From e476b1e0b8d2660d163360adbb0e6d21b04af95c Mon Sep 17 00:00:00 2001
From: Markus Westerlind <marwes91@gmail.com>
Date: Sat, 16 Dec 2017 00:08:12 +0100
Subject: [PATCH] fix(check): Don't panic if a type is undefined in a variant

---
 base/src/lib.rs       |  2 ++
 base/src/macros.rs    |  1 -
 base/src/resolve.rs   |  4 +--
 base/src/types/mod.rs | 74 +++++++++++++++++++++++--------------------
 check/tests/fail.rs   | 13 ++++++++
 5 files changed, 55 insertions(+), 39 deletions(-)

diff --git a/base/src/lib.rs b/base/src/lib.rs
index 2a28392a1b..9dc5645eec 100644
--- a/base/src/lib.rs
+++ b/base/src/lib.rs
@@ -5,6 +5,8 @@
 #[macro_use]
 extern crate collect_mac;
 extern crate itertools;
+#[macro_use]
+extern crate log;
 extern crate pretty;
 #[macro_use]
 extern crate quick_error;
diff --git a/base/src/macros.rs b/base/src/macros.rs
index 220ebd423a..5aee43f795 100644
--- a/base/src/macros.rs
+++ b/base/src/macros.rs
@@ -1,4 +1,3 @@
-
 #[macro_export]
 macro_rules! ice {
     () => ({
diff --git a/base/src/resolve.rs b/base/src/resolve.rs
index 59cc76a018..7bd4c30c75 100644
--- a/base/src/resolve.rs
+++ b/base/src/resolve.rs
@@ -37,9 +37,7 @@ where
         Ok(Some(alias)) if !canonical(alias) => alias
             .typ()
             .apply_args(&typ.unapplied_args())
-            .map(|typ| {
-                Cow::Owned(canonical_alias(env, &typ, canonical).into_owned())
-            })
+            .map(|typ| Cow::Owned(canonical_alias(env, &typ, canonical).into_owned()))
             .unwrap_or(Cow::Borrowed(typ)),
         _ => Cow::Borrowed(typ),
     }
diff --git a/base/src/types/mod.rs b/base/src/types/mod.rs
index e0a0aa02d1..2aba543105 100644
--- a/base/src/types/mod.rs
+++ b/base/src/types/mod.rs
@@ -411,14 +411,18 @@ where
                 Type::Ident(ref id) => {
                     // Replace `Ident` with the alias it resolves to so that a `TypeEnv` is not
                     // needed to resolve the type later on
-                    let index = self.group
-                        .iter()
-                        .position(|alias| alias.name == *id)
-                        .expect("ICE: Alias group were not able to resolve an identifier");
-                    Some(T::from(Type::Alias(AliasRef {
-                        index: index,
-                        group: self.group.clone(),
-                    })))
+                    let replacement = self.group.iter().position(|alias| alias.name == *id).map(
+                        |index| {
+                            T::from(Type::Alias(AliasRef {
+                                index: index,
+                                group: self.group.clone(),
+                            }))
+                        },
+                    );
+                    if replacement.is_none() {
+                        info!("Alias group were not able to resolve an identifier");
+                    }
+                    replacement
                 }
                 _ => None,
             }
@@ -1885,15 +1889,15 @@ where
             }
             f.walk(rest);
         }
-        Type::Hole |
-        Type::Opaque |
-        Type::Builtin(_) |
-        Type::Variable(_) |
-        Type::Generic(_) |
-        Type::Skolem(_) |
-        Type::Ident(_) |
-        Type::Alias(_) |
-        Type::EmptyRow => (),
+        Type::Hole
+        | Type::Opaque
+        | Type::Builtin(_)
+        | Type::Variable(_)
+        | Type::Generic(_)
+        | Type::Skolem(_)
+        | Type::Ident(_)
+        | Type::Alias(_)
+        | Type::EmptyRow => (),
     }
 }
 
@@ -1922,15 +1926,15 @@ where
             }
             f.walk_mut(rest);
         }
-        Type::Hole |
-        Type::Opaque |
-        Type::Builtin(_) |
-        Type::Variable(_) |
-        Type::Generic(_) |
-        Type::Skolem(_) |
-        Type::Ident(_) |
-        Type::Alias(_) |
-        Type::EmptyRow => (),
+        Type::Hole
+        | Type::Opaque
+        | Type::Builtin(_)
+        | Type::Variable(_)
+        | Type::Generic(_)
+        | Type::Skolem(_)
+        | Type::Ident(_)
+        | Type::Alias(_)
+        | Type::EmptyRow => (),
     }
 }
 
@@ -2077,15 +2081,15 @@ where
                 Type::extend_row(types.clone(), fields, rest)
             })
         }
-        Type::Hole |
-        Type::Opaque |
-        Type::Builtin(_) |
-        Type::Variable(_) |
-        Type::Skolem(_) |
-        Type::Generic(_) |
-        Type::Ident(_) |
-        Type::Alias(_) |
-        Type::EmptyRow => None,
+        Type::Hole
+        | Type::Opaque
+        | Type::Builtin(_)
+        | Type::Variable(_)
+        | Type::Skolem(_)
+        | Type::Generic(_)
+        | Type::Ident(_)
+        | Type::Alias(_)
+        | Type::EmptyRow => None,
     }
 }
 
diff --git a/check/tests/fail.rs b/check/tests/fail.rs
index bb0311c4c3..4c145913ba 100644
--- a/check/tests/fail.rs
+++ b/check/tests/fail.rs
@@ -551,3 +551,16 @@ do x = 1
 
     assert_unify_err!(result, TypeMismatch(..));
 }
+
+#[test]
+fn undefined_type_in_variant() {
+    let _ = ::env_logger::init();
+
+    let text = r#"
+type Test = | Test In
+2
+"#;
+    let result = support::typecheck(text);
+
+    assert_err!(result, UndefinedType(..));
+}