comptime VM: Phase 3 — find_type + type_field_count reflection readers

First read-only compiler-API reflection readers, bound the same way as the
intern/text_of seed (compiler_lib.bound_fns + Vm.callCompilerFn, native on flat
memory, no marshaling). A type handle is a plain u32 TypeId (like StringId), so
both stay clean scalar host-calls:

  find_type(name: StringId) -> TypeId          (TypeTable.findByName; unresolved/0 if absent)
  type_field_count(t: TypeId) -> i64           (new TypeTable.memberCount; loud-bail, no silent 0)

memberCount is the single source both the legacy handler and the VM read, so the
two paths can't drift. find_type returns a non-optional TypeId using the
unresolved(0) sentinel for not-found rather than ?Type — a Type value is
.any-typed (which the flat-memory VM does not represent) and an optional can't
cross the legacy<->VM eval boundary; unresolved is the project-blessed "no type"
marker.

Example 0628 chains intern -> find_type -> type_field_count (+ a not-found
lookup), folded at #run, VM-HANDLED natively. VM unit test added.

Parity 689/689 (gate OFF and -Dcomptime-flat).

src/ir/compiler_lib.zig

@@ -47,6 +47,8 @@ pub const BoundFn = struct {
 pub const bound_fns = [_]BoundFn{
     .{ .sx_name = "intern", .handler = handleIntern },
     .{ .sx_name = "text_of", .handler = handleTextOf },
+    .{ .sx_name = "find_type", .handler = handleFindType },
+    .{ .sx_name = "type_field_count", .handler = handleTypeFieldCount },
 };
 
 /// Look up a compiler function by its sx name. Returns null when the name is not
@@ -82,3 +84,30 @@ fn handleTextOf(interp: *Interpreter, args: []const Value) InterpError!Value {
     const id: StringId = @enumFromInt(@as(u32, @intCast(args[0].int)));
     return Value{ .string = interp.module.types.getString(id) };
 }
+
+/// `find_type(name: StringId) -> TypeId` — look up a named type (struct / enum /
+/// union / tagged-union / error-set) by its interned name and return its handle.
+/// A name with no matching type yields the dedicated `unresolved` sentinel (a
+/// `TypeId` of 0), the codebase-blessed "no type" marker — NOT an `?Type` (a
+/// `Type` value is `.any`-typed, which the flat-memory VM does not represent, and
+/// an optional can't cross the legacy↔VM eval boundary). The caller checks the
+/// handle against 0 / `unresolved`. The VM mirrors this in `comptime_vm.callCompilerFn`.
+fn handleFindType(interp: *Interpreter, args: []const Value) InterpError!Value {
+    if (args.len != 1 or args[0] != .int) return error.TypeError;
+    if (args[0].int < 0 or args[0].int > std.math.maxInt(u32)) return error.TypeError;
+    const name: StringId = @enumFromInt(@as(u32, @intCast(args[0].int)));
+    const tid = interp.module.types.findByName(name) orelse types.TypeId.unresolved;
+    return Value{ .int = tid.index() };
+}
+
+/// `type_field_count(t: TypeId) -> i64` — the member count of an aggregate type
+/// (struct/union/tagged-union fields, enum variants, array/vector length), read
+/// through `TypeTable.memberCount`. A type with no member count (scalar, pointer,
+/// the `unresolved` sentinel, …) is a loud error — never a silent 0.
+fn handleTypeFieldCount(interp: *Interpreter, args: []const Value) InterpError!Value {
+    if (args.len != 1 or args[0] != .int) return error.TypeError;
+    if (args[0].int < 0 or args[0].int > std.math.maxInt(u32)) return error.TypeError;
+    const tid: types.TypeId = @enumFromInt(@as(u32, @intCast(args[0].int)));
+    const count = interp.module.types.memberCount(tid) orelse return error.TypeError;
+    return Value{ .int = count };
+}

src/ir/comptime_vm.test.zig

@@ -769,6 +769,70 @@ test "comptime_vm exec: compiler-fn intern/text_of round-trip (native, no legacy
     try std.testing.expectEqual(@as(i64, 5), toI64(try v.run(module.getFunction(main_id), &.{})));
 }
 
+test "comptime_vm exec: compiler-fn find_type + type_field_count (native reflection)" {
+    const alloc = std.testing.allocator;
+    var module = Module.init(alloc);
+    defer module.deinit();
+
+    // A struct `Point { x, y, z }` registered in the type table (the thing the
+    // reflection readers look up by name and count the fields of).
+    const point_name = module.types.internString("Point");
+    const pfields = [_]types.TypeInfo.StructInfo.Field{
+        .{ .name = module.types.internString("x"), .ty = .i64 },
+        .{ .name = module.types.internString("y"), .ty = .i64 },
+        .{ .name = module.types.internString("z"), .ty = .i64 },
+    };
+    _ = module.types.intern(.{ .@"struct" = .{ .name = point_name, .fields = &pfields } });
+
+    // extern find_type(name: u32) -> u32 [compiler]   (FuncId 0, no body)
+    const fp = [_]Function.Param{.{ .name = module.types.internString("name"), .ty = .u32 }};
+    var ffb = Fb.init(alloc, &fp, .u32);
+    ffb.func.is_extern = true;
+    ffb.func.compiler_welded = true;
+    ffb.func.name = module.types.internString("find_type");
+    const find_id = module.addFunction(ffb.func);
+
+    // extern type_field_count(t: u32) -> i64 [compiler]   (FuncId 1, no body)
+    const cp = [_]Function.Param{.{ .name = module.types.internString("t"), .ty = .u32 }};
+    var cfb = Fb.init(alloc, &cp, .i64);
+    cfb.func.is_extern = true;
+    cfb.func.compiler_welded = true;
+    cfb.func.name = module.types.internString("type_field_count");
+    const count_id = module.addFunction(cfb.func);
+
+    // main(): return type_field_count(find_type(intern_id_of("Point")))   → 3
+    // ("Point" is already interned above; pass its StringId directly.)
+    var fb = Fb.init(alloc, &.{}, .i64);
+    const b0 = fb.block(&.{});
+    const nm = fb.add(b0, inst(.{ .const_int = @intFromEnum(point_name) }, .u32));
+    const nargs = [_]Ref{ref(nm)};
+    const tid = fb.add(b0, inst(.{ .call = .{ .callee = find_id, .args = &nargs } }, .u32));
+    const targs = [_]Ref{ref(tid)};
+    const cnt = fb.add(b0, inst(.{ .call = .{ .callee = count_id, .args = &targs } }, .i64));
+    _ = fb.add(b0, inst(.{ .ret = .{ .operand = ref(cnt) } }, .void));
+    const main_id = module.addFunction(fb.func);
+
+    var v = vm.Vm.init(alloc);
+    v.table = &module.types;
+    v.module = &module;
+    defer v.deinit();
+    try std.testing.expectEqual(@as(i64, 3), toI64(try v.run(module.getFunction(main_id), &.{})));
+
+    // A name with no matching type → the `unresolved` (0) sentinel.
+    const missing = module.types.internString("Nope");
+    var mfb = Fb.init(alloc, &.{}, .u32);
+    const mb = mfb.block(&.{});
+    const mnm = mfb.add(mb, inst(.{ .const_int = @intFromEnum(missing) }, .u32));
+    const margs = [_]Ref{ref(mnm)};
+    const mres = mfb.add(mb, inst(.{ .call = .{ .callee = find_id, .args = &margs } }, .u32));
+    _ = mfb.add(mb, inst(.{ .ret = .{ .operand = ref(mres) } }, .void));
+    const missing_main = module.addFunction(mfb.func);
+    try std.testing.expectEqual(
+        @as(i64, @intFromEnum(TypeId.unresolved)),
+        toI64(try v.run(module.getFunction(missing_main), &.{})),
+    );
+}
+
 test "comptime_vm exec: func_ref + call_indirect dispatch" {
     const alloc = std.testing.allocator;
     var module = Module.init(alloc);

src/ir/comptime_vm.zig

@@ -1011,6 +1011,30 @@ pub const Vm = struct {
             if (text.len > 0) @memcpy(try self.machine.bytes(data, text.len), text);
             return try self.makeSlice(table, data, text.len);
         }
+        // ── read-only reflection readers (Phase 3) ──────────────────────────
+        // Type handle = a u32 `TypeId` (a word), exactly like `StringId` — so
+        // these mirror intern/text_of's shape: word in, word out, no marshaling.
+        if (std.mem.eql(u8, name, "find_type")) {
+            if (args.len != 1) return self.failMsg("comptime find_type: expected one StringId arg");
+            const raw = frame.get(args[0].index());
+            if (raw > std.math.maxInt(u32)) return self.failMsg("comptime find_type: StringId out of range");
+            const sid: types.StringId = @enumFromInt(@as(u32, @intCast(raw)));
+            // Not found → the dedicated `unresolved` (0) sentinel, never a real
+            // type id (mirrors `compiler_lib.handleFindType`).
+            const tid = table.findByName(sid) orelse TypeId.unresolved;
+            return @as(Reg, tid.index());
+        }
+        if (std.mem.eql(u8, name, "type_field_count")) {
+            if (args.len != 1) return self.failMsg("comptime type_field_count: expected one TypeId arg");
+            const raw = frame.get(args[0].index());
+            if (raw > std.math.maxInt(u32)) return self.failMsg("comptime type_field_count: TypeId out of range");
+            const tid: TypeId = @enumFromInt(@as(u32, @intCast(raw)));
+            // Same `TypeTable.memberCount` the legacy handler reads → no drift; a
+            // type with no member count bails loudly (no silent 0).
+            const count = table.memberCount(tid) orelse
+                return self.failMsg("comptime type_field_count: type has no field/variant count");
+            return @as(Reg, @bitCast(count));
+        }
         return null; // not a known compiler function → caller bails to legacy
     }
 

src/ir/types.zig

@@ -480,6 +480,26 @@ pub const TypeTable = struct {
         return null;
     }
 
+    /// Member count of an aggregate type: struct/union/tagged-union fields, enum
+    /// variants, or array/vector length. Returns null for a type that has no
+    /// member count (a scalar, pointer, the `unresolved` sentinel, …) — so a
+    /// caller bails loudly rather than reading a silent 0. The comptime
+    /// compiler-API reflection reader `type_field_count` rides on this (both the
+    /// legacy `compiler_lib` handler and the flat-memory VM call it, so the two
+    /// paths can never drift). Out-of-range ids return null, not a panic.
+    pub fn memberCount(self: *const TypeTable, id: TypeId) ?i64 {
+        if (id.index() >= self.infos.items.len) return null;
+        return switch (self.get(id)) {
+            .@"struct" => |s| @intCast(s.fields.len),
+            .@"union" => |u| @intCast(u.fields.len),
+            .tagged_union => |u| @intCast(u.fields.len),
+            .@"enum" => |e| @intCast(e.variants.len),
+            .array => |a| @intCast(a.length),
+            .vector => |v| @intCast(v.length),
+            else => null,
+        };
+    }
+
     /// Source-sensitive variant of `findByName`: asserts at most one named type
     /// matches, then returns it (or null). Quarantines the global first-match
     /// scan — new resolver code that must not silently pick a first-of-many