[C++20][Modules] NFC Reworked handling of inline for functions defined in class (#109470)

Reworked handling of implicit inline marking for member and friend
function defined in class.
Now, we handle it in an additive manner, i.e. if such in-class functions
are inline implicitly by language rules,
we mark the as `setImplicitInline`, and perform no action otherwise.
As we never remove inline specifier, the implementation is orthogonal to
other sources of inline
(like `inline`, `constexpr`, e.t.c), and we do not need to handle them
specially.

Also included test for `constexpr`, `consteval` and global module cases.

Author: tomasz-kaminski-sonarsource

clang/lib/Sema/SemaDecl.cpp

@@ -9762,26 +9762,26 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   if (getLangOpts().CPlusPlus) {
     // The rules for implicit inlines changed in C++20 for methods and friends
     // with an in-class definition (when such a definition is not attached to
-    // the global module).  User-specified 'inline' overrides this (set when
-    // the function decl is created above).
+    // the global module). This does not affect declarations that are already
+    // inline (whether explicitly or implicitly by being declared constexpr,
+    // consteval, etc).
     // FIXME: We need a better way to separate C++ standard and clang modules.
     bool ImplicitInlineCXX20 = !getLangOpts().CPlusPlusModules ||
-                               NewFD->isConstexpr() || NewFD->isConsteval() ||
                                !NewFD->getOwningModule() ||
                                NewFD->isFromGlobalModule() ||
                                NewFD->getOwningModule()->isHeaderLikeModule();
     bool isInline = D.getDeclSpec().isInlineSpecified();
     bool isVirtual = D.getDeclSpec().isVirtualSpecified();
     bool hasExplicit = D.getDeclSpec().hasExplicitSpecifier();
     isFriend = D.getDeclSpec().isFriendSpecified();
-    if (isFriend && !isInline && D.isFunctionDefinition()) {
+    if (ImplicitInlineCXX20 && isFriend && D.isFunctionDefinition()) {
       // Pre-C++20 [class.friend]p5
       //   A function can be defined in a friend declaration of a
       //   class . . . . Such a function is implicitly inline.
       // Post C++20 [class.friend]p7
       //   Such a function is implicitly an inline function if it is attached
       //   to the global module.
-      NewFD->setImplicitlyInline(ImplicitInlineCXX20);
+      NewFD->setImplicitlyInline();
     }
 
     // If this is a method defined in an __interface, and is not a constructor
@@ -10083,15 +10083,15 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       break;
     }
 
-    if (isa<CXXMethodDecl>(NewFD) && DC == CurContext &&
-        D.isFunctionDefinition() && !isInline) {
+    if (ImplicitInlineCXX20 && isa<CXXMethodDecl>(NewFD) && DC == CurContext &&
+        D.isFunctionDefinition()) {
       // Pre C++20 [class.mfct]p2:
       //   A member function may be defined (8.4) in its class definition, in
       //   which case it is an inline member function (7.1.2)
       // Post C++20 [class.mfct]p1:
       //   If a member function is attached to the global module and is defined
       //   in its class definition, it is inline.
-      NewFD->setImplicitlyInline(ImplicitInlineCXX20);
+      NewFD->setImplicitlyInline();
     }
 
     if (!isFriend && SC != SC_None) {

clang/test/CXX/class/class.friend/p7-cxx20.cpp

@@ -46,14 +46,51 @@ module;
 export module M;
 
 class Z {
-  friend void z(){};
+  friend void z1(){};
 };
+
+class Inline {
+  friend inline void z2(){};
+};
+
+class Constexpr {
+  friend constexpr void z3(){};
+};
+
+class Consteval {
+  friend consteval void z4(){};
+};
+
+extern "C++" class GlobalModule {
+  friend void z5(){};
+};
+
 // CHECK-MOD: |-CXXRecordDecl {{.*}} <.{{/|\\\\?}}header.h:2:1, line:4:1> line:2:7 in M.<global> hidden class A definition
 // CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M.<global> hidden implicit class A
 // CHECK-MOD-NEXT: | `-FriendDecl {{.*}} <line:3:3, col:19> col:15 in M.<global>
 // CHECK-MOD-NEXT: |   `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:19> col:15 in M.<global> hidden friend_undeclared a 'void ()' implicit-inline
 
-// CHECK-MOD: `-CXXRecordDecl {{.*}} <module.cpp:6:1, line:8:1> line:6:7 in M hidden class Z{{( ReachableWhenImported)?}} definition
-// CHECK-MOD: |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Z{{( ReachableWhenImported)?}}
-// CHECK-MOD-NEXT: `-FriendDecl {{.*}} <line:7:3, col:19> col:15 in M{{( ReachableWhenImported)?}}
-// CHECK-MOD-NEXT: `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:19> col:15 in M hidden friend_undeclared z 'void ()'{{( ReachableWhenImported)?}}
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <module.cpp:6:1, line:8:1> line:6:7 in M hidden class Z{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Z{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-FriendDecl {{.*}} <line:7:3, col:20> col:15 in M{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: |   `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:20> col:15 in M hidden friend_undeclared z1 'void ()'{{( ReachableWhenImported)?}}
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:10:1, line:12:1> line:10:7 in M hidden class Inline{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Inline{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-FriendDecl {{.*}} <line:11:3, col:27> col:22 in M{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: |   `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:27> col:22 in M hidden friend_undeclared z2 'void ()'{{( ReachableWhenImported)?}} inline
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:14:1, line:16:1> line:14:7 in M hidden class Constexpr{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Constexpr{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-FriendDecl {{.*}} <line:15:3, col:30> col:25 in M{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: |   `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:30> col:25 in M hidden constexpr friend_undeclared z3 'void ()'{{( ReachableWhenImported)?}} implicit-inline
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:18:1, line:20:1> line:18:7 in M hidden class Consteval{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Consteval{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-FriendDecl {{.*}} <line:19:3, col:30> col:25 in M{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: |   `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:30> col:25 in M hidden consteval friend_undeclared z4 'void ()'{{( ReachableWhenImported)?}} implicit-inline
+
+// CHECK-MOD: `-CXXRecordDecl {{.*}} <col:14, line:24:1> line:22:20 in M.<implicit global> hidden class GlobalModule{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <col:14, col:20> col:20 in M.<implicit global> hidden implicit class GlobalModule{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: `-FriendDecl {{.*}} <line:23:3, col:20> col:15 in M.<implicit global>{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: `-FunctionDecl {{.*}} parent {{.*}} <col:3, col:20> col:15 in M.<implicit global> hidden friend_undeclared z5 'void ()'{{( ReachableWhenImported)?}} implicit-inline

clang/test/CXX/class/class.mfct/p1-cxx20.cpp

@@ -48,10 +48,42 @@ class Z {
   void z(){};
 };
 
+class Inline {
+  inline void z(){};
+};
+
+class Constexpr {
+  constexpr void z(){};
+};
+
+class Consteval {
+  consteval void z(){};
+};
+
+extern "C++" class GlobalModule {
+  void z(){};
+};
+
 // CHECK-MOD: |-CXXRecordDecl {{.*}} <.{{/|\\\\?}}header.h:2:1, line:4:1> line:2:7 in M.<global> hidden class A definition
 // CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M.<global> hidden implicit class A
 // CHECK-MOD-NEXT: | `-CXXMethodDecl {{.*}} <line:3:3, col:12> col:8 in M.<global> hidden a 'void ()' implicit-inline
 
-// CHECK-MOD: `-CXXRecordDecl {{.*}} <module.cpp:6:1, line:8:1> line:6:7 in M hidden class Z{{( ReachableWhenImported)?}} definition
-// CHECK-MOD: |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Z{{( ReachableWhenImported)?}}
-// CHECK-MOD-NEXT: `-CXXMethodDecl {{.*}} <line:7:3, col:12> col:8 in M hidden z 'void ()'{{( ReachableWhenImported)?}}
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <module.cpp:6:1, line:8:1> line:6:7 in M hidden class Z{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Z{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-CXXMethodDecl {{.*}} <line:7:3, col:12> col:8 in M hidden z 'void ()'{{( ReachableWhenImported)?}}
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:10:1, line:12:1> line:10:7 in M hidden class Inline{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Inline{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-CXXMethodDecl {{.*}} <line:11:3, col:19> col:15 in M hidden z 'void ()'{{( ReachableWhenImported)?}} inline
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:14:1, line:16:1> line:14:7 in M hidden class Constexpr{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Constexpr{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-CXXMethodDecl {{.*}} <line:15:3, col:22> col:18 in M hidden constexpr z 'void ()'{{( ReachableWhenImported)?}} implicit-inline
+
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <line:18:1, line:20:1> line:18:7 in M hidden class Consteval{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: | |-CXXRecordDecl {{.*}} <col:1, col:7> col:7 in M hidden implicit class Consteval{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: | `-CXXMethodDecl {{.*}} <line:19:3, col:22> col:18 in M hidden consteval z 'void ()'{{( ReachableWhenImported)?}} implicit-inline
+
+// CHECK-MOD: `-CXXRecordDecl {{.*}} <col:14, line:24:1> line:22:20 in M.<implicit global> hidden class GlobalModule{{( ReachableWhenImported)?}} definition
+// CHECK-MOD: |-CXXRecordDecl {{.*}} <col:14, col:20> col:20 in M.<implicit global> hidden implicit class GlobalModule{{( ReachableWhenImported)?}}
+// CHECK-MOD-NEXT: `-CXXMethodDecl {{.*}} <line:23:3, col:12> col:8 in M.<implicit global> hidden z 'void ()'{{( ReachableWhenImported)?}} implicit-inline