From ddb2e72301444663856aaa33eae81414fc037ece Mon Sep 17 00:00:00 2001
From: "Caian R. Ertl" <hi@caian.org>
Date: Fri, 9 Apr 2021 07:14:27 -0300
Subject: [PATCH] checker: do not allow module aliases started with '_'
 (underscore) (#9588)

---
 vlib/v/checker/checker.v                                   | 1 +
 .../tests/modules/module_alias_started_with_underscore.out | 7 +++++++
 .../modules/module_alias_started_with_underscore/main.v    | 7 +++++++
 .../module_alias_started_with_underscore/underscore.v      | 5 +++++
 4 files changed, 20 insertions(+)
 create mode 100644 vlib/v/checker/tests/modules/module_alias_started_with_underscore.out
 create mode 100644 vlib/v/checker/tests/modules/module_alias_started_with_underscore/main.v
 create mode 100644 vlib/v/checker/tests/modules/module_alias_started_with_underscore/underscore.v

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 84ee4087c8..1680435cb3 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3977,6 +3977,7 @@ fn (mut c Checker) hash_stmt(mut node ast.HashStmt) {
 }
 
 fn (mut c Checker) import_stmt(imp ast.Import) {
+	c.check_valid_snake_case(imp.alias, 'module alias', imp.pos)
 	for sym in imp.syms {
 		name := '${imp.mod}.$sym.name'
 		if sym.name[0].is_capital() {
diff --git a/vlib/v/checker/tests/modules/module_alias_started_with_underscore.out b/vlib/v/checker/tests/modules/module_alias_started_with_underscore.out
new file mode 100644
index 0000000000..a0cc315c1b
--- /dev/null
+++ b/vlib/v/checker/tests/modules/module_alias_started_with_underscore.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/modules/module_alias_started_with_underscore/main.v:3:1: error: module alias `_` cannot start with `_`
+    1 | module main
+    2 | 
+    3 | import underscore as _
+      | ~~~~~~~~~~~~~~~~~~~~~~
+    4 | 
+    5 | fn main() {
diff --git a/vlib/v/checker/tests/modules/module_alias_started_with_underscore/main.v b/vlib/v/checker/tests/modules/module_alias_started_with_underscore/main.v
new file mode 100644
index 0000000000..39f80a1cfb
--- /dev/null
+++ b/vlib/v/checker/tests/modules/module_alias_started_with_underscore/main.v
@@ -0,0 +1,7 @@
+module main
+
+import underscore as _
+
+fn main() {
+	_.foo()
+}
diff --git a/vlib/v/checker/tests/modules/module_alias_started_with_underscore/underscore.v b/vlib/v/checker/tests/modules/module_alias_started_with_underscore/underscore.v
new file mode 100644
index 0000000000..ec83c1ca7a
--- /dev/null
+++ b/vlib/v/checker/tests/modules/module_alias_started_with_underscore/underscore.v
@@ -0,0 +1,5 @@
+module underscore
+
+pub fn foo() {
+	println('bar')
+}