[clang] [clang][Interp] IndirectMember initializers (PR #69900)

[Aaron Ballman via cfe-commits]

Timm =?utf-8?q?Bäder?= <tbaeder at redhat.com>,
Timm =?utf-8?q?Bäder?= <tbaeder at redhat.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/69900 at github.com>


================
@@ -1133,3 +1133,75 @@ namespace AccessOnNullptr {
                                // ref-error {{not an integral constant expression}} \
                                // ref-note {{in call to 'a2()'}}
 }
+
+namespace IndirectFieldInit {
+#if __cplusplus >= 202002L
+  /// Primitive.
+  struct Nested1 {
+    struct {
+      int first;
+    };
+    int x;
+    constexpr Nested1(int x) : first(12), x() { x = 4; }
+    constexpr Nested1() : Nested1(42) {}
+  };
+  constexpr Nested1 N1{};
+  static_assert(N1.first == 12, "");
+
+  /// Composite.
+  struct Nested2 {
+    struct First { int x = 42; };
+    struct {
+      First first;
+    };
+    int x;
+    constexpr Nested2(int x) : first(12), x() { x = 4; }
+    constexpr Nested2() : Nested2(42) {}
+  };
+  constexpr Nested2 N2{};
+  static_assert(N2.first.x == 12, "");
+
+  /// Bitfield.
+  struct Nested3 {
+    struct {
+      unsigned first : 2;
+    };
+    int x;
+    constexpr Nested3(int x) : first(3), x() { x = 4; }
+    constexpr Nested3() : Nested3(42) {}
+  };
+
+  constexpr Nested3 N3{};
+  static_assert(N3.first == 3, "");
+
+  /// Test that we get the offset right if the
+  /// record has a base.
+  struct Nested4Base {
+    int a;
+    int b;
+    char c;
+  };
+  struct Nested4 : Nested4Base{
+    struct {
+      int first;
+    };
+    int x;
+    constexpr Nested4(int x) : first(123), x() { a = 1; b = 2; c = 3; x = 4; }
+    constexpr Nested4() : Nested4(42) {}
+  };
+  constexpr Nested4 N4{};
+  static_assert(N4.first == 123, "");
+
+  struct S {
+    struct {
+      int x, y;
+    };
+
+    constexpr S(int x_, int y_) : x(x_), y(y_) {}
+  };
+
+  constexpr S s(1, 2);
+  static_assert(s.x == 1 && s.y == 2);
----------------
AaronBallman wrote:

One more test just to be sure we're getting the right field in the right place:
```
 struct S {
    struct {
      struct {
        int x, y;
      };
    };

    constexpr S(int x_, int y_) : x(x_), y(y_) {}
  };

  constexpr S s(1, 2);
  static_assert(s.x == 1 && s.y == 2);
```
(basically just adds another layer of anonymous struct obfuscation)

https://github.com/llvm/llvm-project/pull/69900