[Clang][Sema] Earlier type checking for builtin unary operators (#90500)

Currently, clang postpones all semantic analysis of unary operators with operands of pointer/pointer to member/array/function type until instantiation whenever that type is dependent (e.g. `T*` where `T` is a type template parameter). Consequently, the uninstantiated AST nodes all have the type `ASTContext::DependentTy` (which, for the purposes of #90152, is undesirable as that type may be the current instantiation! (e.g. `*this`)) This patch moves the point at which we perform semantic analysis for such expression to be prior to instantiation.
llvm · May 14, 2024 · 8019cbb · 8019cbb
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diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -55,6 +55,9 @@ C++ Specific Potentially Breaking Changes
 
 - Clang now rejects pointer to member from parenthesized expression in unevaluated context such as ``decltype(&(foo::bar))``. (#GH40906).
 
+- Clang now performs semantic analysis for unary operators with dependent operands
+  that are known to be of non-class non-enumeration type prior to instantiation.
+
 ABI Changes in This Version
 ---------------------------
 - Fixed Microsoft name mangling of implicitly defined variables used for thread

diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
@@ -8044,7 +8044,10 @@ inline bool Type::isUndeducedType() const {
 /// Determines whether this is a type for which one can define
 /// an overloaded operator.
 inline bool Type::isOverloadableType() const {
-  return isDependentType() || isRecordType() || isEnumeralType();
+  if (!CanonicalType->isDependentType())
+    return isRecordType() || isEnumeralType();
+  return !isArrayType() && !isFunctionType() && !isAnyPointerType() &&
+         !isMemberPointerType();
 }
 
 /// Determines whether this type is written as a typedef-name.

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
diff --git a/clang/test/AST/ast-dump-expr-json.cpp b/clang/test/AST/ast-dump-expr-json.cpp
@@ -4261,9 +4261,9 @@ void TestNonADLCall3() {
 // CHECK-NEXT:                     }
 // CHECK-NEXT:                    },
 // CHECK-NEXT:                    "type": {
-// CHECK-NEXT:                     "qualType": "<dependent type>"
+// CHECK-NEXT:                     "qualType": "V"
 // CHECK-NEXT:                    },
-// CHECK-NEXT:                    "valueCategory": "prvalue",
+// CHECK-NEXT:                    "valueCategory": "lvalue",
 // CHECK-NEXT:                    "isPostfix": false,
 // CHECK-NEXT:                    "opcode": "*",
 // CHECK-NEXT:                    "canOverflow": false,

diff --git a/clang/test/AST/ast-dump-expr.cpp b/clang/test/AST/ast-dump-expr.cpp
@@ -282,7 +282,7 @@ void PrimaryExpressions(Ts... a) {
       // CHECK-NEXT: CompoundStmt
       // CHECK-NEXT: FieldDecl 0x{{[^ ]*}} <col:8> col:8 implicit 'V'
       // CHECK-NEXT: ParenListExpr 0x{{[^ ]*}} <col:8> 'NULL TYPE'
-      // CHECK-NEXT: UnaryOperator 0x{{[^ ]*}} <col:8> '<dependent type>' prefix '*' cannot overflow
+      // CHECK-NEXT: UnaryOperator 0x{{[^ ]*}} <col:8> 'V' lvalue prefix '*' cannot overflow
       // CHECK-NEXT: CXXThisExpr 0x{{[^ ]*}} <col:8> 'V *' this
     }
   };

diff --git a/clang/test/AST/ast-dump-lambda.cpp b/clang/test/AST/ast-dump-lambda.cpp
@@ -81,7 +81,7 @@ template <typename... Ts> void test(Ts... a) {
 // CHECK-NEXT:    |         | | `-CompoundStmt {{.*}} <col:15, col:16>
 // CHECK-NEXT:    |         | `-FieldDecl {{.*}} <col:8> col:8{{( imported)?}} implicit 'V'
 // CHECK-NEXT:    |         |-ParenListExpr {{.*}} <col:8> 'NULL TYPE'
-// CHECK-NEXT:    |         | `-UnaryOperator {{.*}} <col:8> '<dependent type>' prefix '*' cannot overflow
+// CHECK-NEXT:    |         | `-UnaryOperator {{.*}} <col:8> 'V' lvalue prefix '*' cannot overflow
 // CHECK-NEXT:    |         |   `-CXXThisExpr {{.*}} <col:8> 'V *' this
 // CHECK-NEXT:    |         `-CompoundStmt {{.*}} <col:15, col:16>
 // CHECK-NEXT:    |-DeclStmt {{.*}} <line:22:3, col:11>

diff --git a/clang/test/CXX/expr/expr.unary/expr.unary.general/p1.cpp b/clang/test/CXX/expr/expr.unary/expr.unary.general/p1.cpp
@@ -0,0 +1,65 @@
+// RUN: %clang_cc1 -Wno-unused -fsyntax-only %s -verify
+
+struct A {
+  void operator*();
+  void operator+();
+  void operator-();
+  void operator!();
+  void operator~();
+  void operator&();
+  void operator++();
+  void operator--();
+};
+
+struct B { };
+
+template<typename T, typename U>
+void dependent(T t, T* pt, T U::* mpt, T(&ft)(), T(&at)[4]) {
+  *t;
+  +t;
+  -t;
+  !t;
+  ~t;
+  &t;
+  ++t;
+  --t;
+
+  *pt;
+  +pt;
+  -pt; // expected-error {{invalid argument type 'T *' to unary expression}}
+  !pt;
+  ~pt; // expected-error {{invalid argument type 'T *' to unary expression}}
+  &pt;
+  ++pt;
+  --pt;
+
+  *mpt; // expected-error {{indirection requires pointer operand ('T U::*' invalid)}}
+  +mpt; // expected-error {{invalid argument type 'T U::*' to unary expression}}
+  -mpt; // expected-error {{invalid argument type 'T U::*' to unary expression}}
+  !mpt;
+  ~mpt; // expected-error {{invalid argument type 'T U::*' to unary expression}}
+  &mpt;
+  ++mpt; // expected-error {{cannot increment value of type 'T U::*'}}
+  --mpt; // expected-error {{cannot decrement value of type 'T U::*'}}
+
+  *ft;
+  +ft;
+  -ft; // expected-error {{invalid argument type 'T (*)()' to unary expression}}
+  !ft;
+  ~ft; // expected-error {{invalid argument type 'T (*)()' to unary expression}}
+  &ft;
+  ++ft; // expected-error {{cannot increment value of type 'T ()'}}
+  --ft; // expected-error {{cannot decrement value of type 'T ()'}}
+
+  *at;
+  +at;
+  -at; // expected-error {{invalid argument type 'T *' to unary expression}}
+  !at;
+  ~at; // expected-error {{invalid argument type 'T *' to unary expression}}
+  &at;
+  ++at; // expected-error {{cannot increment value of type 'T[4]'}}
+  --at; // expected-error {{cannot decrement value of type 'T[4]'}}
+}
+
+// Make sure we only emit diagnostics once.
+template void dependent(A t, A* pt, A B::* mpt, A(&ft)(), A(&at)[4]);
diff --git a/clang/test/CXX/over/over.built/ast.cpp b/clang/test/CXX/over/over.built/ast.cpp
@@ -1,41 +1,139 @@
-// RUN: %clang_cc1 -std=c++17 -ast-dump %s -ast-dump-filter Test | FileCheck %s
+// RUN: %clang_cc1 -std=c++17 -Wno-unused -ast-dump %s -ast-dump-filter Test | FileCheck %s
 
-struct A{};
+namespace Test {
+  template<typename T, typename U>
+  void Unary(T t, T* pt, T U::* mpt, T(&ft)(), T(&at)[4]) {
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' lvalue prefix '*' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    *t;
 
-template <typename T, typename U>
-auto Test(T* pt, U* pu) {
-  // CHECK: UnaryOperator {{.*}} '<dependent type>' lvalue prefix '*'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  (void)*pt;
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '+' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    +t;
 
-  // CHECK: UnaryOperator {{.*}} '<dependent type>' lvalue prefix '++'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  (void)(++pt);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '-' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    -t;
 
-  // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '+'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  (void)(+pt);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '!' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    !t;
 
-  // CHECK: BinaryOperator {{.*}} '<dependent type>' '+'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 3
-  (void)(pt + 3);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '~' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    ~t;
 
-  // CHECK: BinaryOperator {{.*}} '<dependent type>' '-'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  (void)(pt - pt);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '&' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    &t;
 
-  // CHECK: BinaryOperator {{.*}} '<dependent type>' '-'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'U *' lvalue ParmVar {{.*}} 'pu' 'U *'
-  (void)(pt - pu);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' lvalue prefix '++' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    ++t;
 
-  // CHECK: BinaryOperator {{.*}} '<dependent type>' '=='
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
-  // CHECK-NEXT: DeclRefExpr {{.*}} 'U *' lvalue ParmVar {{.*}} 'pu' 'U *'
-  (void)(pt == pu);
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' lvalue prefix '--' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T' lvalue ParmVar {{.*}} 't' 'T'
+    --t;
 
-}
+    // CHECK: UnaryOperator {{.*}} 'T' lvalue prefix '*' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <LValueToRValue>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    *pt;
 
+    // CHECK: UnaryOperator {{.*}} 'T *' prefix '+' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <LValueToRValue>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    +pt;
 
+    // CHECK: UnaryOperator {{.*}} 'bool' prefix '!' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'bool' <PointerToBoolean>
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <LValueToRValue>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    !pt;
+
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '&' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    &pt;
+
+    // CHECK: UnaryOperator {{.*}} 'T *' lvalue prefix '++' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    ++pt;
+
+    // CHECK: UnaryOperator {{.*}} 'T *' lvalue prefix '--' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    --pt;
+
+    // CHECK: UnaryOperator {{.*}} 'bool' prefix '!' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'bool' <MemberPointerToBoolean>
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T U::*' <LValueToRValue>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T U::*' lvalue ParmVar {{.*}} 'mpt' 'T U::*'
+    !mpt;
+
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '&' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T U::*' lvalue ParmVar {{.*}} 'mpt' 'T U::*'
+    &mpt;
+
+    // CHECK: UnaryOperator {{.*}} 'T ()' lvalue prefix '*' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T (*)()' <FunctionToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T ()' lvalue ParmVar {{.*}} 'ft' 'T (&)()'
+    *ft;
+
+    // CHECK: UnaryOperator {{.*}} 'T (*)()' prefix '+' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T (*)()' <FunctionToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T ()' lvalue ParmVar {{.*}} 'ft' 'T (&)()'
+    +ft;
+
+    // CHECK: UnaryOperator {{.*}} 'bool' prefix '!' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'bool' <PointerToBoolean>
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T (*)()' <FunctionToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T ()' lvalue ParmVar {{.*}} 'ft' 'T (&)()'
+    !ft;
+
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '&' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T ()' lvalue ParmVar {{.*}} 'ft' 'T (&)()'
+    &ft;
+
+    // CHECK: UnaryOperator {{.*}} 'T' lvalue prefix '*' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <ArrayToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T[4]' lvalue ParmVar {{.*}} 'at' 'T (&)[4]'
+    *at;
+
+    // CHECK: UnaryOperator {{.*}} 'T *' prefix '+' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <ArrayToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T[4]' lvalue ParmVar {{.*}} 'at' 'T (&)[4]'
+    +at;
+
+    // CHECK: UnaryOperator {{.*}} 'bool' prefix '!' cannot overflow
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'bool' <PointerToBoolean>
+    // CHECK-NEXT: ImplicitCastExpr {{.*}} 'T *' <ArrayToPointerDecay>
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T[4]' lvalue ParmVar {{.*}} 'at' 'T (&)[4]'
+    !at;
+
+    // CHECK: UnaryOperator {{.*}} '<dependent type>' prefix '&' cannot overflow
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T[4]' lvalue ParmVar {{.*}} 'at' 'T (&)[4]'
+    &at;
+  }
+
+  template<typename T, typename U>
+  void Binary(T* pt, U* pu) {
+    // CHECK: BinaryOperator {{.*}} '<dependent type>' '+'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    // CHECK-NEXT: IntegerLiteral {{.*}} 'int' 3
+    pt + 3;
+
+    // CHECK: BinaryOperator {{.*}} '<dependent type>' '-'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    pt - pt;
+
+    // CHECK: BinaryOperator {{.*}} '<dependent type>' '-'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'U *' lvalue ParmVar {{.*}} 'pu' 'U *'
+    pt - pu;
+
+    // CHECK: BinaryOperator {{.*}} '<dependent type>' '=='
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'T *' lvalue ParmVar {{.*}} 'pt' 'T *'
+    // CHECK-NEXT: DeclRefExpr {{.*}} 'U *' lvalue ParmVar {{.*}} 'pu' 'U *'
+    pt == pu;
+  }
+} // namespace Test
diff --git a/clang/test/CXX/over/over.built/p10.cpp b/clang/test/CXX/over/over.built/p10.cpp
@@ -15,6 +15,6 @@ void f(int i, float f, bool b, char c, int* pi, A* pa, T* pt) {
 
   (void)-pi; // expected-error {{invalid argument type}}
   (void)-pa; // expected-error {{invalid argument type}}
-  (void)-pt; // FIXME: we should be able to give an error here.
+  (void)-pt; // expected-error {{invalid argument type}}
 }
 
diff --git a/clang/test/CXX/over/over.built/p11.cpp b/clang/test/CXX/over/over.built/p11.cpp
@@ -7,6 +7,6 @@ void f(int i, float f, bool b, char c, int* pi, T* pt) {
   (void)~b;
   (void)~c;
   (void)~pi; // expected-error {{invalid argument type}}
-  (void)~pt; // FIXME: we should be able to give an error here.
+  (void)~pt; // expected-error {{invalid argument type}}
 }
 
diff --git a/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p4.cpp b/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p4.cpp
@@ -357,17 +357,14 @@ namespace N0 {
       a->A::f4(); // expected-error{{no member named 'f4' in 'N0::A'}}
       a->B::A::f4(); // expected-error{{no member named 'f4' in 'N0::A'}}
 
-      // FIXME: An overloaded unary 'operator*' is built for these
-      // even though the operand is a pointer (to a dependent type).
-      // Type::isOverloadableType should return false for such cases.
-      (*this).x4;
-      (*this).B::x4;
-      (*this).A::x4;
-      (*this).B::A::x4;
-      (*this).f4();
-      (*this).B::f4();
-      (*this).A::f4();
-      (*this).B::A::f4();
+      (*this).x4; // expected-error{{no member named 'x4' in 'B<T>'}}
+      (*this).B::x4; // expected-error{{no member named 'x4' in 'B<T>'}}
+      (*this).A::x4; // expected-error{{no member named 'x4' in 'N0::A'}}
+      (*this).B::A::x4; // expected-error{{no member named 'x4' in 'N0::A'}}
+      (*this).f4(); // expected-error{{no member named 'f4' in 'B<T>'}}
+      (*this).B::f4(); // expected-error{{no member named 'f4' in 'B<T>'}}
+      (*this).A::f4(); // expected-error{{no member named 'f4' in 'N0::A'}}
+      (*this).B::A::f4(); // expected-error{{no member named 'f4' in 'N0::A'}}
 
       b.x4; // expected-error{{no member named 'x4' in 'B<T>'}}
       b.B::x4; // expected-error{{no member named 'x4' in 'B<T>'}}
@@ -399,15 +396,13 @@ namespace N1 {
       f<0>();
       this->f<0>();
       a->f<0>();
-      // FIXME: This should not require 'template'!
-      (*this).f<0>(); // expected-error{{missing 'template' keyword prior to dependent template name 'f'}}
+      (*this).f<0>();
       b.f<0>();
 
       x.f<0>();
       this->x.f<0>();
       a->x.f<0>();
-      // FIXME: This should not require 'template'!
-      (*this).x.f<0>(); // expected-error{{missing 'template' keyword prior to dependent template name 'f'}}
+      (*this).x.f<0>();
       b.x.f<0>();
 
       // FIXME: None of these should require 'template'!

diff --git a/clang/test/Frontend/noderef_templates.cpp b/clang/test/Frontend/noderef_templates.cpp
@@ -3,8 +3,8 @@
 #define NODEREF __attribute__((noderef))
 
 template <typename T>
-int func(T NODEREF *a) { // expected-note 2 {{a declared here}}
-  return *a + 1;         // expected-warning 2 {{dereferencing a; was declared with a 'noderef' type}}
+int func(T NODEREF *a) { // expected-note 3 {{a declared here}}
+  return *a + 1;         // expected-warning 3 {{dereferencing a; was declared with a 'noderef' type}}
 }
 
 void func() {

diff --git a/clang/test/SemaCXX/cxx2b-deducing-this.cpp b/clang/test/SemaCXX/cxx2b-deducing-this.cpp
@@ -19,7 +19,7 @@ struct S {
     // new and delete are implicitly static
     void *operator new(this unsigned long); // expected-error{{an explicit object parameter cannot appear in a static function}}
     void operator delete(this void*); // expected-error{{an explicit object parameter cannot appear in a static function}}
-    
+
     void g(this auto) const; // expected-error{{explicit object member function cannot have 'const' qualifier}}
     void h(this auto) &; // expected-error{{explicit object member function cannot have '&' qualifier}}
     void i(this auto) &&; // expected-error{{explicit object member function cannot have '&&' qualifier}}
@@ -198,9 +198,7 @@ void func(int i) {
 void TestMutationInLambda() {
     [i = 0](this auto &&){ i++; }();
     [i = 0](this auto){ i++; }();
-    [i = 0](this const auto&){ i++; }();
-    // expected-error@-1 {{cannot assign to a variable captured by copy in a non-mutable lambda}}
-    // expected-note@-2 {{in instantiation of}}
+    [i = 0](this const auto&){ i++; }(); // expected-error {{cannot assign to a variable captured by copy in a non-mutable lambda}}
 
     int x;
     const auto l1 = [x](this auto&) { x = 42; }; // expected-error {{cannot assign to a variable captured by copy in a non-mutable lambda}}