From 83b244475a9a0af788715f76926a744e3d1b8e08 Mon Sep 17 00:00:00 2001
From: Joseph Ferano <joseph@ferano.io>
Date: Fri, 25 Sep 2026 10:30:52 +0700
Subject: [PATCH] A refusal that suggests a fix suggests one that compiles, for
 vec-new, map-new and a near miss that is a value

---
 TODO.org          |  8 ++++++++
 lib/check.ml      | 34 ++++++++++++++++++++++++++++++----
 test/test_flan.ml | 22 ++++++++++++++++++++++
 3 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/TODO.org b/TODO.org
index c94d08a4..2c65948b 100644
--- a/TODO.org
+++ b/TODO.org
@@ -1034,6 +1034,14 @@ should not pay for identity and metadata. Not implemented.
 function nosuch" twice at the same place and counts 2 errors — once from the
 abstract pass and once from the instantiation.
 
+** DONE Two refusals suggested something that does not compile
+CLOSED: [2026-09-25]
+=vec-new= and =map-new= with no type no longer say "or give the binding a type";
+they name the type arguments alone, and =(the T expr)= joins them when it lands.
+An unknown call whose near miss is a value — =(context-allocator)= against
+=context/allocator=, or a global — says the name is a value written without
+parentheses, and names no call at all when the call had arguments.
+
 * Backends
 
 ** DONE The x86 backend tracks LLVM at -O0
diff --git a/lib/check.ml b/lib/check.ml
index 40a65e3c..34c05c4d 100644
--- a/lib/check.ml
+++ b/lib/check.ml
@@ -6751,7 +6751,7 @@ and vec_new_elem ctx ~want loc args =
      | _ ->
        fail loc
          "nothing here says what (vec-new) is a Vec of — write the element \
-          type, as (vec-new i32), or give the binding a type")
+          type, as (vec-new i32)")
 
 (* A type written as an argument to vec-new or map-new, read back out of the
    expression Parse made of it. Only the shapes that cannot be a value there:
@@ -6817,18 +6817,18 @@ and map_new_types ctx ~want loc args =
   | a :: _ when type_of_expr a <> None ->
     fail loc
       "(map-new) names a key and no value — write both, as (map-new string \
-       i32), or give the binding a type"
+       i32)"
   | { Ast.e = Ast.Var k; _ } :: rest when is_type k && rest = [] ->
     fail loc
       "(map-new %s) names a key and no value — write both, as (map-new %s \
-       i32), or give the binding a type" k k
+       i32)" k k
   | _ ->
     (match want with
      | Some (Types.Map (k, v)) -> k, v, args
      | _ ->
        fail loc
          "nothing here says what (map-new) maps — write the key and value \
-          types, as (map-new string i32), or give the binding a type")
+          types, as (map-new string i32)")
 
 (* The element type, or the reason this is not a Vec. *)
 and vec_elem loc what (t : Types.t) =
@@ -9219,7 +9219,33 @@ and ordinary_call ctx ~want loc name args =
           | Some _ as m -> m
           | None -> if capitalised then near_miss ctx.env name else None
         in
+        (* A near miss that names a value rather than a function is still the
+           near miss, but [(m)] would be refused in its turn, so the sentence
+           says how that name is written instead. *)
+        let callable m =
+          let fn_ty = function
+            | Types.Fn _ | Types.CFn _ | Types.Dyn -> true
+            | _ -> false
+          in
+          match lookup ctx m with
+          | Some b -> fn_ty b.bty
+          | None ->
+            match Hashtbl.find_opt ctx.env.globals m with
+            | Some (ty, _) -> fn_ty ty
+            | None ->
+              not (List.mem m [ "true"; "false"; "nil"; "None";
+                                "context/allocator"; "context/temp" ])
+        in
         match guess with
+        | Some m when not (callable m) ->
+          if args = [] then
+            Loc.failk "check/unknown-function" loc
+              "unknown function %s — did you mean %s? It is a value and not a \
+               function, so it is written without parentheses" name m
+          else
+            Loc.failk "check/unknown-function" loc
+              "unknown function %s. The nearest name, %s, is a value and not a \
+               function" name m
         | Some m ->
           Loc.failk "check/unknown-function" loc
             "unknown function %s — did you mean %s?" name m
diff --git a/test/test_flan.ml b/test/test_flan.ml
index 758848c1..b24cb9f6 100644
--- a/test/test_flan.ml
+++ b/test/test_flan.ml
@@ -6375,6 +6375,28 @@ let () =
     "(defmacro idm [x] x) \
      (defn f [] u64 (idm 18446744073709551615))";
 
+  (* ── Suggestions that compile ─────────────────────────────────── *)
+  (* A let binding has no type slot, so the refusal names only the spelling
+     that works. *)
+  rejects_check "vec-new with no element type names only the type argument"
+    "(defn f [] i32 (let [v (vec-new)] 0))"
+    ~needle:"as (vec-new i32)";
+  (match checked "(defn f [] i32 (let [m (map-new)] 0))" with
+   | _ -> check "map-new with no types is refused" false
+   | exception Loc.Error d ->
+     check "map-new's refusal does not suggest a binding type"
+       (not (contains d.Loc.dmsg "binding")));
+  (* The near miss is a value, and is suggested without the parentheses that
+     would make it a refused call. *)
+  rejects_check "a near miss that is a value says it is written bare"
+    "(defn f [] i32 (let [a (context-allocator)] 0))"
+    ~needle:"did you mean context/allocator? It is a value and not a function";
+  accepts "the bare spelling that refusal names compiles"
+    "(defn f [] i32 (let [a context/allocator] 0))";
+  rejects_check "a near miss that is a function keeps the plain suggestion"
+    "(defn foo [] i32 1) (defn f [] i32 (fooo))"
+    ~needle:"did you mean foo?";
+
   (* ── The acceptance program checks end to end ──────────────────── *)
   accepts "calc-me.flan type checks"
     (In_channel.with_open_bin "../calc-me.flan" In_channel.input_all);