QDoc: Adapt clang/AST/QualTypeNames.h to breaking change

For compatibility reasons, QDoc carries a custom implementation of
`llvm-project.git/clang/lib/AST/QualTypeNames.cpp`. When QDoc is built
against Clang libraries from LLVM 21, QDoc fails to compile with five
separate errors:

  - no matching member function for call to
    'getTemplateSpecializationType'
    note: candidate function not viable: requires at most 3 arguments,
    but 4 were provided
  - enumeration value 'TypeSpecWithTemplate' not handled in switch
  - no matching function for call to 'Create'
    note: candidate function not viable: no known conversion from 'const
    Type *' to 'const IdentifierInfo *'/'const NamespaceDecl *'/
    'const NamespaceAliasDecl *' for 3rd argument
  - no member named 'getQualifier' in 'clang::MemberPointerType

The issues relate to several changes upstream, notably commit
14f7bd63b95d0f61a6f47119ac66398ca230559a (see [0]).

This change addresses the issues by adapting QDoc's custom
implementation. The required changes are wrapped in preprocessor
conditionals to ensure correct behavior with LLVM versions prior to 21
as well as 21 and above. Consequentially, the change also adds 21.1 as a
supported Clang version for QDoc.

There is one case of output regression; the index file entry for
`QMediaMetaData::asKeyValueRange<const QHash<Key, QVariant>>` from
qtmultimedia.git and its signature in a list generated in qtdoc.git now
partly desugars `Key` by adding template argument qualification.
However, as this specific function is documented with an fn-command that
overrides the declared return type using `auto`, this is considered
acceptable and a matter to be addressed elsewhere.

[0] - llvm/llvm-project#132401

Fixes: QTBUG-139407
Pick-to: 6.9 6.8
Change-Id: I2b1f88be27998eed6c03c9ebb068e21c6e9e3a17
Reviewed-by: Topi Reiniö <[email protected]>
Reviewed-by: Paul Wicking <[email protected]>
(cherry picked from commit 4abaf06)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: berolinux

src/qdoc/cmake/QDocConfiguration.cmake

@@ -8,6 +8,6 @@ set(QDOC_MINIMUM_CLANG_VERSION "17")
 
 # List of explicitly supported Clang versions for QDoc
 set(QDOC_SUPPORTED_CLANG_VERSIONS
-    "20.1" "19.1" "18.1" "17.0"
+    "21.1" "20.1" "19.1" "18.1" "17.0"
 )
 

src/qdoc/qdoc/src/qdoc/clang/AST/QualTypeNames.h

@@ -25,6 +25,7 @@ QT_WARNING_DISABLE_MSVC(4267)
 #include "clang/AST/DeclarationName.h"
 #include "clang/AST/GlobalDecl.h"
 #include "clang/AST/Mangle.h"
+#include "clang/Basic/Version.h"
 
 QT_WARNING_POP
 
@@ -160,9 +161,15 @@ static inline const Type *getFullyQualifiedTemplateType(const ASTContext &Ctx,
     // If a fully qualified arg is different from the unqualified arg,
     // allocate new type in the AST.
     if (MightHaveChanged) {
+#if CLANG_VERSION_MAJOR >= 21
+      QualType QT = Ctx.getTemplateSpecializationType(
+          TST->getTemplateName(), FQArgs, /*CanonicalArgs=*/{},
+          TST->getCanonicalTypeInternal());
+#else
       QualType QT = Ctx.getTemplateSpecializationType(
           TST->getTemplateName(), FQArgs,
           TST->getCanonicalTypeInternal());
+#endif
       // getTemplateSpecializationType returns a fully qualified
       // version of the specialization itself, so no need to qualify
       // it.
@@ -192,9 +199,15 @@ static inline const Type *getFullyQualifiedTemplateType(const ASTContext &Ctx,
       // allocate new type in the AST.
       if (MightHaveChanged) {
         TemplateName TN(TSTDecl->getSpecializedTemplate());
+#if CLANG_VERSION_MAJOR >= 21
+        QualType QT = Ctx.getTemplateSpecializationType(
+            TN, FQArgs, /*CanonicalArgs=*/{},
+            TSTRecord->getCanonicalTypeInternal());
+#else
         QualType QT = Ctx.getTemplateSpecializationType(
             TN, FQArgs,
             TSTRecord->getCanonicalTypeInternal());
+#endif
         // getTemplateSpecializationType returns a fully qualified
         // version of the specialization itself, so no need to qualify
         // it.
@@ -257,7 +270,10 @@ static inline NestedNameSpecifier *getFullyQualifiedNestedNameSpecifier(
           Ctx, Scope->getPrefix(), WithGlobalNsPrefix);
     case NestedNameSpecifier::Super:
     case NestedNameSpecifier::TypeSpec:
-    case NestedNameSpecifier::TypeSpecWithTemplate: {
+#if CLANG_VERSION_MAJOR < 21
+    case NestedNameSpecifier::TypeSpecWithTemplate:
+#endif
+    {
       const Type *Type = Scope->getAsType();
       // Find decl context.
       const TagDecl *TD = nullptr;
@@ -369,7 +385,10 @@ inline NestedNameSpecifier *createNestedNameSpecifier(const ASTContext &Ctx,
 
   return NestedNameSpecifier::Create(
       Ctx, createOuterNNS(Ctx, TD, FullyQualify, WithGlobalNsPrefix),
-      false /*No TemplateKeyword*/, TypePtr);
+#if CLANG_VERSION_MAJOR < 21
+      false /*No TemplateKeyword*/,
+#endif
+      TypePtr);
 }
 
 /// Return the fully qualified type, including fully-qualified
@@ -393,9 +412,13 @@ inline QualType getFullyQualifiedType(QualType QT, const ASTContext &Ctx,
     Qualifiers Quals = QT.getQualifiers();
     // Fully qualify the pointee and class types.
     QT = getFullyQualifiedType(QT->getPointeeType(), Ctx, WithGlobalNsPrefix);
+#if CLANG_VERSION_MAJOR >= 21
+    QT = Ctx.getMemberPointerType(QT, MPT->getQualifier(), MPT->getMostRecentCXXRecordDecl());
+#else
     QualType Class = getFullyQualifiedType(QualType(MPT->getClass(), 0), Ctx,
                                            WithGlobalNsPrefix);
     QT = Ctx.getMemberPointerType(QT, Class.getTypePtr());
+#endif
     // Add back the qualifiers.
     QT = Ctx.getQualifiedType(QT, Quals);
     return QT;