[clang][bytecode] Fix const-in-mutable fields (#149286)

For mutable and const fields, we have two bits in InlineDescriptor,
which both get inherited down the hierarchy. When a field is both const
and mutable, we CAN read from it if it is a mutable-in-const field, but
we _can't_ read from it if it is a const-in-mutable field. We need
another bit to distinguish the two cases.

1 files changed, 48 insertions, 8 deletions

diff --git a/clang/test/AST/ByteCode/mutable.cpp b/clang/test/AST/ByteCode/mutable.cpp
index aebbea9..35c5a03 100644
--- a/clang/test/AST/ByteCode/mutable.cpp
+++ b/clang/test/AST/ByteCode/mutable.cpp
@@ -1,11 +1,7 @@
-// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -std=c++11 -verify=expected,expected11,both,both11 %s
-// RUN: %clang_cc1 -fexperimental-new-constant-interpreter -std=c++14 -verify=expected,expected14,both %s
-// RUN: %clang_cc1 -std=c++11 -verify=ref,ref11,both,both11 %s
-// RUN: %clang_cc1 -std=c++14 -verify=ref,ref14,both %s
-
-
-
-
+// RUN: %clang_cc1 -std=c++11 -verify=expected,expected11,both,both11 %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -std=c++14 -verify=expected,expected14,both        %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -std=c++11 -verify=ref,ref11,both,both11           %s
+// RUN: %clang_cc1 -std=c++14 -verify=ref,ref14,both                  %s
 
 namespace Simple {
   struct S {
@@ -26,3 +22,47 @@ namespace Simple {
   static_assert(s2.a2 == 12, ""); // both11-error {{not an integral constant expression}} \
                                   // both11-note {{initializer of 's2' is not a constant expression}}
 }
+#if __cplusplus >= 201402L
+namespace ConstInMutable {
+  class B {
+    public:
+
+    const int f;
+    constexpr B() : f(12) {}
+  };
+  class A {
+    public:
+    mutable B b;
+    constexpr A() = default;
+  };
+  constexpr int constInMutable() {
+    A a;
+
+    int *m = (int*)&a.b.f;
+    *m = 12; // both-note {{modification of object of const-qualified type 'const int' is not allowed in a constant expression}}
+    return 1;
+  }
+  static_assert(constInMutable() == 1, ""); // both-error {{not an integral constant expression}} \
+                                            // both-note {{in call to}}
+}
+
+namespace MutableInConst {
+  class C {
+  public:
+    mutable int c;
+    constexpr C() : c(50) {}
+  };
+  class D {
+  public:
+    C c;
+    constexpr D() {}
+  };
+  constexpr int mutableInConst() {
+    const D d{};
+    int *m = (int*)&d.c.c;
+    *m = 12;
+    return 1;
+  }
+  static_assert(mutableInConst() == 1, "");
+}
+#endif