[clang] [Modules] No transitive source location change (PR #86912)

[Jan Svoboda via cfe-commits]

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@@ -942,6 +942,12 @@ class ASTReader
   /// Sema tracks these to emit deferred diags.
   llvm::SmallSetVector<serialization::DeclID, 4> DeclsToCheckForDeferredDiags;
 
+  /// The module files imported by different module files. Indirectly imported
+  /// module files are included too. The information comes from
+  /// ReadModuleOffsetMap(ModuleFile&).
+  mutable llvm::DenseMap<ModuleFile *, llvm::SmallVector<ModuleFile *>>
+      ImportedModuleFiles;
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jansvoboda11 wrote:

Why does this live in `ASTReader`? If we moved it to `ModuleFile`, we could remove `mutable` and the map lookups.

https://github.com/llvm/llvm-project/pull/86912