[Clang] Static member initializers are not immediate escalating context. (#66021)

Per CWG2760, default members initializers should be consider part the
body of constructors, which mean they are evaluated in an immediate
escalating context.

However, this does not apply to static members.

This patch produces some extraneous diagnostics, unfortunately we do not
have a good way to report an error back to the initializer and this is a
pre existing issue

Fixes #65985
Fixes #66562

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -287,6 +287,9 @@ Bug Fixes to C++ Support
   a non-template inner-class between the function and the class template.
   (`#65810 <https://github.com/llvm/llvm-project/issues/65810>`_)
 
+- Fix a crash when calling a non-constant immediate function
+  in the initializer of a static data member.
+  (`#65985 <https://github.com/llvm/llvm-project/issues/65985>_`).
 - Clang now properly converts static lambda call operator to function
   pointers on win32.
   (`#62594 <https://github.com/llvm/llvm-project/issues/62594>`_)

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3232,13 +3232,21 @@ ExprResult Parser::ParseCXXMemberInitializer(Decl *D, bool IsFunction,
   assert(Tok.isOneOf(tok::equal, tok::l_brace) &&
          "Data member initializer not starting with '=' or '{'");
 
+  bool IsFieldInitialization = isa_and_present<FieldDecl>(D);
+
   EnterExpressionEvaluationContext Context(
       Actions,
-      isa_and_present<FieldDecl>(D)
+      IsFieldInitialization
           ? Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed
           : Sema::ExpressionEvaluationContext::PotentiallyEvaluated,
       D);
-  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext = true;
+
+  // CWG2760
+  // Default member initializers used to initialize a base or member subobject
+  // [...] are considered to be part of the function body
+  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
+      IsFieldInitialization;
+
   if (TryConsumeToken(tok::equal, EqualLoc)) {
     if (Tok.is(tok::kw_delete)) {
       // In principle, an initializer of '= delete p;' is legal, but it will

clang/test/SemaCXX/cxx2a-consteval.cpp

@@ -1126,4 +1126,53 @@ int  test2() { return h{nullptr}; }
 // expected-note@-2 {{subobject 'g' is not initialized}}
 
 
+}
+
+namespace GH65985 {
+
+int consteval operator""_foo(unsigned long long V) {
+    return 0;
+}
+int consteval operator""_bar(unsigned long long V); // expected-note 3{{here}}
+
+int consteval f() {
+  return 0;
+}
+
+int consteval g();  // expected-note {{here}}
+
+
+struct C {
+    static const int a = 1_foo;
+    static constexpr int b = 1_foo;
+    static const int c = 1_bar; // expected-error {{call to consteval function 'GH65985::operator""_bar' is not a constant expression}} \
+                                // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}} \
+                                // expected-error {{in-class initializer for static data member is not a constant expression}}
+
+    // FIXME: remove duplicate diagnostics
+    static constexpr int d = 1_bar; // expected-error {{call to consteval function 'GH65985::operator""_bar' is not a constant expression}} \
+                                    // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}} \
+                                    // expected-error {{constexpr variable 'd' must be initialized by a constant expression}}  \
+                                    // expected-note {{undefined function 'operator""_bar' cannot be used in a constant expression}}
+
+    static const int e = f();
+    static const int f = g(); // expected-error {{call to consteval function 'GH65985::g' is not a constant expression}} \
+                              // expected-error {{in-class initializer for static data member is not a constant expression}} \
+                              // expected-note  {{undefined function 'g' cannot be used in a constant expression}}
+};
+
+}
+
+namespace GH66562 {
+
+namespace ns
+{
+    consteval int foo(int x) { return 1; } // expected-note {{declared here}}
+}
+
+template <class A>
+struct T {
+    static constexpr auto xx = ns::foo(A{}); // expected-error {{cannot take address of consteval function 'foo' outside of an immediate invocation}}
+};
+
 }

clang/test/SemaCXX/cxx2b-consteval-propagate.cpp

@@ -331,6 +331,21 @@ S s(0); // expected-note {{in the default initializer of 'j'}}
 
 }
 
+namespace GH65985 {
+consteval int invalid(); // expected-note 2{{declared here}}
+constexpr int escalating(auto) {
+    return invalid();
+    // expected-note@-1 {{'escalating<int>' is an immediate function because its body contains a call to a consteval function 'invalid' and that call is not a constant expression}}
+    // expected-note@-2 2{{undefined function 'invalid' cannot be used in a constant expression}}
+}
+struct S {
+    static constexpr int a = escalating(0); // expected-note 2{{in call to}}
+    // expected-error@-1 {{call to immediate function 'GH65985::escalating<int>' is not a constant expression}}
+    // expected-error@-2 {{constexpr variable 'a' must be initialized by a constant expression}}
+};
+
+}
+
 namespace GH66324 {
 
 consteval int allocate();  // expected-note  2{{declared here}}