[clang] [Clang] Added explanation why a is trivial copyable evaluated to false. (PR #142341)

[Shamshura Egor via cfe-commits]

================
@@ -2083,6 +2086,97 @@ static void DiagnoseNonTriviallyRelocatableReason(Sema &SemaRef,
   SemaRef.Diag(D->getLocation(), diag::note_defined_here) << D;
 }
 
+static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
+                                               SourceLocation Loc,
+                                               const CXXRecordDecl *D) {
+  for (const CXXBaseSpecifier &B : D->bases()) {
+    assert(B.getType()->getAsCXXRecordDecl() && "invalid base?");
+    if (B.isVirtual())
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::VBase << B.getType()
+          << B.getSourceRange();
+    if (!B.getType().isTriviallyCopyableType(D->getASTContext())) {
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::NTCBase << B.getType()
+          << B.getSourceRange();
+    }
+  }
+  for (const FieldDecl *Field : D->fields()) {
+    if (!Field->getType().isTriviallyCopyableType(Field->getASTContext()))
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::NTCField << Field
+          << Field->getType() << Field->getSourceRange();
+  }
+  if (D->hasDeletedDestructor())
+    SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+        << diag::TraitNotSatisfiedReason::DeletedDtr << 0
+        << D->getDestructor()->getSourceRange();
+
+  if (D->isUnion()) {
+    auto DiagSPM = [&](CXXSpecialMemberKind K, bool Has) {
+      if (Has)
+        SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+            << diag::TraitNotSatisfiedReason::UnionWithUserDeclaredSMF << K;
+    };
+    DiagSPM(CXXSpecialMemberKind::CopyConstructor,
+            D->hasUserDeclaredCopyConstructor());
+    DiagSPM(CXXSpecialMemberKind::CopyAssignment,
+            D->hasUserDeclaredCopyAssignment());
+    DiagSPM(CXXSpecialMemberKind::MoveConstructor,
+            D->hasUserDeclaredMoveConstructor());
+    DiagSPM(CXXSpecialMemberKind::MoveAssignment,
+            D->hasUserDeclaredMoveAssignment());
+    return;
+  }
+
+  if (!D->hasSimpleMoveConstructor() && !D->hasSimpleCopyConstructor()) {
+    const auto *Decl = cast<CXXConstructorDecl>(
+        LookupSpecialMemberFromXValue(SemaRef, D, /*Assign=*/false));
+    if (Decl && Decl->isUserProvided())
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::UserProvidedCtr
+          << Decl->isMoveConstructor() << Decl->getSourceRange();
+  }
+  if (!D->hasSimpleMoveAssignment() && !D->hasSimpleCopyAssignment()) {
+    CXXMethodDecl *Decl =
+        LookupSpecialMemberFromXValue(SemaRef, D, /*Assign=*/true);
+    if (Decl && Decl->isUserProvided())
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::UserProvidedAssign
+          << Decl->isMoveAssignmentOperator() << Decl->getSourceRange();
+  }
----------------
egorshamshura wrote:

Fixed it, now I'm iterating over all special member functions

https://github.com/llvm/llvm-project/pull/142341