checker: a function named like a built-in a call always takes is refused at its declaration - function words(st, k) compiled and every call became words(n) with a pointer for n (invalid IR, far from the cause); the table is selfhost/check/check_builtins.ludic, emit_call's built-ins no find_fn guard lets a declared function take, and ludic-dev syntax --check holds it to emit_call both ways; every other built-in (buffer, floats, double, ...) yields to a declared function in the checker as it already did in codegen. string_temps' keep and cross_heap_test's keep renamed (hand, keep_cell); rejected/builtin_call_name and functions/builtin_yield with their cases (added, not run); reseeded, bootstrap-cfree fixpoint holds

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/builtin-names.md

@@ -0,0 +1,9 @@
+bump: patch
+type: fix
+**A function named like a built-in a call always takes is refused.** `function words(st, k)` compiled,
+and every call to it became the built-in `words(n)` - n zeroed ints, with a pointer for n - and LLVM
+refused the IR far from the cause. A top-level function whose name a call always takes as the
+compiler's own (`words`, `keep`, `print`, `save`, `load`, `key`, ...; the table is
+`selfhost/check/check_builtins.ludic`, held to `emit_call` by `ludic-dev syntax --check`) is now an
+error at its declaration, as `run` already was. Every other built-in (`buffer`, `floats`, `double`,
+...) yields to a function the program declares, in the checker as it already did in codegen.

examples/functions/builtin_yield.ludic

@@ -0,0 +1,11 @@
+# builtin_yield.ludic - a built-in that a declared function may take (buffer, floats, double, ...)
+# yields to it in the checker as in codegen: this `buffer` is the program's own, returning text.
+#
+# Prints:  ab 4
+program BuiltinYield {
+  function buffer(a: string, b: string) -> string { return a + b }
+  entry {
+    let s = buffer("a", "b")
+    print(`{s} {len(floats(4))}`)
+  }
+}

examples/lang/string_temps.ludic

@@ -3,7 +3,7 @@
 # has been used, and one that IS held - in a variable, handed to a function, a function's result -
 # is not. Prints 1 2 3 4 5 6 7 and `grew 0` (the heap is read on the Mac; 0 elsewhere).
 program StringTemps {
-  function keep(s: string) -> string { return s }
+  function hand(s: string) -> string { return s }
   function tag(i: int) -> string { return `t{i}` }
 
   # every shape of throwaway text, compared against itself built another way: nothing survives
@@ -29,7 +29,7 @@ program StringTemps {
     let n = string(-42)
     let t = n + "!" + n
     if n == "-42" and t == "-42!-42" { print(2) }
-    let k = keep(a + "+" + b)
+    let k = hand(a + "+" + b)
     let k2 = k + "=" + k
     if k == "dir+file" and k2 == "dir+file=dir+file" { print(3) }
     var acc = ""
@@ -37,7 +37,7 @@ program StringTemps {
     if acc == "0,1,2,3," { print(4) }
     if string(0) == "0" and string(2147483647) == "2147483647" and `{long(9000000000)}` == "9000000000" { print(5) }
     let nested = `a{`b{1 + 1}c`}d`
-    # a function's result is its caller's to keep (keep() hands back its own argument), so only
+    # a function's result is its caller's to keep (hand() hands back its own argument), so only
     # the text built round it goes
     if nested == "ab2cd" and "[" + tag(3) + "]" == "[t3]" { print(6) }
     var bad = 0

examples/rejected/builtin_call_name.ludic

@@ -0,0 +1,8 @@
+# builtin_call_name.ludic - a function named like a built-in a call always takes is refused at its
+# declaration: every call to `words` is words(n), n zeroed ints, so this helper would never run (a
+# pointer became its size). (Rejected on purpose: tools/ludic-cli/test.ludic.)
+program BuiltinCallName {
+  function words(n: int, k: string) -> string { return k }
+  function keep(s: string) -> string { return s }
+  entry { print(words(1, keep("x"))) }
+}

packages/ludic.physics/tests/cross_heap_test.ludic

@@ -44,7 +44,7 @@ program CrossHeapTest {
     cs.on[c] = false
   }
   # the ring kept round chunk (px, pz): those past it out, those in it in, and the broad phase rebuilt
-  function keep(physics_st: mut PhysicsState, cs: mut CrossState, px: int, pz: int) -> void {
+  function keep_cell(physics_st: mut PhysicsState, cs: mut CrossState, px: int, pz: int) -> void {
     for c in 0 .. N * N {
       let near = Math.abs(c % N - px) <= RING and Math.abs(c / N - pz) <= RING
       if cs.on[c] and not near { chunk_out(physics_st, cs, c) }
@@ -54,8 +54,8 @@ program CrossHeapTest {
     phys_step(physics_st)
   }
   function crossing(physics_st: mut PhysicsState, cs: mut CrossState) -> void {
-    for k in 0 .. N { keep(physics_st, cs, k, k) }
-    for k in 0 .. N { keep(physics_st, cs, N - 1 - k, N - 1 - k) }
+    for k in 0 .. N { keep_cell(physics_st, cs, k, k) }
+    for k in 0 .. N { keep_cell(physics_st, cs, N - 1 - k, N - 1 - k) }
   }
 
   test "crossing the map and back six times holds the bodies, the shapes and Jolt's bytes of the first crossing" (physics_st: mut PhysicsState, cross_st: mut CrossState) {

selfhost/check/check_builtins.ludic

@@ -0,0 +1,23 @@
+# check_builtins.ludic — the names a call always takes as the compiler's own, whatever the program
+# declares: emit_call's built-ins that no `find_fn` guard lets a declared function take. A function
+# so named is refused (ck_runtime_shadows) - a call would never reach it: a `words(st, k)` helper
+# once compiled as words(n) with a pointer for its size. Every other built-in yields to a declared
+# function, in the checker as in codegen; `ludic-dev syntax --check` holds this table to emit_call.
+function is_call_builtin(name: pointer) -> bool {
+  if (name == "apply") or (name == "assert") or (name == "bytes") or (name == "data_of") { return true }
+  if (name == "expect") or (name == "expect_eq") or (name == "expect_near") or (name == "fixed") { return true }
+  if (name == "floor") or (name == "intern") or (name == "is_owner") or (name == "is_server") { return true }
+  if (name == "keep") or (name == "key") or (name == "len") or (name == "load") { return true }
+  if (name == "local_id") or (name == "net_poll") or (name == "net_pump") or (name == "net_send") { return true }
+  if (name == "owner") or (name == "panic") or (name == "print") or (name == "push") { return true }
+  if (name == "quit") or (name == "save") or (name == "self") or (name == "serialize") { return true }
+  if (name == "set_local_id") or (name == "set_owner") or (name == "set_role") or (name == "string") { return true }
+  if (name == "sync_size") or (name == "tick_fixed") or (name == "tick_render") or (name == "view") { return true }
+  if (name == "words") or (name == "world_attach_dyn") or (name == "world_count") or (name == "world_detach_dyn") { return true }
+  if (name == "world_field_count") or (name == "world_field_id") or (name == "world_field_name") or (name == "world_field_type") { return true }
+  if (name == "world_get") or (name == "world_has") or (name == "world_kind") or (name == "world_load") { return true }
+  if (name == "world_model_id") or (name == "world_prop_count") or (name == "world_prop_id") or (name == "world_prop_name") { return true }
+  if (name == "world_query_next") or (name == "world_register_prop") or (name == "world_save") or (name == "world_set") { return true }
+  if (name == "world_size") or (name == "world_spawn") { return true }
+  return false
+}

selfhost/check/check_call.ludic

@@ -231,6 +231,15 @@ function ck_call_named(e: Node, name: pointer) -> pointer {
     return "?"
   }
   if ck_raw_builtin(name) { ck_raw(e, `{name}()`) }
+  # a built-in no call always takes (not is_call_builtin) yields to a function the program declares,
+  # as codegen's does: the checker once typed a `buffer` helper as buffer(n) while codegen called it
+  if not is_call_builtin(name) {
+    let uf = ck_fn(name)
+    if uf != null {
+      ck_vis(uf, name, e)
+      return ck_call_fn(e, name, uf)
+    }
+  }
   let bt = ck_builtin(e, name)
   if bt != null { return bt }
   let f = ck_fn(name)

selfhost/check/check_stmt.ludic

@@ -212,7 +212,7 @@ function ck_runtime_shadows() -> void {
   var u = 0
   while u < g_prog_user_end {
     let d = prog[u]
-    if d.kind == N_FN and (is_intrinsic(d.s) or is_intrinsic2(d.s)) { ck_err("shadow", d, `{d.s} is a built-in of the compiler, and a call to it would never reach this function; choose another name`) }
+    if d.kind == N_FN and (is_intrinsic(d.s) or is_intrinsic2(d.s) or is_call_builtin(d.s)) { ck_err("shadow", d, `{d.s} is a built-in of the compiler, and a call to it would never reach this function; choose another name`) }
     u += 1
   }
   var r = g_prog_user_end

tools/ludic-cli/selfhost.ludic

@@ -112,6 +112,7 @@ function selfhost_frags() -> []pointer {
   push(f, "selfhost/check/check_ops.ludic")
   push(f, "selfhost/check/check_call.ludic")
   push(f, "selfhost/check/check_stmt.ludic")
+  push(f, "selfhost/check/check_builtins.ludic")
   push(f, "selfhost/check/check_gen.ludic")
   push(f, "selfhost/check/check_gen_call.ludic")
   push(f, "selfhost/check/check_tynames.ludic")

tools/ludic-cli/syntax_gen.ludic

@@ -422,6 +422,53 @@ function sx_parser() -> int {
   return n
 }
 
+# ---- the built-ins a call always takes, held to emit_call ----
+# every `name == "x"` on one of a function's top-level `if` lines (after head, to the next function);
+# guarded skips the lines a declared function can take (`find_fn(`)
+function sx_name_tests(text: pointer, head: pointer, guarded: bool) -> []pointer {
+  let out = new []pointer
+  let n = slen(text)
+  var inside = false
+  var i = 0
+  while i < n {
+    let line = line_at(text, i)
+    i = i + slen(line) + 1
+    if s_starts(line, "function ") { inside = s_starts(line, head) }
+    else if inside and s_starts(line, "  if (") and not (guarded and s_contains(line, "find_fn(")) {
+      var at = s_index(line, "name == \"", 0)
+      while at >= 0 {
+        let a = at + 9
+        var b = a
+        while b < slen(line) and line[b] != '"' { b += 1 }
+        let w = line[a .. b]
+        if not set_has(out, w) { push(out, w) }
+        at = s_index(line, "name == \"", b)
+      }
+    }
+  }
+  return out
+}
+# selfhost/check/check_builtins.ludic's table against emit_call's unguarded built-ins, both ways
+function sx_builtins() -> int {
+  let ec = read_file("selfhost/backend/emit_call.ludic")
+  let tb = read_file("selfhost/check/check_builtins.ludic")
+  if ec == null or tb == null { push(g_sx_prob, "cannot read emit_call.ludic or check_builtins.ludic");  return 1 }
+  let want = sx_name_tests(ec, "function emit_call(", true)
+  let have = sx_name_tests(tb, "function is_call_builtin(", false)
+  var n = 0
+  var i = 0
+  while i < len(want) {
+    if not set_has(have, want[i]) { push(g_sx_prob, `emit_call always takes {want[i]}(...), and check_builtins.ludic does not refuse a function of that name - add it`);  n += 1 }
+    i += 1
+  }
+  i = 0
+  while i < len(have) {
+    if not set_has(want, have[i]) { push(g_sx_prob, `check_builtins.ludic refuses {have[i]}, which emit_call no longer always takes - drop it`);  n += 1 }
+    i += 1
+  }
+  return n
+}
+
 # ---- the command ----
 function sx_report(what: pointer) -> int {
   if len(g_sx_prob) == 0 { return 0 }
@@ -457,6 +504,7 @@ function cmd_syntax_gen() -> int {
     while i < len(ts) { sx_carries(ts[i]);  i += 1 }
     sx_docs()
     sx_parser()
+    sx_builtins()
     return sx_report("the vocabulary and what is written from it disagree")
   }
   if changed == 0 { print("  every grammar already says what ludicc --emit-syntax does") }

tools/ludic-cli/test.ludic

@@ -1375,6 +1375,8 @@ function cmd_dev_test() -> int {
   schema_case("lang/scenes", "\"scene\": \"Play\", \"layer\": \"Hud\"", "--emit-schema: code.handlers - a scene's handler, its scene and layer")
   schema_case("state/write_reach", "{\"fn\": \"log_note\", \"module\": null, \"at\": \"examples/state/write_reach.ludic:21:37\", \"slot_kind\": \"registry\", \"slot\": \"Kinds.note\", \"entry\": \"box\"}", "--emit-schema: code.fn_refs - a fn in a registry row, the field and row it fills")
   schema_case("modules/ports", "\"slot_kind\": \"port_default\", \"slot\": \"Clock.day\"", "--emit-schema: code.fn_refs - a port member's default")
+  diag_json_case("rejected/builtin_call_name", 2, "words is a built-in of the compiler, and a call to it would never reach this function; choose another name", "a function named like a built-in a call always takes (words, keep) is refused at its declaration")
+  feat_case("functions/builtin_yield", "", "ab 4", "builtin_yield.ludic (a built-in a declared function may take - buffer - yields to it in the checker as in codegen)")
   diag_json_case("rejected/i18n_keys/key_missing", 2, "the key pause.gone is not in examples/rejected/i18n_keys/lang/en.po", "a key literal en.po does not have is refused, at its line and column")
   diag_json_case("rejected/i18n_keys/key_missing", 2, "is a plural key, and examples/rejected/i18n_keys/lang/en.po:7 gives pause.resume no msgid_plural", "kn\"...\" is a plural key: en.po's entry has a msgid_plural")
   diag_json_case("rejected/i18n_keys/key_missing", 2, "trf: hud.day is given 2 value(s), and its English in examples/rejected/i18n_keys/lang/en.po has 1 hole(s)", "trf given more values than the key's English has holes: a warning")