Fix range-loop-analysis checks for trivial copyability

[fanfuqiang]

Summary

fix https://bugs.llvm.org/show_bug.cgi?id=48011

[• Quuxplusone]

clang/test/SemaCXX/warn-range-loop-analysis.cpp

35

I recommend adding ID1(ID1 const&) = default; here. My understanding is that C++20 has deprecated auto-generating a defaulted copy constructor for a class with a user-defined copy-assignment operator. See -Wdeprecated-copy.

478

Isn't the point of https://bugs.llvm.org/show_bug.cgi?id=48011 that there should be no warning for for (ID1 x : C) {}? There is already no warning for the const& case tested here.

[fanfuqiang]

This comment was removed by fanfuqiang.

[fanfuqiang]

update testcase take advise of reviewers.
fix conflict testcase fail, less warnning only for hasNonTrivialCopyConstructor .

[gandhi21299]

I tried to implement a fix by using the hasCopyAssignmentWithConstParam() method (instead of hasNonTrivialCopyConstructor()), the test trivially-copyable.cc fails due to a missing warning.

[gandhi21299]

LGTM, thanks for the bug fix!

[• Quuxplusone]

What ever happened to this patch? @fanfuqiang, are you still around to rebase this? Do you need someone to commit it for you?
(Not that I'm saying I think it's perfect as is — I haven't looked and don't know the code that well — but just wondering what kept this from being landed a year ago.)

The bug it fixes is now https://github.com/llvm/llvm-project/issues/47355

[gandhi21299]

@Quuxplusone I can commit this patch on behalf of @fanfuqiang.

[gandhi21299]

Perhaps, a description could be added to this patch before committing.

clang/lib/Sema/SemaStmt.cpp

   // diagnostic for these instances. 64 bytes is a common size of a cache line.
   // (The function `getTypeSize` returns the size in bits.)
   ASTContext &Ctx = SemaRef.Context;
+  const CXXRecordDecl *ClassDecl = nullptr;
+  if (const auto *RT = VariableType->getAs<RecordType>()) {
+    ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl());
+  }
   if (Ctx.getTypeSize(VariableType) <= 64 * 8 &&
       (VariableType.isTriviallyCopyableType(Ctx) ||
+       // Fix https://bugs.llvm.org/show_bug.cgi?id=48011
+       (ClassDecl && !ClassDecl->hasNonTrivialCopyConstructor()) ||
        hasTrivialABIAttr(VariableType)))
     return;
 

clang/test/SemaCXX/warn-range-loop-analysis-trivially-copyable.cpp

     int b;
   };
 
-  // expected-warning@+3 {{loop variable 'r' creates a copy from type 'const Record'}}
-  // expected-note@+2 {{use reference type 'const Record &' to prevent copying}}
   Record records[8];
   for (const auto r : records)
     (void)r;

clang/test/SemaCXX/warn-range-loop-analysis.cpp

   operator int();
 };
 
+struct ID1 {
+  // Small trivally copy constructor, but no trivally copy assignment 
+  // operator.
+  ID1(ID1 const&) = default;
+  ID1& operator=(ID1 const& other) { return *this; }
+};
+
 // Testing notes:
 // test0 checks that the full text of the warnings and notes is correct.  The
 //   rest of the tests checks a smaller portion of the text.

   // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:17-[[@LINE-3]]:18}:" "
 }
 
+void test11() {
+  Container<ID1> C;
+
+  for (const ID1 x : C) {}
+  // No warning
+}
+
+
 template <class T>
 void test_template_function() {
   // In a template instantiation the diagnostics should not be emitted for