Let locations be ranges, not just specific indexes.

src/syntax/ast.rs

@@ -1,3 +1,8 @@
+use std::fmt;
+use std::hash::Hash;
+
+use internment::ArcIntern;
+
 pub use crate::syntax::tokens::ConstantType;
 use crate::syntax::Location;
 
@@ -14,6 +19,50 @@ pub struct Program {
     pub statements: Vec<Statement>,
 }
 
+/// A Name.
+/// 
+/// This is basically a string, but annotated with the place the string
+/// is in the source file.
+#[derive(Clone, Debug)]
+pub struct Name {
+    pub name: String,
+    pub location: Location,
+}
+
+impl Name {
+    pub fn new<S: ToString>(n: S, location: Location) -> Name {
+        Name{ name: n.to_string(), location }
+    }
+
+    pub fn manufactured<S: ToString>(n: S) -> Name {
+        Name{ name: n.to_string(), location: Location::manufactured() }
+    }
+
+    pub fn intern(self) -> ArcIntern<String> {
+        ArcIntern::new(self.name)
+    }
+}
+
+impl PartialEq for Name {
+    fn eq(&self, other: &Self) -> bool {
+        self.name == other.name
+    }
+}
+
+impl Eq for Name {}
+
+impl Hash for Name {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.name.hash(state)
+    }
+}
+
+impl fmt::Display for Name {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.name.fmt(f)
+    }
+}
+
 /// A parsed statement.
 ///
 /// Statements are guaranteed to be syntactically valid, but may be
@@ -27,8 +76,8 @@ pub struct Program {
 /// thing, not if they are the exact same statement.
 #[derive(Clone, Debug)]
 pub enum Statement {
-    Binding(Location, String, Expression),
-    Print(Location, String),
+    Binding(Location, Name, Expression),
+    Print(Location, Name),
 }
 
 impl PartialEq for Statement {