fix unit return for if expression

tast/tast.go

@@ -158,14 +158,14 @@ func (ie *IfExpression) TokenLiteral() string { return ie.Token.Literal }
 func (ie *IfExpression) String() string {
 	var builder strings.Builder
 
-	builder.WriteString("(if\n\t")
+	builder.WriteString(fmt.Sprintf("(if %s\n\t", ie.Condition.String()))
 	builder.WriteString(ie.Then.String())
 
 	if ie.Else != nil {
 		builder.WriteString(" else in ")
 		builder.WriteString(ie.Else.String())
 	}
-	builder.WriteString(")")
+	builder.WriteString(fmt.Sprintf(") :> %s", ie.Type().Name()))
 
 	return builder.String()
 }

test.tt

@@ -1,5 +1,5 @@
 fn main() = {
     if 3 == 3
-        in 4
-        else 3
+        { if 4 == 4 in 3 }
+    else {}
 };

ttir/emit.go

@@ -98,21 +98,27 @@ func emitExpression(expr tast.Expression) (Operand, []Instruction) {
 		// } endOfIf:
 		elseLabel := tempLabel()
 		endOfIfLabel := tempLabel()
-		dst := &Var{Value: temp()}
+		var dst Operand = &Var{Value: temp()}
 
 		condDst, instructions := emitExpression(expr.Condition)
 
 		instructions = append(instructions, &JumpIfZero{Value: condDst, Label: elseLabel})
 		thenDst, thenInstructions := emitExpression(expr.Then)
 		instructions = append(instructions, thenInstructions...)
+		if !expr.ReturnType.IsSameType(types.Unit) {
 			instructions = append(instructions, &Copy{Src: thenDst, Dst: dst}, Jump(endOfIfLabel))
+		} else {
+			dst = nil
+		}
 
 		instructions = append(instructions, Label(elseLabel))
 		if expr.Else != nil {
 			elseDst, elseInstructions := emitExpression(expr.Else)
 			instructions = append(instructions, elseInstructions...)
+			if !expr.ReturnType.IsSameType(types.Unit) {
 				instructions = append(instructions, &Copy{Src: elseDst, Dst: dst})
 			}
+		}
 		instructions = append(instructions, Label(endOfIfLabel))
 		return dst, instructions
 	}