From 16640ddde1fd55b821e0473996457d2b05514763 Mon Sep 17 00:00:00 2001
From: Jan Klaas Kollhof <jan@kollhof.net>
Date: Sun, 14 Jun 2026 19:35:17 +0100
Subject: [PATCH] fix(scopes): enum member names are not lexical bindings

Enum members (Some/None) do not leak into the lexical scope -- they are
reached via Enum.Some / destructure, a type-system concern. The
lexical-scopes pass now treats a constructor name like a record field
name: neither bound nor resolved; only the payload types resolve. Fixes
the earlier walk_type_member registering Some/None as binds.
---
 src/passes/scopes/mod.rs               | 30 +++++++++++++-------------
 src/passes/scopes/test_scope_types.fnk | 10 ++++-----
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/src/passes/scopes/mod.rs b/src/passes/scopes/mod.rs
index b8ab3c3..e27fac6 100644
--- a/src/passes/scopes/mod.rs
+++ b/src/passes/scopes/mod.rs
@@ -618,10 +618,12 @@ fn walk_stmts<'src>(ast: &Ast<'src>, stmts: &[AstId], scope: ScopeId, ctx: &mut
 /// Walk one member/field line of a `type` / `enum` / `union` body.
 ///
 /// `is_enum` selects the constructor-minting semantics: in an `enum`, the
-/// leading name of a member is a *binding* (a minted constructor), and only
-/// the payload is resolved as type references. In `type`/`union`, names that
-/// are field labels are declarations (not resolved); everything else is a
-/// type reference.
+/// leading name of a member is a *declaration* (a minted constructor) that does
+/// NOT leak as a lexical binding -- it is reached via `Enum.Some` / destructure
+/// (a type-system concern), so the lexical-scopes pass treats it like a record
+/// field name: not bound, not resolved. Only the payload is resolved as type
+/// references. In `type`/`union`, field-label names are likewise declarations
+/// (not resolved); everything else is a type reference.
 fn walk_type_member<'src>(ast: &Ast<'src>, id: AstId, scope: ScopeId, ctx: &mut Ctx<'src>, is_enum: bool) {
   let kind = ast.nodes.get(id).kind.clone();
   match kind {
@@ -642,23 +644,21 @@ fn walk_type_member<'src>(ast: &Ast<'src>, id: AstId, scope: ScopeId, ctx: &mut
       }
     }
 
-    // Enum constructor with a payload: `Some T`. The constructor name (func)
-    // is minted (a binding); the payload args are type references.
-    NodeKind::Apply { func, args } if is_enum => {
-      register_pattern_binds(ast, func, scope, ctx);
+    // Enum constructor with a payload: `Some T`. The constructor name (func) is
+    // a declaration that does not leak lexically -- skip it; resolve only the
+    // payload args as type references.
+    NodeKind::Apply { args, .. } if is_enum => {
       for &arg_id in args.items.iter() {
         walk_node(ast, arg_id, scope, ctx);
       }
     }
 
-    // A bare name member.
-    NodeKind::Ident(_) | NodeKind::SynthIdent(_) if is_enum => {
-      // Nullary enum constructor `None` -- mint it.
-      register_pattern_binds(ast, id, scope, ctx);
-    }
+    // Nullary enum constructor `None`: a declaration, neither bound nor
+    // resolved at the lexical-scopes level.
+    NodeKind::Ident(_) | NodeKind::SynthIdent(_) if is_enum => {}
 
-    // type tuple positional / union member / enum payload-less non-ident:
-    // a type reference (or sub-expression to resolve).
+    // type tuple positional / union member: a type reference (or
+    // sub-expression to resolve).
     _ => walk_node(ast, id, scope, ctx),
   }
 }
diff --git a/src/passes/scopes/test_scope_types.fnk b/src/passes/scopes/test_scope_types.fnk
index 6c47f83..878dd18 100644
--- a/src/passes/scopes/test_scope_types.fnk
+++ b/src/passes/scopes/test_scope_types.fnk
@@ -31,9 +31,11 @@ test 'record field names are not references', fn:
       bind 0, 'Foo'
 
 
-# enum members MINT constructors: the constructor name binds, the payload type
-# resolves against the generic param.
-test 'enum members mint constructors', fn:
+# enum member names do NOT leak as lexical bindings (reached via Enum.Some /
+# destructure, a type-system concern). The lexical-scopes pass treats the
+# constructor name like a record field name: not bound, not resolved. Only the
+# generic param binds and the payload type resolves against it.
+test 'enum member names are not lexical binds', fn:
   expect scope ƒink:
     Option = enum T:
       Some T
@@ -43,7 +45,5 @@ test 'enum members mint constructors', fn:
 
       scope 7, 'enum',
         bind 1, 'T'
-        bind 3, 'Some'
         ref 'T', 1
-        bind 6, 'None'
       bind 0, 'Option'