From 837a180b092cd851b810fe8569028ade9ce8e9f3 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Fri, 13 Jul 2018 21:50:38 -0700
Subject: [PATCH] Starting work on guard arms

---
 schala-lang/src/ast.rs     | 20 ++++++++++++++++----
 schala-lang/src/parsing.rs | 12 ++++++++++--
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/schala-lang/src/ast.rs b/schala-lang/src/ast.rs
index 191997c..73ec35e 100644
--- a/schala-lang/src/ast.rs
+++ b/schala-lang/src/ast.rs
@@ -125,13 +125,25 @@ pub enum Discriminator {
 pub enum IfExpressionBody {
   SimpleConditional(Block, Option<Block>),
   SimplePatternMatch(Pattern, Block, Option<Block>),
-  GuardList(Vec<Guard>)
+  GuardList(Vec<GuardArm>)
 }
 
 #[derive(Debug, PartialEq, Clone)]
-pub struct Guard {
-  pat: Pattern,
-  body: Block,
+pub struct GuardArm {
+  pub guard: Guard,
+  pub body: Block,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum Guard {
+  Pat(Pattern),
+  HalfExpr(HalfExpr)
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct HalfExpr {
+  pub op: Option<BinOp>,
+  pub expr: ExpressionType,
 }
 
 #[derive(Debug, PartialEq, Clone)]
diff --git a/schala-lang/src/parsing.rs b/schala-lang/src/parsing.rs
index 096d002..2dde59d 100644
--- a/schala-lang/src/parsing.rs
+++ b/schala-lang/src/parsing.rs
@@ -124,7 +124,8 @@ modified_precedence_expression := ???
 conditional := block else_clause
 simple_pattern_match := pattern 'then' conditional
 else_clause := ε | 'else' block
-guard_block := '{' (guard, ',')* '}'
+guard_block := '{' (guard_arm, ',')* '}'
+guard_arm := guard '->' block
 guard := ??
 
 /* Expression - While */
@@ -701,10 +702,17 @@ impl Parser {
   });
 
   parse_method!(guard_block(&mut self) -> ParseResult<IfExpressionBody> {
-    let guards = delimited!(self, LCurlyBrace, guard, Comma, RCurlyBrace);
+    let guards = delimited!(self, LCurlyBrace, guard_arm, Comma, RCurlyBrace);
     Ok(IfExpressionBody::GuardList(guards))
   });
 
+  parse_method!(guard_arm(&mut self) -> ParseResult<GuardArm> {
+    let guard = self.guard()?;
+    expect!(self, Operator(ref c) if **c == "->");
+    let body = self.block()?;
+    Ok(GuardArm { guard, body })
+  });
+
   parse_method!(guard(&mut self) -> ParseResult<Guard> {
     unimplemented!()
   });