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

[Shamshura Egor via cfe-commits]

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@@ -2083,6 +2086,88 @@ 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();
+
+  for (const CXXMethodDecl *Method : D->methods()) {
+    if (Method->isIneligibleOrNotSelected() || Method->isTrivial() ||
+        !Method->isUserProvided()) {
+      continue;
+    }
+    auto SpecialMemberKind =
+        SemaRef.getDefaultedFunctionKind(Method).asSpecialMember();
+    switch (SpecialMemberKind) {
+    case CXXSpecialMemberKind::CopyConstructor:
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egorshamshura wrote:

Added tests for every single case

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