From dba2b5c9314e1d127ee5200e739e6c8ca53a9831 Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan_svoboda@apple.com>
Date: Thu, 6 Jul 2023 19:27:48 -0700
Subject: [clang][modules] Skip submodule & framework re-definitions in module
 maps

Before D150478, there were situations when Clang avoided parsing a module map because it was likely to re-define an already defined module (either by a PCM or by previously-found module map). Since Clang no longer performs that check and does parse the extra module map (due to the FW/FW_Private issue described in D150478), this patch re-implements the same semantics by skipping the duplicate definition of the framework module while parsing the module map.

Depends on D150478.

Reviewed By: benlangmuir

Differential Revision: https://reviews.llvm.org/D150479
---
 clang/lib/Lex/ModuleMap.cpp | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'clang/lib/Lex/ModuleMap.cpp')

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index c97642e..4f713fe 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -2016,12 +2016,28 @@ void ModuleMapParser::parseModuleDecl() {
   Module *ShadowingModule = nullptr;
   if (Module *Existing = Map.lookupModuleQualified(ModuleName, ActiveModule)) {
     // We might see a (re)definition of a module that we already have a
-    // definition for in three cases:
+    // definition for in four cases:
     //  - If we loaded one definition from an AST file and we've just found a
     //    corresponding definition in a module map file, or
     bool LoadedFromASTFile = Existing->IsFromModuleFile;
     //  - If we previously inferred this module from different module map file.
     bool Inferred = Existing->IsInferred;
+    //  - If we're building a framework that vends a module map, we might've
+    //    previously seen the one in intermediate products and now the system
+    //    one.
+    // FIXME: If we're parsing module map file that looks like this:
+    //          framework module FW { ... }
+    //          module FW.Sub { ... }
+    //        We can't check the framework qualifier, since it's not attached to
+    //        the definition of Sub. Checking that qualifier on \c Existing is
+    //        not correct either, since we might've previously seen:
+    //          module FW { ... }
+    //          module FW.Sub { ... }
+    //        We should enforce consistency of redefinitions so that we can rely
+    //        that \c Existing is part of a framework iff the redefinition of FW
+    //        we have just skipped had it too. Once we do that, stop checking
+    //        the local framework qualifier and only rely on \c Existing.
+    bool PartOfFramework = Framework || Existing->isPartOfFramework();
     //  - If we're building a (preprocessed) module and we've just loaded the
     //    module map file from which it was created.
     bool ParsedAsMainInput =
@@ -2029,7 +2045,8 @@ void ModuleMapParser::parseModuleDecl() {
         Map.LangOpts.CurrentModule == ModuleName &&
         SourceMgr.getDecomposedLoc(ModuleNameLoc).first !=
             SourceMgr.getDecomposedLoc(Existing->DefinitionLoc).first;
-    if (!ActiveModule && (LoadedFromASTFile || Inferred || ParsedAsMainInput)) {
+    if (LoadedFromASTFile || Inferred || PartOfFramework || ParsedAsMainInput) {
+      ActiveModule = PreviousActiveModule;
       // Skip the module definition.
       skipUntil(MMToken::RBrace);
       if (Tok.is(MMToken::RBrace))
-- 
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