Promote shift and subst_shift to traits

3 files changed, 42 insertions, 29 deletions

diff --git a/dhall/src/phase/mod.rs b/dhall/src/phase/mod.rs
index 97b8083..5c910bc 100644
--- a/dhall/src/phase/mod.rs
+++ b/dhall/src/phase/mod.rs
@@ -7,7 +7,7 @@ use dhall_syntax::{Const, Import, Span, SubExpr, X};
 use crate::core::context::TypecheckContext;
 use crate::core::thunk::Thunk;
 use crate::core::value::Value;
-use crate::core::var::AlphaVar;
+use crate::core::var::{AlphaVar, Shift, Subst};
 use crate::error::{Error, ImportError, TypeError, TypeMessage};
 
 use resolve::ImportRoot;
@@ -168,26 +168,6 @@ impl Typed {
             Typed::Const(c) => Ok(Cow::Owned(type_of_const(*c)?)),
         }
     }
-
-    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
-        match self {
-            Typed::Value(th, t) => Typed::Value(
-                th.shift(delta, var),
-                t.as_ref().map(|x| x.shift(delta, var)),
-            ),
-            Typed::Const(c) => Typed::Const(*c),
-        }
-    }
-
-    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
-        match self {
-            Typed::Value(th, t) => Typed::Value(
-                th.subst_shift(var, val),
-                t.as_ref().map(|x| x.subst_shift(var, val)),
-            ),
-            Typed::Const(c) => Typed::Const(*c),
-        }
-    }
 }
 
 impl Type {
@@ -226,13 +206,6 @@ impl Type {
     pub(crate) fn from_const(c: Const) -> Self {
         Type(Box::new(Typed::from_const(c)))
     }
-
-    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
-        Type(Box::new(self.0.shift(delta, var)))
-    }
-    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
-        Type(Box::new(self.0.subst_shift(var, val)))
-    }
 }
 
 impl Normalized {
@@ -259,12 +232,50 @@ impl Normalized {
     pub(crate) fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
         self.0.get_type()
     }
+}
+
+impl Shift for Typed {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        match self {
+            Typed::Value(th, t) => Typed::Value(
+                th.shift(delta, var),
+                t.as_ref().map(|x| x.shift(delta, var)),
+            ),
+            Typed::Const(c) => Typed::Const(*c),
+        }
+    }
+}
+
+impl Shift for Type {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        Type(Box::new(self.0.shift(delta, var)))
+    }
+}
 
-    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+impl Shift for Normalized {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
         Normalized(self.0.shift(delta, var))
     }
 }
 
+impl Subst<Typed> for Typed {
+    fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            Typed::Value(th, t) => Typed::Value(
+                th.subst_shift(var, val),
+                t.as_ref().map(|x| x.subst_shift(var, val)),
+            ),
+            Typed::Const(c) => Typed::Const(*c),
+        }
+    }
+}
+
+impl Subst<Typed> for Type {
+    fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        Type(Box::new(self.0.subst_shift(var, val)))
+    }
+}
+
 macro_rules! derive_traits_for_wrapper_struct {
     ($ty:ident) => {
         impl std::cmp::PartialEq for $ty {
diff --git a/dhall/src/phase/normalize.rs b/dhall/src/phase/normalize.rs
index 5dfcfb6..e9fc570 100644
--- a/dhall/src/phase/normalize.rs
+++ b/dhall/src/phase/normalize.rs
@@ -5,6 +5,7 @@ use dhall_syntax::{BinOp, Builtin, ExprF, InterpolatedTextContents, Label, X};
 use crate::core::context::NormalizationContext;
 use crate::core::thunk::{Thunk, TypeThunk};
 use crate::core::value::Value;
+use crate::core::var::Subst;
 use crate::phase::{NormalizedSubExpr, ResolvedSubExpr, Typed};
 
 pub(crate) type InputSubExpr = ResolvedSubExpr;
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index 32c1531..f8ee559 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -11,6 +11,7 @@ use dhall_syntax::{
 use crate::core::context::{NormalizationContext, TypecheckContext};
 use crate::core::thunk::{Thunk, TypeThunk};
 use crate::core::value::Value;
+use crate::core::var::Subst;
 use crate::error::{TypeError, TypeMessage};
 use crate::phase::{Normalized, Resolved, Type, Typed};