From 24af13e7e07005c69088934e4307f72d633b6bbe Mon Sep 17 00:00:00 2001
From: Brummel <mould@mycelium.de>
Date: Sun, 10 May 2026 21:25:26 +0200
Subject: [PATCH] iter 23.1.3 fixup: cover AmbiguousType branch with
 cross-module test

---
 crates/ailang-check/src/lib.rs | 82 ++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/crates/ailang-check/src/lib.rs b/crates/ailang-check/src/lib.rs
index 5990123..2757758 100644
--- a/crates/ailang-check/src/lib.rs
+++ b/crates/ailang-check/src/lib.rs
@@ -3793,6 +3793,88 @@ mod tests {
         assert!(diags.is_empty(), "expected green; got {diags:?}");
     }
 
+    /// Iter 23.1: the new bare-type-name imports-fallback in
+    /// `Term::Ctor` synth (symmetric to `Pattern::Ctor`'s Iter-15a
+    /// fallback) must report `ambiguous-type` when two imported
+    /// modules each declare a type with the same bare name, so that
+    /// a future fixture importing two prelude-shaped modules cannot
+    /// silently resolve to one of them.
+    #[test]
+    fn cross_module_term_ctor_ambiguous_type_errors() {
+        // Two different libs, each declaring a type `T` (intentional clash)
+        // with a single ctor each.
+        let lib_a = Module {
+            schema: SCHEMA.into(),
+            name: "lib_a".into(),
+            imports: vec![],
+            defs: vec![Def::Type(TypeDef {
+                name: "T".into(),
+                vars: vec![],
+                ctors: vec![Ctor { name: "MkA".into(), fields: vec![] }],
+                doc: None,
+                drop_iterative: false,
+            })],
+        };
+        let lib_b = Module {
+            schema: SCHEMA.into(),
+            name: "lib_b".into(),
+            imports: vec![],
+            defs: vec![Def::Type(TypeDef {
+                name: "T".into(),
+                vars: vec![],
+                ctors: vec![Ctor { name: "MkB".into(), fields: vec![] }],
+                doc: None,
+                drop_iterative: false,
+            })],
+        };
+        let consumer = Module {
+            schema: SCHEMA.into(),
+            name: "use_both".into(),
+            imports: vec![
+                Import { module: "lib_a".into(), alias: None },
+                Import { module: "lib_b".into(), alias: None },
+            ],
+            defs: vec![fn_def(
+                "f",
+                Type::Fn {
+                    params: vec![],
+                    ret: Box::new(Type::int()),
+                    effects: vec![],
+                    param_modes: vec![],
+                    ret_mode: ParamMode::Implicit,
+                },
+                vec![],
+                // Bare type_name `T` — both lib_a and lib_b match.
+                Term::Match {
+                    scrutinee: Box::new(Term::Ctor {
+                        type_name: "T".into(),
+                        ctor: "MkA".into(),
+                        args: vec![],
+                    }),
+                    arms: vec![Arm {
+                        pat: Pattern::Wild,
+                        body: Term::Lit { lit: Literal::Int { value: 0 } },
+                    }],
+                },
+            )],
+        };
+        let mut modules = BTreeMap::new();
+        modules.insert("lib_a".into(), lib_a);
+        modules.insert("lib_b".into(), lib_b);
+        modules.insert("use_both".into(), consumer);
+        let ws = Workspace {
+            entry: "use_both".into(),
+            modules,
+            root_dir: std::path::PathBuf::from("."),
+            registry: ailang_core::workspace::Registry::default(),
+        };
+        let diags = check_workspace(&ws);
+        assert!(
+            diags.iter().any(|d| d.code == "ambiguous-type"),
+            "expected ambiguous-type diagnostic; got {diags:?}"
+        );
+    }
+
     /// Iter 23.1: the prelude module is implicitly imported into
     /// every user module. A user module that pattern-matches on
     /// `LT` / `EQ` / `GT` without an explicit