From 7fd08eca9661654dab93b5fdb4f420e772d85a09 Mon Sep 17 00:00:00 2001
From: skurgs <73891182+skurgs@users.noreply.github.com>
Date: Mon, 24 Jan 2022 05:13:22 -0500
Subject: [PATCH] checker: fix c error on improper string to rune cast (#13197)
 (#13257)

---
 vlib/v/checker/checker.v                      |  5 ++++
 .../checker/tests/cast_string_to_rune_err.out | 26 +++++++++++++++++++
 .../checker/tests/cast_string_to_rune_err.vv  |  6 +++++
 3 files changed, 37 insertions(+)
 create mode 100644 vlib/v/checker/tests/cast_string_to_rune_err.out
 create mode 100644 vlib/v/checker/tests/cast_string_to_rune_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 14dde985dc..89de87c58f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2732,6 +2732,11 @@ pub fn (mut c Checker) cast_expr(mut node ast.CastExpr) ast.Type {
 			node.pos)
 	}
 
+	if to_sym.kind == .rune && from_sym.is_string() {
+		snexpr := node.expr.str()
+		c.error('cannot cast `$from_sym.name` to rune, use `${snexpr}.runes()` instead.', node.pos)
+	}
+
 	if to_type == ast.string_type {
 		if from_type in [ast.byte_type, ast.bool_type] {
 			snexpr := node.expr.str()
diff --git a/vlib/v/checker/tests/cast_string_to_rune_err.out b/vlib/v/checker/tests/cast_string_to_rune_err.out
new file mode 100644
index 0000000000..f64215013d
--- /dev/null
+++ b/vlib/v/checker/tests/cast_string_to_rune_err.out
@@ -0,0 +1,26 @@
+vlib/v/checker/tests/cast_string_to_rune_err.vv:2:7: error: cannot cast `string` to rune, use `'0'.runes()` instead.
+    1 | fn main() {
+    2 |     _ := rune('0')
+      |          ~~~~~~~~~
+    3 |     _ := rune('012345')
+    4 |     _ := rune('v')
+vlib/v/checker/tests/cast_string_to_rune_err.vv:3:7: error: cannot cast `string` to rune, use `'012345'.runes()` instead.
+    1 | fn main() {
+    2 |     _ := rune('0')
+    3 |     _ := rune('012345')
+      |          ~~~~~~~~~~~~~~
+    4 |     _ := rune('v')
+    5 |     _ := rune('abcd')
+vlib/v/checker/tests/cast_string_to_rune_err.vv:4:7: error: cannot cast `string` to rune, use `'v'.runes()` instead.
+    2 |     _ := rune('0')
+    3 |     _ := rune('012345')
+    4 |     _ := rune('v')
+      |          ~~~~~~~~~
+    5 |     _ := rune('abcd')
+    6 | }
+vlib/v/checker/tests/cast_string_to_rune_err.vv:5:7: error: cannot cast `string` to rune, use `'abcd'.runes()` instead.
+    3 |     _ := rune('012345')
+    4 |     _ := rune('v')
+    5 |     _ := rune('abcd')
+      |          ~~~~~~~~~~~~
+    6 | }
diff --git a/vlib/v/checker/tests/cast_string_to_rune_err.vv b/vlib/v/checker/tests/cast_string_to_rune_err.vv
new file mode 100644
index 0000000000..d2ac2b5cc6
--- /dev/null
+++ b/vlib/v/checker/tests/cast_string_to_rune_err.vv
@@ -0,0 +1,6 @@
+fn main() {
+	_ := rune('0')
+	_ := rune('012345')
+	_ := rune('v')
+	_ := rune('abcd')
+}