From 44c78ed761c0d295db470b3e3552c5049294c829 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Wed, 20 Mar 2024 01:12:37 +0530
Subject: [PATCH]  parser: add better error for mut variadic fn argument 
 (#21063)

---
 vlib/v/parser/fn.v                                    | 8 ++++++++
 vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.out | 3 +++
 vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv  | 1 +
 vlib/v/parser/tests/fn_arg_variadic_mut_err.out       | 5 +++++
 vlib/v/parser/tests/fn_arg_variadic_mut_err.vv        | 3 +++
 5 files changed, 20 insertions(+)
 create mode 100644 vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.out
 create mode 100644 vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv
 create mode 100644 vlib/v/parser/tests/fn_arg_variadic_mut_err.out
 create mode 100644 vlib/v/parser/tests/fn_arg_variadic_mut_err.vv

diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index eb7e3da52..2e2689964 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -912,6 +912,10 @@ fn (mut p Parser) fn_params() ([]ast.Param, bool, bool) {
 			}
 			if is_mut {
 				if !param_type.has_flag(.generic) {
+					if is_variadic {
+						p.error_with_pos('variadic arguments cannot be `mut`, `shared` or `atomic`',
+							pos)
+					}
 					if is_shared {
 						p.check_fn_shared_arguments(param_type, pos)
 					} else if is_atomic {
@@ -1027,6 +1031,10 @@ fn (mut p Parser) fn_params() ([]ast.Param, bool, bool) {
 			}
 			if is_mut {
 				if !typ.has_flag(.generic) {
+					if is_variadic {
+						p.error_with_pos('variadic arguments cannot be `mut`, `shared` or `atomic`',
+							pos)
+					}
 					if is_shared {
 						p.check_fn_shared_arguments(typ, pos)
 					} else if is_atomic {
diff --git a/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.out b/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.out
new file mode 100644
index 000000000..2711016b3
--- /dev/null
+++ b/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.out
@@ -0,0 +1,3 @@
+vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv:1:22: error: variadic arguments cannot be `mut`, `shared` or `atomic`
+    1 | type Foo = fn(mut ...string)
+      |                      ~~~~~~
diff --git a/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv b/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv
new file mode 100644
index 000000000..602647041
--- /dev/null
+++ b/vlib/v/parser/tests/fn_alias_arg_variadic_mut_err.vv
@@ -0,0 +1 @@
+type Foo = fn(mut ...string)
diff --git a/vlib/v/parser/tests/fn_arg_variadic_mut_err.out b/vlib/v/parser/tests/fn_arg_variadic_mut_err.out
new file mode 100644
index 000000000..3a8a4ad05
--- /dev/null
+++ b/vlib/v/parser/tests/fn_arg_variadic_mut_err.out
@@ -0,0 +1,5 @@
+vlib/v/parser/tests/fn_arg_variadic_mut_err.vv:1:26: error: variadic arguments cannot be `mut`, `shared` or `atomic`
+    1 | fn load(mut filepaths ...string) {
+      |                          ~~~~~~
+    2 |     println(filepaths[0])
+    3 | }
diff --git a/vlib/v/parser/tests/fn_arg_variadic_mut_err.vv b/vlib/v/parser/tests/fn_arg_variadic_mut_err.vv
new file mode 100644
index 000000000..bef98a0db
--- /dev/null
+++ b/vlib/v/parser/tests/fn_arg_variadic_mut_err.vv
@@ -0,0 +1,3 @@
+fn load(mut filepaths ...string) {
+	println(filepaths[0])
+}
-- 
2.39.5