feat(test): ludic test <dir>, each test block in a process of its own

A directory stands for its *_test.ludic files and the files straight
inside any tests/ under it. The runner answers --list and runs one test
by name, and ludic test runs every block in a child process, so tests
no longer share globals. A failed expect names the file it is written
in (the path the compiler was given) and its line. Reseed.

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

selfhost/backend/emit_call.ludic

@@ -23,6 +23,12 @@ function emit_expect_fail(cond1: pointer, msgsym: pointer, got: pointer, want: p
   emit(`{lok}:\n`)
 }
 
+# an assertion names the file it is written in, as the compiler was given it, and its line
+function expect_where(e: Node) -> pointer {
+  if e.file != null { return `{e.file}:{itoa(e.line)}` }
+  return `{g_src_name}:{itoa(e.line)}`
+}
+
 # lowercase an ASCII identifier (for #62 package-namespace aliasing: Foo -> foo)
 function ns_lower(s: pointer) -> pointer {
   let n = cstr_len(s)
@@ -673,7 +679,7 @@ function emit_call(e: Node) -> Val {
     g_uses_expect = true
     let a = emit_expr(e.kids[0])
     let c = emit_bind(`icmp ne i32 {a.code}, 0`)
-    let msg = emit_str_const(`{g_src_name}:{itoa(e.line)}: expect failed`)
+    let msg = emit_str_const(`{expect_where(e)}: expect failed`)
     emit_expect_fail(c, msg, "", "")
     return val("0", "void")
   }
@@ -681,7 +687,7 @@ function emit_call(e: Node) -> Val {
     g_uses_expect = true
     let a = emit_expr(e.kids[0]);  let b = emit_expr(e.kids[1])
     let c = emit_bind(`icmp eq i32 {a.code}, {b.code}`)
-    let msg = emit_str_const(`{g_src_name}:{itoa(e.line)}: expect_eq failed`)
+    let msg = emit_str_const(`{expect_where(e)}: expect_eq failed`)
     emit_expect_fail(c, msg, a.code, b.code)
     return val("0", "void")
   }
@@ -693,7 +699,7 @@ function emit_call(e: Node) -> Val {
     let isneg = emit_bind(`icmp slt i32 {d}, 0`)
     let ad = emit_bind(`select i1 {isneg}, i32 {neg}, i32 {d}`)
     let c = emit_bind(`icmp sle i32 {ad}, {tol.code}`)
-    let msg = emit_str_const(`{g_src_name}:{itoa(e.line)}: expect_near failed`)
+    let msg = emit_str_const(`{expect_where(e)}: expect_near failed`)
     emit_expect_fail(c, msg, a.code, b.code)
     return val("0", "void")
   }

selfhost/backend/emit_decl.ludic

@@ -125,6 +125,26 @@ function emit_test_runner() -> void {
   emit(`  store ptr {fval}, ptr %filter\n`)
   emit(`  br label %{lstart}\n`)
   emit(`{lstart}:\n`)
+  # `--list` names every test, one a line: `ludic test` runs each in a process of its own
+  let llist = lbl("tlist");  let lrun0 = lbl("trun0")
+  let fl0 = emit_bind("load ptr, ptr %filter")
+  let hasf0 = emit_bind(`icmp ne ptr {fl0}, null`)
+  let lcmp0 = lbl("tlcmp")
+  emit(`  br i1 {hasf0}, label %{lcmp0}, label %{lrun0}\n`)
+  emit(`{lcmp0}:\n`)
+  let listflag = emit_str_const("--list")
+  let lc = emit_bind(`call i32 @strcmp(ptr {fl0}, ptr {listflag})`)
+  let islist = emit_bind(`icmp eq i32 {lc}, 0`)
+  emit(`  br i1 {islist}, label %{llist}, label %{lrun0}\n`)
+  emit(`{llist}:\n`)
+  var li = 0
+  while li < len(g_tests) {
+    let nm = emit_str_const(g_tests[li].s)
+    emit(`  call i32 (ptr, ...) @printf(ptr @.fmt_line, ptr {nm})\n`)
+    li += 1
+  }
+  emit("  ret i32 0\n")
+  emit(`{lrun0}:\n`)
   if has_ecs() { emit("  call void @rt_init()\n") }
   emit("  call void @L_init_globals()\n")
   i = 0