Extract can/ into its own crate, plus its deps

compiler/can/src/expected.rs

@@ -0,0 +1,66 @@
+use crate::pattern::Pattern;
+use roc_region::all::{Located, Region};
+use roc_types::types::{AnnotationSource, PReason, Reason};
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Expected<T> {
+    NoExpectation(T),
+    FromAnnotation(Located<Pattern>, usize, AnnotationSource, T),
+    ForReason(Reason, T, Region),
+}
+
+/// Like Expected, but for Patterns.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum PExpected<T> {
+    NoExpectation(T),
+    ForReason(PReason, T, Region),
+}
+
+impl<T> PExpected<T> {
+    pub fn get_type(self) -> T {
+        match self {
+            PExpected::NoExpectation(val) => val,
+            PExpected::ForReason(_, val, _) => val,
+        }
+    }
+
+    pub fn get_type_ref(&self) -> &T {
+        match self {
+            PExpected::NoExpectation(val) => val,
+            PExpected::ForReason(_, val, _) => val,
+        }
+    }
+
+    pub fn get_type_mut_ref(&mut self) -> &mut T {
+        match self {
+            PExpected::NoExpectation(val) => val,
+            PExpected::ForReason(_, val, _) => val,
+        }
+    }
+}
+
+impl<T> Expected<T> {
+    pub fn get_type(self) -> T {
+        match self {
+            Expected::NoExpectation(val) => val,
+            Expected::ForReason(_, val, _) => val,
+            Expected::FromAnnotation(_, _, _, val) => val,
+        }
+    }
+
+    pub fn get_type_ref(&self) -> &T {
+        match self {
+            Expected::NoExpectation(val) => val,
+            Expected::ForReason(_, val, _) => val,
+            Expected::FromAnnotation(_, _, _, val) => val,
+        }
+    }
+
+    pub fn get_type_mut_ref(&mut self) -> &mut T {
+        match self {
+            Expected::NoExpectation(val) => val,
+            Expected::ForReason(_, val, _) => val,
+            Expected::FromAnnotation(_, _, _, val) => val,
+        }
+    }
+}