From c0247219514f4d92374ae8a87de516b2de469252 Mon Sep 17 00:00:00 2001
From: Turiiya <34311583+ttytm@users.noreply.github.com>
Date: Fri, 15 Mar 2024 11:31:06 +0100
Subject: [PATCH] scanner: disallow a shebang line, that is not at the top of a
 file (#21029)

---
 vlib/v/scanner/scanner.v                         | 10 ++++++++++
 vlib/v/scanner/tests/shebang_outside_vsh_err.out |  7 +++++++
 vlib/v/scanner/tests/shebang_outside_vsh_err.vv  |  5 +++++
 3 files changed, 22 insertions(+)
 create mode 100644 vlib/v/scanner/tests/shebang_outside_vsh_err.out
 create mode 100644 vlib/v/scanner/tests/shebang_outside_vsh_err.vv

diff --git a/vlib/v/scanner/scanner.v b/vlib/v/scanner/scanner.v
index d98f0aca42df79..99264fa233bc9f 100644
--- a/vlib/v/scanner/scanner.v
+++ b/vlib/v/scanner/scanner.v
@@ -959,6 +959,16 @@ pub fn (mut s Scanner) text_scan() token.Token {
 				if nextc == `!` {
 					// treat shebang line (#!) as a comment
 					comment := s.text[start - 1..s.pos].trim_space()
+					if s.line_nr != 1 {
+						comment_pos := token.Pos{
+							line_nr: s.line_nr - 1
+							len: comment.len
+							pos: start
+							col: s.current_column() - comment.len
+						}
+						s.error_with_pos('a shebang is only valid at the top of the file',
+							comment_pos)
+					}
 					// s.fgenln('// shebang line "$s.line_comment"')
 					return s.new_token(.comment, comment, comment.len + 2)
 				}
diff --git a/vlib/v/scanner/tests/shebang_outside_vsh_err.out b/vlib/v/scanner/tests/shebang_outside_vsh_err.out
new file mode 100644
index 00000000000000..5f35b996fb71aa
--- /dev/null
+++ b/vlib/v/scanner/tests/shebang_outside_vsh_err.out
@@ -0,0 +1,7 @@
+vlib/v/scanner/tests/shebang_outside_vsh_err.vv:3:1: error: a shebang is only valid at the top of the file
+    1 | module foo
+    2 | 
+    3 | #!/usr/bin/env -S v
+      | ^
+    4 | 
+    5 | import os
diff --git a/vlib/v/scanner/tests/shebang_outside_vsh_err.vv b/vlib/v/scanner/tests/shebang_outside_vsh_err.vv
new file mode 100644
index 00000000000000..56a44b6c236ee1
--- /dev/null
+++ b/vlib/v/scanner/tests/shebang_outside_vsh_err.vv
@@ -0,0 +1,5 @@
+module foo
+
+#!/usr/bin/env -S v
+
+import os