Allowing link decls in explicit submodules.

Author: qiongsiwu

clang/lib/Lex/ModuleMapFile.cpp

@@ -119,7 +119,7 @@ struct ModuleMapFileParser {
   std::optional<UmbrellaDirDecl>
   parseUmbrellaDirDecl(SourceLocation UmbrellaLoc);
   std::optional<LinkDecl>
-  parseLinkDecl(llvm::StringMap<SourceLocation> &SeenLinkDecl, bool TopLevel);
+  parseLinkDecl(llvm::StringMap<SourceLocation> &SeenLinkDecl, bool Allowed);
 
   SourceLocation consumeToken();
   void skipUntil(MMToken::TokenKind K);
@@ -407,7 +407,9 @@ std::optional<ModuleDecl> ModuleMapFileParser::parseModuleDecl(bool TopLevel) {
       break;
 
     case MMToken::LinkKeyword:
-      SubDecl = parseLinkDecl(SeenLinkDecl, TopLevel);
+      // Link decls are only allowed in top level modules or explicit
+      // submodules.
+      SubDecl = parseLinkDecl(SeenLinkDecl, TopLevel || MDecl.Explicit);
       break;
 
     default:
@@ -825,7 +827,7 @@ ModuleMapFileParser::parseUmbrellaDirDecl(clang::SourceLocation UmbrellaLoc) {
 ///   module-declaration:
 ///     'link' 'framework'[opt] string-literal
 std::optional<LinkDecl> ModuleMapFileParser::parseLinkDecl(
-    llvm::StringMap<SourceLocation> &SeenLinkDecl, bool TopLevel) {
+    llvm::StringMap<SourceLocation> &SeenLinkDecl, bool Allowed) {
   assert(Tok.is(MMToken::LinkKeyword));
   LinkDecl LD;
   LD.Location = consumeToken();
@@ -853,7 +855,7 @@ std::optional<LinkDecl> ModuleMapFileParser::parseLinkDecl(
 
   // Make sure we eat all the tokens when we report the errors so parsing
   // can continue.
-  if (!TopLevel) {
+  if (!Allowed) {
     Diags.Report(LD.Location, diag::err_mmap_submodule_link_decl);
     HadError = true;
     return std::nullopt;

clang/test/ClangScanDeps/link-libraries-diag-dup.c

@@ -11,6 +11,11 @@ module A {
     link "libraryB"
   }
 
+  explicit module D {
+    header "D.h"
+    link "libraryD"
+  }
+
   link "libraryA"
   link "libraryA"
 }
@@ -26,9 +31,12 @@ module C {
 // empty
 //--- C.h
 // empty
+//--- D.h
+// empty
 //--- TU.c
 #include "A.h"
 #include "C.h"
+#include "D.h"
 
 //--- cdb.json.template
 [{
@@ -41,7 +49,9 @@ module C {
 // RUN: not clang-scan-deps -compilation-database %t/cdb.json -format \
 // RUN:   experimental-full 2>&1 | FileCheck %s
 
-// CHECK:      module.modulemap:6:5: error: link decl is not allowed in submodules
-// CHECK-NEXT: module.modulemap:10:3: error: redeclaration of link library 'libraryA'
-// CHECK-NEXT: module.modulemap:9:3: note: previously declared here
-// CHECK-NOT: module.modulemap:15:3: error: redeclaration of link library 'libraryA'
+// Note that module D does not report an error because it is explicit.
+// Therefore we can use CHECK-NEXT for the redeclaration error on line 15.
+// CHECK:      module.modulemap:6:5: error: link declaration is not allowed in submodules
+// CHECK-NEXT: module.modulemap:15:3: error: redeclaration of link library 'libraryA'
+// CHECK-NEXT: module.modulemap:14:3: note: previously declared here
+// CHECK-NOT:  module.modulemap:20:3: error: redeclaration of link library 'libraryA'