[clang] [clang][modules] Deserialize submodules lazily (PR #194968)

[Jan Svoboda via cfe-commits]

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@@ -222,6 +230,41 @@ struct ModuleAttributes {
         NoUndeclaredIncludes(false) {}
 };
 
+/// A reference to either a fully materialized Module object, or
+/// a yet-to-be-deserialized submodule in an AST file.
+class ModuleRef {
+  mutable Module *Existing = nullptr;
+  mutable ExternalSubmoduleSource *ExternalSource = nullptr;
+  mutable uint64_t SubmoduleID = 0;
+
+public:
+  ModuleRef() = default;
+  ModuleRef(Module *M) : Existing(M) {}
+  ModuleRef(ExternalSubmoduleSource *ExtSrc, uint64_t SubmoduleID)
+      : ExternalSource(ExtSrc), SubmoduleID(SubmoduleID) {}
+
+  Module *getExisting() const { return Existing; }
+  void setExisting(Module *E) { Existing = E; }
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jansvoboda11 wrote:

No, see https://github.com/llvm/llvm-project/pull/194968#discussion_r3197432750.

https://github.com/llvm/llvm-project/pull/194968