From f2dce3864789168562101abaa84f4c074f2ad5a2 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Tue, 19 Jun 2018 02:05:25 -0700
Subject: [PATCH] Broken, but compiling, move to new if paradigm

---
 schala-lang/src/ast.rs         | 27 +++++++++++++++++++-
 schala-lang/src/parsing.rs     | 45 ++++++++++++++++++++++++++++------
 schala-lang/src/reduced_ast.rs | 12 ++++++++-
 3 files changed, 75 insertions(+), 9 deletions(-)

diff --git a/schala-lang/src/ast.rs b/schala-lang/src/ast.rs
index afbb1be..f01258f 100644
--- a/schala-lang/src/ast.rs
+++ b/schala-lang/src/ast.rs
@@ -93,7 +93,10 @@ pub enum ExpressionType {
     indexee: Box<Expression>,
     indexers: Vec<Expression>,
   },
-  IfExpression(Box<Expression>, Block, Option<Block>),
+  IfExpression {
+    discriminator: Box<Discriminator>,
+    body: Box<IfExpressionBody>,
+  },
   WhileExpression {
     condition: Option<Box<Expression>>,
     body: Block,
@@ -108,6 +111,28 @@ pub enum ExpressionType {
   },
   ListLiteral(Vec<Expression>),
 }
+#[derive(Debug, PartialEq, Clone)]
+pub enum Discriminator {
+  Simple(Expression),
+  BinOp(Expression, BinOp)
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum IfExpressionBody {
+  SimpleConditional(Block, Option<Block>),
+  GuardList(Vec<Guard>)
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct Guard {
+  pat: Pattern,
+  body: Block,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct Pattern {
+
+}
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct Enumerator {
diff --git a/schala-lang/src/parsing.rs b/schala-lang/src/parsing.rs
index 0f9a79c..aadc90a 100644
--- a/schala-lang/src/parsing.rs
+++ b/schala-lang/src/parsing.rs
@@ -97,6 +97,8 @@ int_literal = ('0x' | '0b') digits
 float_literal := digits ('.' digits)
 digits := (DIGIT_GROUP underscore)+
 
+/* OLD OBSOLETE */
+
 /* Expression - If */
 if_expr := 'if' expression block else_clause
 else_clause := ε | 'else' block
@@ -107,6 +109,13 @@ match_body := '{' (match_arm)* '}'
 match_arm := pattern '=>' expression
 pattern := identifier //TODO NOT DONE
 
+/* NEW GOOD */
+
+/* Expression - If */
+if_expr := 'if' discriminator ('then' condititional | guard_block)
+discriminator := modified_precedence_expression
+conditional := block else_clause
+else_clause := ε | 'else' block
 
 /* Expression - While */
 while_expr := 'while' while_cond '{' (statement delimiter)* '}'
@@ -618,15 +627,35 @@ impl Parser {
 
   parse_method!(if_expr(&mut self) -> ParseResult<Expression> {
     expect!(self, Keyword(Kw::If));
-    let condition = {
+    let discriminator = Box::new({
       self.restrictions.no_struct_literal = true;
-      let x = self.expression();
+      let x = self.discriminator();
       self.restrictions.no_struct_literal = false;
       x?
-    };
-    let then_clause = self.block()?;
+    });
+
+    let body = Box::new(if let Keyword(Kw::Then) = self.peek() {
+      self.conditional()?
+    } else {
+      self.guard_block()?
+    });
+
+    Ok(Expression(ExpressionType::IfExpression { discriminator, body }, None))
+  });
+
+  parse_method!(discriminator(&mut self) -> ParseResult<Discriminator> {
+    Ok(Discriminator::Simple(self.expression()?)) //TODO make proper
+  });
+
+  parse_method!(conditional(&mut self) -> ParseResult<IfExpressionBody> {
+    expect!(self, Keyword(Kw::Then));
+    let then_clause = self.block()?; //TODO should be block_or_expr
     let else_clause = self.else_clause()?;
-    Ok(Expression(ExpressionType::IfExpression(bx!(condition), then_clause, else_clause), None))
+    Ok(IfExpressionBody::SimpleConditional(then_clause, else_clause))
+  });
+
+  parse_method!(guard_block(&mut self) -> ParseResult<IfExpressionBody> {
+    ParseError::new("Rest of if not done")
   });
 
   parse_method!(else_clause(&mut self) -> ParseResult<Option<Block>> {
@@ -1094,13 +1123,14 @@ fn a(x) {
 
   #[test]
   fn parsing_block_expressions() {
-    parse_test!("if a() { b(); c() }", AST(vec![exprstatement!(
+    /*
+    parse_test!("if a() then { b(); c() }", AST(vec![exprstatement!(
         IfExpression(bx!(ex!(Call { f: bx!(ex!(val!("a"))), arguments: vec![]})),
           vec![exprstatement!(Call { f: bx!(ex!(val!("b"))), arguments: vec![]}), exprstatement!(Call { f: bx!(ex!(val!("c"))), arguments: vec![] })],
           None)
         )]));
     parse_test!(r#"
-    if true {
+    if true then {
       const a = 10
       b
     } else {
@@ -1123,6 +1153,7 @@ fn a(x) {
             Some(vec![exprstatement!(val!("c"))])))]));
 
     parse_error!("if A {a: 1} { b } else { c }");
+    */
   }
   #[test]
   fn parsing_interfaces() {
diff --git a/schala-lang/src/reduced_ast.rs b/schala-lang/src/reduced_ast.rs
index 118ea08..62ff25e 100644
--- a/schala-lang/src/reduced_ast.rs
+++ b/schala-lang/src/reduced_ast.rs
@@ -1,6 +1,6 @@
 use std::rc::Rc;
 
-use ast::{AST, Statement, Expression, Declaration};
+use ast::{AST, Statement, Expression, Declaration, Discriminator};
 use symbol_table::{Symbol, SymbolSpec, SymbolTable};
 use builtin::{BinOp, PrefixOp};
 
@@ -112,6 +112,15 @@ impl Expression {
         args: arguments.iter().map(|arg| arg.reduce(symbol_table)).collect(),
       },
       TupleLiteral(exprs) => Expr::Tuple(exprs.iter().map(|e| e.reduce(symbol_table)).collect()),
+      IfExpression { discriminator, body } => {
+        let cond = Box::new(match **discriminator {
+          Discriminator::Simple(ref expr) => expr.reduce(symbol_table),
+          _ => panic!(),
+        });
+
+        Expr::Conditional { cond, then_clause: vec![], else_clause: vec![] }
+      },
+      /*
       IfExpression(cond, then_clause, else_clause) => Expr::Conditional {
         cond: Box::new((**cond).reduce(symbol_table)),
         then_clause: then_clause.iter().map(|expr| expr.reduce(symbol_table)).collect(),
@@ -120,6 +129,7 @@ impl Expression {
           Some(stmts) => stmts.iter().map(|expr| expr.reduce(symbol_table)).collect(),
         }
       },
+      */
       _ => Expr::UnimplementedSigilValue,
     }
   }