From 6e977342111c9b0359c7952dbd5bed944ca85739 Mon Sep 17 00:00:00 2001
From: Folkert <folkert@folkertdev.nl>
Date: Sun, 15 Mar 2020 14:41:51 +0100
Subject: [PATCH] ensure Bit/Enum patterns are considered exhaustive

---
 compiler/mono/src/pattern.rs | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/compiler/mono/src/pattern.rs b/compiler/mono/src/pattern.rs
index 638587a044..f8f4183fa2 100644
--- a/compiler/mono/src/pattern.rs
+++ b/compiler/mono/src/pattern.rs
@@ -39,9 +39,35 @@ fn simplify<'a>(pattern: &crate::expr::Pattern<'a>) -> Pattern {
         FloatLiteral(v) => Literal(Literal::Float(*v)),
         StrLiteral(v) => Literal(Literal::Str(v.clone())),
 
-        // TODO make sure these are exhaustive
-        BitLiteral(b) => Literal(Literal::Bit(*b)),
-        EnumLiteral { tag_id, .. } => Literal(Literal::Byte(*tag_id)),
+        // To make sure these are exhaustive, we have to "fake" a union here
+        // TODO: use the hash or some other integer to discriminate between constructors
+        BitLiteral(b) => {
+            let union = Union {
+                alternatives: vec![
+                    Ctor {
+                        name: TagName::Global("False".into()),
+                        arity: 0,
+                    },
+                    Ctor {
+                        name: TagName::Global("True".into()),
+                        arity: 0,
+                    },
+                ],
+            };
+
+            Ctor(union, TagName::Global(format!("{}", b).into()), vec![])
+        }
+        EnumLiteral { tag_id, enum_size } => {
+            let alternatives = (0..*enum_size)
+                .map(|id| Ctor {
+                    name: TagName::Global(format!("{}", id).into()),
+                    arity: 0,
+                })
+                .collect();
+
+            let union = Union { alternatives };
+            Ctor(union, TagName::Global(format!("{}", tag_id).into()), vec![])
+        }
 
         Underscore => Anything,
         Identifier(_) => Anything,