From 99574e465dc88f1320b9839c7c29da7c0e419b6c Mon Sep 17 00:00:00 2001
From: Henrixounez <30901439+Henrixounez@users.noreply.github.com>
Date: Fri, 18 Sep 2020 01:02:06 +0200
Subject: [PATCH] scanner: allow escape on null character (#6404)

---
 vlib/v/checker/tests/string_char_null_err.out | 5 +++++
 vlib/v/checker/tests/string_char_null_err.vv  | 3 +++
 vlib/v/scanner/scanner.v                      | 5 +++--
 3 files changed, 11 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/checker/tests/string_char_null_err.out
 create mode 100644 vlib/v/checker/tests/string_char_null_err.vv

diff --git a/vlib/v/checker/tests/string_char_null_err.out b/vlib/v/checker/tests/string_char_null_err.out
new file mode 100644
index 0000000000..942bfd1f99
--- /dev/null
+++ b/vlib/v/checker/tests/string_char_null_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/string_char_null_err.vv:2:31: error: 0 character in a string literal
+    1 | fn main() {
+    2 |     println('Null character: \0')
+      |                               ^
+    3 | }
diff --git a/vlib/v/checker/tests/string_char_null_err.vv b/vlib/v/checker/tests/string_char_null_err.vv
new file mode 100644
index 0000000000..d60854f829
--- /dev/null
+++ b/vlib/v/checker/tests/string_char_null_err.vv
@@ -0,0 +1,3 @@
+fn main() {
+    println('Null character: \0')
+}
diff --git a/vlib/v/scanner/scanner.v b/vlib/v/scanner/scanner.v
index 5e31e6a094..02ba60d33c 100644
--- a/vlib/v/scanner/scanner.v
+++ b/vlib/v/scanner/scanner.v
@@ -1216,14 +1216,15 @@ fn (mut s Scanner) ident_string() string {
 		}
 		// Don't allow \0
 		if c == `0` && s.pos > 2 && s.text[s.pos - 1] == slash {
-			if s.pos < s.text.len - 1 && s.text[s.pos + 1].is_digit() {
+			if (s.pos < s.text.len - 1 && s.text[s.pos + 1].is_digit()) || s.count_symbol_before(s.pos - 1, slash) % 2 == 0 {
 			} else if !is_cstr {
 				s.error('0 character in a string literal')
 			}
 		}
 		// Don't allow \x00
 		if c == `0` && s.pos > 5 && s.expect('\\x0', s.pos - 3) {
-			if !is_cstr {
+			if s.count_symbol_before(s.pos - 3, slash) % 2 == 0 {
+			} else if !is_cstr {
 				s.error('0 character in a string literal')
 			}
 		}