parser: register selective import aliases as used (#21613)

vlib/v/parser/module.v

@@ -33,6 +33,12 @@ fn (mut p Parser) register_used_import(alias string) {
 
 fn (mut p Parser) register_used_import_for_symbol_name(sym_name string) {
 	short_import_name := sym_name.all_before_last('.').all_after_last('.')
+	for alias, mod in p.imports {
+		if mod == short_import_name {
+			p.register_used_import(alias)
+			return
+		}
+	}
 	p.register_used_import(short_import_name)
 }
 

vlib/v/parser/tests/import_alias_selective_fn_used.vv

@@ -0,0 +1,3 @@
+import os as vos { execute }
+
+execute('ls')

vlib/v/parser/tests/import_alias_selective_symbol_used.out

@@ -0,0 +1,5 @@
+vlib/v/parser/tests/import_alias_selective_symbol_used.vv:3:1: warning: unused variable: `os`
+    1 | import os as vos { Result }
+    2 | 
+    3 | os := Result{}
+      | ~~

vlib/v/parser/tests/import_alias_selective_symbol_used.vv

@@ -0,0 +1,3 @@
+import os as vos { Result }
+
+os := Result{}