[Clang] Static member initializers are not immediate escalating context.

Per CWG2760, default members initializers should be consider
part the body of consstructors, 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 preexisting issue

Fixes #65985

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -281,6 +281,10 @@ 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>_`).
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.

clang/lib/Parse/ParseDeclCXX.cpp

@@ -3230,13 +3230,21 @@ 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/cxx2b-consteval-propagate.cpp

@@ -330,3 +330,26 @@ struct S {
 S s(0); // expected-note {{in the default initializer of 'j'}}
 
 }
+
+namespace GH65985 {
+
+int consteval operator""_foo(unsigned long long V) {
+    return 0;
+}
+int consteval operator""_bar(unsigned long long V); // expected-note 3{{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}}
+};
+
+}