From a6eb2b402098a1ec54aa97d2859af1cd82d04439 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Wed, 20 Feb 2019 22:44:45 -0800
Subject: [PATCH] Allow type annotations in let expressions

---
 schala-lang/language/src/ast.rs         |  1 +
 schala-lang/language/src/parsing.rs     | 18 ++++++++++++++----
 schala-lang/language/src/reduced_ast.rs |  2 +-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/schala-lang/language/src/ast.rs b/schala-lang/language/src/ast.rs
index 05fad6e..112026f 100644
--- a/schala-lang/language/src/ast.rs
+++ b/schala-lang/language/src/ast.rs
@@ -56,6 +56,7 @@ pub enum Declaration {
   Binding {
     name: Rc<String>,
     constant: bool,
+    type_anno: Option<TypeIdentifier>,
     expr: Expression,
   },
   Impl {
diff --git a/schala-lang/language/src/parsing.rs b/schala-lang/language/src/parsing.rs
index bc96350..408d42a 100644
--- a/schala-lang/language/src/parsing.rs
+++ b/schala-lang/language/src/parsing.rs
@@ -444,10 +444,16 @@ impl Parser {
       _ => true
     };
     let name = self.identifier()?;
+    let type_anno = if let Colon = self.token_handler.peek_kind() {
+      Some(self.type_anno()?)
+    } else {
+      None
+    };
+
     expect!(self, Operator(ref o) if **o == "=");
     let expr = self.expression()?;
 
-    Ok(Declaration::Binding { name, constant, expr })
+    Ok(Declaration::Binding { name, constant, type_anno, expr })
   }
 
   #[recursive_descent_method]
@@ -1368,8 +1374,12 @@ fn a(x) {
 
   #[test]
   fn parsing_bindings() {
-    parse_test!("let mut a = 10", AST(vec![Node::new(Declaration(Binding { name: rc!(a), constant: false, expr: ex!(NatLiteral(10)) } ))]));
-    parse_test!("let a = 2 + 2", AST(vec![Node::new(Declaration(Binding { name: rc!(a), constant: true, expr: ex!(binexp!("+", NatLiteral(2), NatLiteral(2))) }) )]));
+    parse_test!("let mut a = 10", AST(vec![Node::new(Declaration(Binding { name: rc!(a), constant: false, type_anno: None, expr: ex!(NatLiteral(10)) } ))]));
+    parse_test!("let a = 2 + 2", AST(vec![Node::new(Declaration(Binding { name: rc!(a), constant: true, type_anno: None, expr: ex!(binexp!("+", NatLiteral(2), NatLiteral(2))) }) )]));
+    parse_test!("let a: Nat = 2 + 2", AST(vec![Node::new(Declaration(
+      Binding { name: rc!(a), constant: true, type_anno: Some(Singleton(TypeSingletonName { name: rc!(Nat), params: vec![] })),
+      expr: ex!(binexp!("+", NatLiteral(2), NatLiteral(2))) }
+    ))]));
   }
 
   #[test]
@@ -1497,7 +1507,7 @@ fn a(x) {
   fn parsing_type_annotations() {
     parse_test!("let a = b : Int", AST(vec![
       Node::new(
-      Declaration(Binding { name: rc!(a), constant: true, expr:
+      Declaration(Binding { name: rc!(a), constant: true, type_anno: None, expr:
         Expression(val!("b"), Some(ty!("Int"))) }))]));
 
     parse_test!("a : Int", AST(vec![
diff --git a/schala-lang/language/src/reduced_ast.rs b/schala-lang/language/src/reduced_ast.rs
index 5b164c8..b6b1dc4 100644
--- a/schala-lang/language/src/reduced_ast.rs
+++ b/schala-lang/language/src/reduced_ast.rs
@@ -358,7 +358,7 @@ impl Declaration {
     use self::Declaration::*;
     use crate::ast::Signature;
     match self {
-      Binding {name, constant, expr } => Stmt::Binding { name: name.clone(), constant: *constant, expr: expr.reduce(symbol_table) },
+      Binding {name, constant, expr, .. } => Stmt::Binding { name: name.clone(), constant: *constant, expr: expr.reduce(symbol_table) },
       FuncDecl(Signature { name, params, .. }, statements) => Stmt::PreBinding {
         name: name.clone(),
         func: Func::UserDefined {