[Clang] omit parentheses in fold expressions with a single expansion

clang/docs/ReleaseNotes.rst

@@ -376,6 +376,8 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses when a ``requires`` expression has a local parameter of void type, aligning with the function parameter (#GH109831).
 
+- Clang now emits a diagnostic note at the class declaration when the method definition does not match any declaration (#GH110638).
+
 - Clang now omits warnings for extra parentheses in fold expressions with single expansion. (#GH101863)
 
 Improvements to Clang's time-trace

clang/lib/Sema/TreeTransform.h

@@ -15566,6 +15566,14 @@ TreeTransform<Derived>::TransformCXXFoldExpr(CXXFoldExpr *E) {
       return true;
   }
 
+  // When there's only one expansion, the parentheses can be safely eliminated
+  // to avoid any extra redundancy that may result in incorrect checks
+  // For example, transforming (((args == 0) || ...)) into (args == 0)
+  // allows the omission of parentheses while ensuring precise representation
+  // and avoiding warnings regarding redundant parentheses.
+  if (*NumExpansions == 1)
+    Pattern = Pattern->IgnoreParens();
+
   for (unsigned I = 0; I != *NumExpansions; ++I) {
     Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(
         getSema(), LeftFold ? I : *NumExpansions - I - 1);
@@ -15623,10 +15631,6 @@ TreeTransform<Derived>::TransformCXXFoldExpr(CXXFoldExpr *E) {
   if (Result.isUnset())
     return getDerived().RebuildEmptyCXXFoldExpr(E->getEllipsisLoc(),
                                                 E->getOperator());
-
-  if (*NumExpansions == 1)
-    Result = Result.get()->IgnoreParens();
-
   return Result;
 }
 

clang/test/SemaCXX/warn-assignment-condition.cpp

@@ -122,35 +122,34 @@ void test() {
 #undef EQ
 }
 
-void (*fn)();
-
-void test2() {
-    if ((fn == test2)) {} // expected-warning {{equality comparison with extraneous parentheses}} \
-                          // expected-note {{use '=' to turn this equality comparison into an assignment}} \
-                          // expected-note {{remove extraneous parentheses around the comparison to silence this warning}}
-    if ((test2 == fn)) {}
+namespace GH101863 {
+void t1(auto... args) {
+  if (((args == 0) or ...)) { }
 }
 
-namespace rdar9027658 {
-template <typename T>
-void f(T t) {
-    if ((t.g == 3)) { } // expected-warning {{equality comparison with extraneous parentheses}} \
-                         // expected-note {{use '=' to turn this equality comparison into an assignment}} \
-                         // expected-note {{remove extraneous parentheses around the comparison to silence this warning}}
+template <typename... Args>
+void t2(Args... args) {
+    if (((args == 0) or ...)) { }
 }
 
-struct S { int g; };
-void test() {
-  f(S()); // expected-note {{in instantiation}}
+void t3(auto... args) {
+  if ((... && (args == 0))) { }
 }
+
+void t4(auto... a, auto... b) {
+  if (((a == 0) or ...) && ((b == 0) or ...)) { }
 }
 
-namespace GH101863 {
-void foo(auto... args) {
-  if (((args == 0) or ...)) {} // ok
+void t5(auto... args) {
+  if ((((args == 0) or ...))) { }
 }
 
-void bar() {
-  foo(3);
+void test() {
+  t1(0, 1);
+  t2<>();
+  t3(1, 2, 3);
+  t3(0, 1);
+  t4(0, 1);
+  t5(0, 1);
 }
 }