From fe212a5a339ec6fe69cd8ece4812930755be65f5 Mon Sep 17 00:00:00 2001
From: mathis2003 <49711425+mathis2003@users.noreply.github.com>
Date: Mon, 15 Mar 2021 16:55:35 +0100
Subject: [PATCH] Forced parentheses on unclear precedence (#109)

forced parentheses to resolve issue #97
---
 src/compiler/parse_expr.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/compiler/parse_expr.c b/src/compiler/parse_expr.c
index ffebdcd4c..b1de6033d 100644
--- a/src/compiler/parse_expr.c
+++ b/src/compiler/parse_expr.c
@@ -6,6 +6,21 @@
 #include "parser_internal.h"
 #include "bigint.h"
 
+#define BINOP_PREC_REQ_LEN 40
+int BINOP_PREC_REQ[BINOP_PREC_REQ_LEN] = {
+	// bitwise operations
+	[BINARYOP_BIT_OR] = 1,
+	[BINARYOP_BIT_XOR] = 1,
+	[BINARYOP_BIT_AND] = 1,
+	
+	// comparison operations
+	[BINARYOP_GT] = 2,
+	[BINARYOP_GE] = 2,
+	[BINARYOP_LT] = 2,
+	[BINARYOP_LE] = 2,
+	[BINARYOP_NE] = 2,
+	[BINARYOP_EQ] = 2
+};
 
 typedef Expr *(*ParseFn)(Context *context, Expr *);
 
@@ -367,6 +382,23 @@ static Expr *parse_failable(Context *context, Expr *left_side)
 	return failable;
 }
 
+
+bool plain_op_precedence(Expr *left_side, Expr * main_expr, Expr *right_side)
+{
+	int precedence_main = BINOP_PREC_REQ[main_expr->binary_expr.operator];
+	if (left_side->expr_kind == EXPR_BINARY)
+	{
+		int precedence_left = BINOP_PREC_REQ[left_side->binary_expr.operator]; 
+		return !(precedence_left && (precedence_left == precedence_main));
+	}
+	if (right_side->expr_kind == EXPR_BINARY)
+	{
+		int precedence_right = BINOP_PREC_REQ[right_side->binary_expr.operator];
+		return !(precedence_right && (precedence_right == precedence_main));
+	}
+	return true;
+}
+
 static Expr *parse_binary(Context *context, Expr *left_side)
 {
 	assert(left_side && expr_ok(left_side));
@@ -390,6 +422,13 @@ static Expr *parse_binary(Context *context, Expr *left_side)
 	expr->binary_expr.operator = binaryop_from_token(operator_type);
 	expr->binary_expr.left = left_side;
 	expr->binary_expr.right = right_side;
+	
+	// check if both sides have a binary operation where the precedence is unclear. Example: a ^ b | c
+	if (!plain_op_precedence(left_side, expr, right_side)) 
+	{
+		SEMA_TOKEN_ERROR(context->tok, "You need to add explicit parentheses.");
+	}
+	
 	expr->span.end_loc = right_side->span.end_loc;
 	return expr;
 }