From de6918b8c9ea7ed04ff81b65a614c0cf8747eef3 Mon Sep 17 00:00:00 2001
From: shadowninja55 <49539636+shadowninja55@users.noreply.github.com>
Date: Wed, 14 Jul 2021 15:33:02 -0400
Subject: [PATCH] checker: fix hex literal overflow check (#10782)

---
 vlib/v/checker/check_types.v                  | 24 +++++++++++++++----
 vlib/v/checker/tests/hex_literal_overflow.out | 22 +++++++++++++----
 vlib/v/checker/tests/hex_literal_overflow.vv  |  8 +++++--
 3 files changed, 43 insertions(+), 11 deletions(-)

diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index c4760704f0..544977b915 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -493,6 +493,8 @@ pub fn (mut c Checker) string_inter_lit(mut node ast.StringInterLiteral) ast.Typ
 	return ast.string_type
 }
 
+const hex_lit_overflow_message = 'hex character literal overflows string'
+
 pub fn (mut c Checker) string_lit(mut node ast.StringLiteral) ast.Type {
 	mut idx := 0
 	for idx < node.val.len {
@@ -511,12 +513,24 @@ pub fn (mut c Checker) string_lit(mut node ast.StringLiteral) ast.Type {
 					mut hex_char_count := 0
 					for ch.is_hex_digit() {
 						hex_char_count++
-						if hex_char_count > 4 {
-							end_pos := token.Position{
-								...start_pos
-								len: idx + 1 - start_idx
+						end_pos := token.Position{
+							...start_pos
+							len: idx + 1 - start_idx
+						}
+						match hex_char_count {
+							1...5 {}
+							6 {
+								first_digit := node.val[idx - 5] - 48
+								second_digit := node.val[idx - 4] - 48
+								if first_digit > 1 {
+									c.error(checker.hex_lit_overflow_message, end_pos)
+								} else if first_digit == 1 && second_digit > 0 {
+									c.error(checker.hex_lit_overflow_message, end_pos)
+								}
+							}
+							else {
+								c.error(checker.hex_lit_overflow_message, end_pos)
 							}
-							c.error('hex character literal overflows string', end_pos)
 						}
 						idx++
 						ch = node.val[idx] or { return ast.string_type }
diff --git a/vlib/v/checker/tests/hex_literal_overflow.out b/vlib/v/checker/tests/hex_literal_overflow.out
index b6f54ad21f..9475150399 100644
--- a/vlib/v/checker/tests/hex_literal_overflow.out
+++ b/vlib/v/checker/tests/hex_literal_overflow.out
@@ -1,4 +1,18 @@
-vlib/v/checker/tests/hex_literal_overflow.vv:1:35: error: hex character literal overflows string
-    1 | s := 'this hex character literal, \xffffffff, should be caught by the checker'
-      |                                   ~~~~~~~
-    2 | println(s)
+vlib/v/checker/tests/hex_literal_overflow.vv:1:7: error: hex character literal overflows string
+    1 | a := '\x11ffff'
+      |       ~~~~~~~~
+    2 | b := '\x20ffff'
+    3 | c := '\x10fffff'
+vlib/v/checker/tests/hex_literal_overflow.vv:2:7: error: hex character literal overflows string
+    1 | a := '\x11ffff'
+    2 | b := '\x20ffff'
+      |       ~~~~~~~~
+    3 | c := '\x10fffff'
+    4 | println(a)
+vlib/v/checker/tests/hex_literal_overflow.vv:3:7: error: hex character literal overflows string
+    1 | a := '\x11ffff'
+    2 | b := '\x20ffff'
+    3 | c := '\x10fffff'
+      |       ~~~~~~~~~
+    4 | println(a)
+    5 | println(b)
diff --git a/vlib/v/checker/tests/hex_literal_overflow.vv b/vlib/v/checker/tests/hex_literal_overflow.vv
index 3b1faaaea0..60903f8040 100644
--- a/vlib/v/checker/tests/hex_literal_overflow.vv
+++ b/vlib/v/checker/tests/hex_literal_overflow.vv
@@ -1,2 +1,6 @@
-s := 'this hex character literal, \xffffffff, should be caught by the checker'
-println(s)
+a := '\x11ffff'
+b := '\x20ffff'
+c := '\x10fffff'
+println(a)
+println(b)
+println(c)