[ASTImport]CXXBoolLiteralExpr should be handled explicitly in statement comparation

[jcsxky]

Summary

In the comparation of return statement, return value(if it is CXXBoolLiteralExpr) should be handled explicitly, otherwise an incorrect result would be returned.

[donat.nagy]

Today we learned that truth is different from falsehood...

LGTM, nice catch!

[steakhal]

Make sure the commit message complies with the guidelines.

[jcsxky]

In D159479#4640607, @steakhal wrote:

Make sure the commit message complies with the guidelines.

Fix title and summary.

[jcsxky]

In D159479#4640590, @donat.nagy wrote:

Today we learned that truth is different from falsehood...

LGTM, nice catch!

Thanks for your quick review.

clang/lib/AST/ASTStructuralEquivalence.cpp

bool IsStmtEquivalent(const OverloadExpr *E1, const OverloadExpr *E2) {
     for (unsigned int ArgI = 0, ArgN = E1->getNumTemplateArgs(); ArgI < ArgN;
          ++ArgI)
       if (!IsStructurallyEquivalent(Context, Args1[ArgI], Args2[ArgI]))
         return false;
 
     return true;
   }
 
+  bool IsStmtEquivalent(const CXXBoolLiteralExpr *E1, const CXXBoolLiteralExpr *E2) {
+    return E1->getValue() == E2->getValue();
+  }
+
   /// End point of the traversal chain.
   bool TraverseStmt(const Stmt *S1, const Stmt *S2) { return true; }
 
   // Create traversal methods that traverse the class hierarchy and return
   // the accumulated result of the comparison. Each TraverseStmt overload
   // calls the TraverseStmt overload of the parent class. For example,
   // the TraverseStmt overload for 'BinaryOperator' calls the TraverseStmt
   // overload of 'Expr' which then calls the overload for 'Stmt'.

clang/unittests/AST/StructuralEquivalenceTest.cpp

TEST_F(StructuralEquivalenceCacheTest, SimpleNonEq) {
   EXPECT_FALSE(Ctx.IsEquivalent(X.first, X.second));
 
   EXPECT_FALSE(isInNonEqCache(findDeclPair<CXXRecordDecl>(
       TU, cxxRecordDecl(hasName("A"), unless(isImplicit())))));
   EXPECT_FALSE(isInNonEqCache(findDeclPair<CXXRecordDecl>(
       TU, cxxRecordDecl(hasName("B"), unless(isImplicit())))));
 }
 
+TEST_F(StructuralEquivalenceCacheTest, ReturnStmtNonEq) {
+  auto TU = makeTuDecls(
+      R"(
+      bool x(){ return true; }
+      )",
+      R"(
+      bool x(){ return false; }
+      )",
+      Lang_CXX03);
+
+  StructuralEquivalenceContext Ctx(
+      get<0>(TU)->getASTContext(), get<1>(TU)->getASTContext(),
+      NonEquivalentDecls, StructuralEquivalenceKind::Default, false, false);
+
+  auto X = findDeclPair<FunctionDecl>(TU, functionDecl(hasName("x")));
+  EXPECT_FALSE(Ctx.IsEquivalent(X.first->getBody(), X.second->getBody()));
+
+}
+
 TEST_F(StructuralEquivalenceCacheTest, SpecialNonEq) {
   auto TU = makeTuDecls(
       R"(
       class A {};
       class B { int i; };
       void x(A *);
       void y(A *);
       class C {