From 6ed176515daa1dfd8c48f4f29c0dd2563027d23d Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Sun, 6 Oct 2024 19:06:50 +0530
Subject: [PATCH] checker: disallow blank ident in const and global decl
 (#22415)

---
 vlib/v/checker/checker.v                             | 12 ++++++++++++
 .../checker/tests/const_blank_ident_as_name_err.out  |  3 +++
 .../v/checker/tests/const_blank_ident_as_name_err.vv |  1 +
 .../tests/globals/global_blank_ident_as_name_err.out |  5 +++++
 .../tests/globals/global_blank_ident_as_name_err.vv  |  3 +++
 5 files changed, 24 insertions(+)
 create mode 100644 vlib/v/checker/tests/const_blank_ident_as_name_err.out
 create mode 100644 vlib/v/checker/tests/const_blank_ident_as_name_err.vv
 create mode 100644 vlib/v/checker/tests/globals/global_blank_ident_as_name_err.out
 create mode 100644 vlib/v/checker/tests/globals/global_blank_ident_as_name_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 968842e65..fb99b0d7c 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1776,6 +1776,14 @@ fn (mut c Checker) const_decl(mut node ast.ConstDecl) {
 			}
 			c.error('duplicate of a module name `${field.name}`', name_pos)
 		}
+		if const_name == '_' {
+			name_pos := token.Pos{
+				...field.pos
+				len: util.no_cur_mod(field.name, c.mod).len
+			}
+			c.error('cannot use `_` as a const name', name_pos)
+			return
+		}
 		c.const_names << field.name
 	}
 	for i, mut field in node.fields {
@@ -2308,6 +2316,10 @@ fn (mut c Checker) global_decl(mut node ast.GlobalDecl) {
 		if field.name in ast.global_reserved_type_names {
 			c.error('invalid use of reserved type `${field.name}` as a global name', field.pos)
 		}
+		if field.name == '_' {
+			c.error('cannot use `_` as a global name', field.pos)
+			return
+		}
 
 		if field.name in c.global_names {
 			c.error('duplicate global `${field.name}`', field.pos)
diff --git a/vlib/v/checker/tests/const_blank_ident_as_name_err.out b/vlib/v/checker/tests/const_blank_ident_as_name_err.out
new file mode 100644
index 000000000..dae1ae26f
--- /dev/null
+++ b/vlib/v/checker/tests/const_blank_ident_as_name_err.out
@@ -0,0 +1,3 @@
+vlib/v/checker/tests/const_blank_ident_as_name_err.vv:1:7: error: cannot use `_` as a const name
+    1 | const _ = 23
+      |       ^
diff --git a/vlib/v/checker/tests/const_blank_ident_as_name_err.vv b/vlib/v/checker/tests/const_blank_ident_as_name_err.vv
new file mode 100644
index 000000000..33705e140
--- /dev/null
+++ b/vlib/v/checker/tests/const_blank_ident_as_name_err.vv
@@ -0,0 +1 @@
+const _ = 23
diff --git a/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.out b/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.out
new file mode 100644
index 000000000..f50f1eb27
--- /dev/null
+++ b/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/globals/global_blank_ident_as_name_err.vv:2:5: error: cannot use `_` as a global name
+    1 | __global (
+    2 |     _ = 23
+      |     ^
+    3 | )
diff --git a/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.vv b/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.vv
new file mode 100644
index 000000000..f06128282
--- /dev/null
+++ b/vlib/v/checker/tests/globals/global_blank_ident_as_name_err.vv
@@ -0,0 +1,3 @@
+__global (
+    _ = 23
+)
-- 
2.39.5