From a7cad3b88e000dec04af27357619caaab1ef48d4 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Mon, 11 Nov 2019 02:55:00 -0800
Subject: [PATCH] Try associated type

---
 schala-lang/language/src/ast/visitor.rs      | 15 ++++++++-------
 schala-lang/language/src/ast/visitor_test.rs |  7 ++++---
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/schala-lang/language/src/ast/visitor.rs b/schala-lang/language/src/ast/visitor.rs
index dfd9ee2..c78a78f 100644
--- a/schala-lang/language/src/ast/visitor.rs
+++ b/schala-lang/language/src/ast/visitor.rs
@@ -40,15 +40,16 @@ pub trait ASTVisitor: Sized {
   fn pattern(&mut self, _pat: &Pattern) {}
 }
 
-pub trait ExpressionVisitor<T> {//TODO maybe this should be an associated type?
-  fn type_anno(&mut self, _anno: &TypeIdentifier) -> T;
-  fn nat_literal(&mut self, _value: &u64) -> T;
-  fn string_literal(&mut self, _value: &Rc<String>) -> T;
-  fn binexp(&mut self, _op: &BinOp, _lhs_resul: T, _rhs_result: T) -> T;
-  fn done(&mut self, kind: T, anno: Option<T>) -> T;
+pub trait ExpressionVisitor {//TODO maybe this should be an associated type?
+  type Output;
+  fn type_anno(&mut self, _anno: &TypeIdentifier) -> Self::Output;
+  fn nat_literal(&mut self, _value: &u64) -> Self::Output;
+  fn string_literal(&mut self, _value: &Rc<String>) -> Self::Output;
+  fn binexp(&mut self, _op: &BinOp, _lhs_resul: Self::Output, _rhs_result: Self::Output) -> Self::Output;
+  fn done(&mut self, kind: Self::Output, anno: Option<Self::Output>) -> Self::Output;
 }
 
-pub fn dispatch_expression_visitor<T>(input: &Expression, visitor: &mut dyn ExpressionVisitor<T>) -> Result<T, String> {
+pub fn dispatch_expression_visitor<T>(input: &Expression, visitor: &mut dyn ExpressionVisitor<Output=T>) -> Result<T, String> {
 
   let output = match input.kind {
     ExpressionKind::NatLiteral(ref n) => visitor.nat_literal(n),
diff --git a/schala-lang/language/src/ast/visitor_test.rs b/schala-lang/language/src/ast/visitor_test.rs
index d180d30..680c8da 100644
--- a/schala-lang/language/src/ast/visitor_test.rs
+++ b/schala-lang/language/src/ast/visitor_test.rs
@@ -45,7 +45,8 @@ fn heh() {
 struct ExprPrinter {
 }
 
-impl ExpressionVisitor<String> for ExprPrinter {
+impl ExpressionVisitor for ExprPrinter {
+  type Output = String;
   fn type_anno(&mut self, _anno: &TypeIdentifier) -> String {
     "Any".to_string()
   }
@@ -81,9 +82,9 @@ fn make_expr(input: &str) -> Expression {
 
 #[test]
 fn new_visitor() {
-  let expr: Expression = make_expr("7+20");
+  let expr: Expression = make_expr("7+\"nueces\"");
 
   let mut printer = ExprPrinter { };
   let s = dispatch_expression_visitor(&expr, &mut printer).unwrap();
-  assert_eq!(s, "7 + 20");
+  assert_eq!(s, r#"7 + "nueces""#);
 }