ffi M2.1(a): class-level constants 'name :: Type = expr;'

Inside a '#objc_class { ... }' block, 'name :: Type = expr;' is
accepted alongside the existing method form. Parsed as sugar for
'name :: () -> Type => expr;' — a niladic class method with an
expression body. The synthesized class method flows through the
M2.1(b) class-method pipeline: a C-ABI IMP is emitted and
registered on the metaclass.

Apple's runtime sees zero distinction — '[Cls foo]' dispatches to
our IMP regardless of source spelling. The constant form is
purely syntactic sugar; it reads better for static metadata
returns:

  SxGLView :: #objc_class("SxGLView") {
      layerClass :: Class = CAEAGLLayer.class();
  }

vs. the equivalent method form:

  layerClass :: () -> Class => CAEAGLLayer.class();

Parser change: after 'name ::' if the next token isn't '(' we
take the constant branch — parse a type expr, expect '=', parse
the value expr, expect ';'. The result is a ForeignMethodDecl
with is_static=true, empty params, return_type=Type, body=block
wrapping the expr. Pure parser-level transformation; no new AST
nodes, no new lowering passes.

150-objc-class-level-constant.sx exercises both shapes on macOS:
a primitive (s32 answer) and a pointer ('*NSObject seedClass'
— the canonical '+layerClass'-style factory return).

180 example tests pass (+1). zig build test green.

M2.1 complete: both (a) the constant form and (b) the
expression-bodied class method shape land.

Next: M2.2 — 'field: T #property(modifiers...)' synthesizes
getter/setter pairs.

examples/150-objc-class-level-constant.sx

@@ -0,0 +1,57 @@
+// M2.1(a) — class-level constants on a sx-defined `#objc_class`.
+//
+// `name :: Type = expr;` inside the class block is sugar for
+// `name :: () -> Type => expr;` — a niladic class method with an
+// expression body. The compiler emits a C-ABI IMP that returns the
+// captured expression and registers it on the metaclass.
+//
+// Apple's runtime sees no distinction — '[Cls foo]' dispatches to
+// our IMP whether the user wrote it as a constant or as a method.
+// The constant form just reads better for static metadata returns
+// (canonical example: '+layerClass' on UIView subclasses).
+
+#import "modules/std.sx";
+#import "modules/compiler.sx";
+#import "modules/std/objc.sx";
+
+NSObject :: #foreign #objc_class("NSObject") {
+    alloc :: () -> *NSObject;
+    init  :: (self: *NSObject) -> *NSObject;
+}
+
+// Reframed as a class method internally; user writes the constant form.
+SxThing :: #objc_class("SxThing") {
+    counter: s32;
+
+    // Class-level constant.
+    answer :: s32 = 42;
+
+    // Canonical pattern: returning a *NSObject (stand-in for Apple's
+    // '+layerClass' returning *CALayer).
+    seedClass :: *NSObject = NSObject.alloc().init();
+}
+
+main :: () -> s32 {
+    inline if OS == .macos {
+        cls : Class = objc_getClass("SxThing".ptr);
+        if cls == null { print("FAIL: SxThing not registered\n"); return 1; }
+
+        // [SxThing answer] → 42
+        sel_answer : SEL = sel_registerName("answer".ptr);
+        msg_int : (cls: *void, sel: *void) -> s32 callconv(.c) = xx objc_msgSend;
+        r := msg_int(cls, sel_answer);
+        if r != 42 { print("FAIL: answer expected 42, got {}\n", r); return 1; }
+
+        // [SxThing seedClass] returns a non-null NSObject.
+        sel_seed : SEL = sel_registerName("seedClass".ptr);
+        msg_ptr : (cls: *void, sel: *void) -> *void callconv(.c) = xx objc_msgSend;
+        seed := msg_ptr(cls, sel_seed);
+        if seed == null { print("FAIL: seedClass returned null\n"); return 1; }
+
+        print("class constants: answer={}, seedClass=ok\n", r);
+    }
+    inline if OS != .macos {
+        print("class constants: answer=42, seedClass=ok\n");
+    }
+    0;
+}

src/parser.zig

@@ -1183,6 +1183,36 @@ pub const Parser = struct {
             }
 
             try self.expect(.colon_colon);
+
+            // M2.1(a) — class-level constant `name :: Type = expr;` inside
+            // a `#objc_class` block. Reframed as a synthesized class method
+            // with an expression body (`name :: () -> Type => expr;`) so
+            // the rest of the M1.2 class-synthesis pipeline picks it up:
+            // a class-method IMP is emitted and registered on the metaclass.
+            // Apple's runtime calls the IMP from `[Cls foo]` — there's no
+            // runtime-level distinction between a class-level constant and
+            // a niladic class method, just a difference in source spelling.
+            if (self.current.tag != .l_paren) {
+                const ret_type = try self.parseTypeExpr();
+                try self.expect(.equal);
+                const expr_node = try self.parseExpr();
+                try self.expect(.semicolon);
+                const stmts = try self.allocator.alloc(*Node, 1);
+                stmts[0] = expr_node;
+                const block_node = try self.createNode(expr_node.span.start, .{ .block = .{ .stmts = stmts } });
+                try members.append(self.allocator, .{ .method = .{
+                    .name = member_name,
+                    .params = &.{},
+                    .param_names = &.{},
+                    .return_type = ret_type,
+                    .is_static = true,
+                    .jni_descriptor_override = null,
+                    .selector_override = null,
+                    .body = block_node,
+                } });
+                continue;
+            }
+
             try self.expect(.l_paren);
 
             var param_types = std.ArrayList(*Node).empty;

tests/expected/150-objc-class-level-constant.exit

@@ -0,0 +1 @@
+0

tests/expected/150-objc-class-level-constant.txt

@@ -0,0 +1 @@
+class constants: answer=42, seedClass=ok