From 923dd8c02fcfd5a63e85775d01821d813f9d86e0 Mon Sep 17 00:00:00 2001
From: Brummel <mould@mycelium.de>
Date: Mon, 11 May 2026 14:56:27 +0200
Subject: [PATCH] =?UTF-8?q?iter=2023.4-prep.2:=20check=20=E2=80=94=20bare-?=
 =?UTF-8?q?name=20fall-through=20to=20implicit-imported=20free=20fns?=
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---
 crates/ailang-check/src/lib.rs | 91 ++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/crates/ailang-check/src/lib.rs b/crates/ailang-check/src/lib.rs
index 2b609c7..0e5ffef 100644
--- a/crates/ailang-check/src/lib.rs
+++ b/crates/ailang-check/src/lib.rs
@@ -1806,6 +1806,34 @@ pub(crate) fn synth(
                     method: name.clone(),
                 });
                 return Ok(inst_ty);
+            } else if let Some((owner_module, raw_ty)) = env
+                .imports
+                .values()
+                .find_map(|mod_name| {
+                    env.module_globals
+                        .get(mod_name)
+                        .and_then(|mg| mg.get(name).map(|ty| (mod_name.clone(), ty.clone())))
+                })
+            {
+                // Iter 23.4-prep: bare-name fall-through to free fns of
+                // implicitly-imported modules. Today only the prelude is
+                // implicitly imported (see `build_check_env` and
+                // `check_in_workspace`'s prelude-injection at this file's
+                // ~1170 / ~1285), so the first match is unambiguous. If a
+                // second implicit import lands, the single-match-wins rule
+                // becomes a real ambiguity and this branch needs a
+                // duplicate-detection diagnostic.
+                //
+                // Qualify any bare type-cons referring to a type defined in
+                // the owning module — same treatment the dot-qualified arm
+                // below applies — so signatures cross the module boundary
+                // with fully-qualified Type::Cons.
+                let owner_types = env
+                    .module_types
+                    .get(&owner_module)
+                    .cloned()
+                    .unwrap_or_default();
+                qualify_local_types(&raw_ty, &owner_module, &owner_types)
             } else if name.matches('.').count() == 1 {
                 let (prefix, suffix) = name.split_once('.').expect("checked");
                 let target_module = match env.imports.get(prefix) {
@@ -4935,4 +4963,67 @@ mod tests {
         let diags = check_workspace(&ws);
         assert!(diags.is_empty(), "expected green; got {diags:?}");
     }
+
+    /// Iter 23.4-prep Task 2: bare-name resolution falls through to free
+    /// fns of implicitly-imported modules. The consumer calls bare `dbl`,
+    /// declared in `prelude` (the singleton implicit import today). The
+    /// pre-fix behaviour is `unbound-var` because the `Term::Var` lookup
+    /// ladder consults locals → local globals → class_methods →
+    /// dot-qualified, but never the flat free-fn tables of implicit
+    /// imports.
+    #[test]
+    fn bare_name_resolves_through_implicit_import_to_free_fn() {
+        let prelude = Module {
+            schema: SCHEMA.into(),
+            name: "prelude".into(),
+            imports: vec![],
+            defs: vec![fn_def(
+                "dbl",
+                Type::Fn {
+                    params: vec![Type::int()],
+                    ret: Box::new(Type::int()),
+                    effects: vec![],
+                    param_modes: vec![],
+                    ret_mode: ParamMode::Implicit,
+                },
+                vec!["n"],
+                Term::Var { name: "n".into() },
+            )],
+        };
+        let consumer = Module {
+            schema: SCHEMA.into(),
+            name: "m".into(),
+            imports: vec![],
+            defs: vec![fn_def(
+                "main",
+                Type::Fn {
+                    params: vec![],
+                    ret: Box::new(Type::int()),
+                    effects: vec![],
+                    param_modes: vec![],
+                    ret_mode: ParamMode::Implicit,
+                },
+                vec![],
+                Term::App {
+                    callee: Box::new(Term::Var { name: "dbl".into() }),
+                    args: vec![Term::Lit { lit: Literal::Int { value: 5 } }],
+                    tail: false,
+                },
+            )],
+        };
+        let mut modules = BTreeMap::new();
+        modules.insert("prelude".into(), prelude);
+        modules.insert("m".into(), consumer);
+        let ws = Workspace {
+            entry: "m".into(),
+            modules,
+            root_dir: std::path::PathBuf::from("."),
+            registry: ailang_core::workspace::Registry::default(),
+        };
+        let diags = check_workspace(&ws);
+        assert!(
+            diags.is_empty(),
+            "expected bare `dbl` to resolve through implicit prelude import; got {diags:?}"
+        );
+    }
 }