loc, SM, PI), Loc.Hint));
   }
+
+  // Apply external symbol mappings from mapping files.  We check both the
+  // simple (unqualified) name and, for declarations, the fully-qualified name.
+  if (PI) {
+    auto AddSymbolMapping = [&](llvm::StringRef Name) {
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kimgr wrote:

Just a heads-up that IWYU now supports function overloads and template specializations as well:

* https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/IWYUMappings.md#overloaded-functions
* https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/IWYUMappings.md#overloaded-functions

So if you're planning to consume IWYU .imp files, you may see records with more type decorations.

https://github.com/llvm/llvm-project/pull/195987