Basic if-statement checking

schala-lang/language/src/typechecking.rs

@@ -260,9 +260,32 @@ impl<'a> TypeContext<'a> {
   }
 
   fn if_expr(&mut self, discriminator: &Discriminator, body: &IfExpressionBody) -> InferResult<Type> {
-    //only handle simple case for now
+    use self::Discriminator::*; use self::IfExpressionBody::*;
+    match (discriminator, body) {
+      (Simple(expr), SimpleConditional(then_clause, else_clause)) => self.handle_simple_if(expr, then_clause, else_clause),
+      _ => TypeError::new(&format!("Complex conditionals not supported"))
+    }
+  }
 
-    Ok(ty!(Unit))
+  fn handle_simple_if(&mut self, expr: &Expression, then_clause: &Block, else_clause: &Option<Block>) -> InferResult<Type> {
+    let t1 = self.expr(expr)?;
+    let t2 = self.block(then_clause)?;
+    let t3 = match else_clause {
+      Some(block) => self.block(block)?,
+      None => ty!(Unit)
+    };
+
+    let _ = self.unify(ty!(Bool), t1)?;
+    self.unify(t2, t3)
+  }
+
+  fn block(&mut self, block: &Block) -> InferResult<Type> {
+    let mut output = ty!(Unit);
+    for s in block.iter() {
+      let statement = s.node();
+      output = self.statement(statement)?;
+    }
+    Ok(output)
   }
 
   fn handle_value(&mut self, val: &Rc<String>) -> InferResult<Type> {