From 915ab53b3ca3ff97ab8f70ee77c2aee2cafb2218 Mon Sep 17 00:00:00 2001
From: Swastik <swstkbaranwal@gmail.com>
Date: Mon, 30 Sep 2024 00:24:28 +0530
Subject: [PATCH] checker: disallow invalid `T` cast

---
 vlib/v/checker/checker.v                      |  6 +++++
 .../tests/globals/cast_expr_T_type_err.out    | 14 ++++++++++++
 .../tests/globals/cast_expr_T_type_err.vv     | 22 +++++++++++++++++++
 3 files changed, 42 insertions(+)
 create mode 100644 vlib/v/checker/tests/globals/cast_expr_T_type_err.out
 create mode 100644 vlib/v/checker/tests/globals/cast_expr_T_type_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 7a73c1a680130d..3022740d3b15a1 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3191,6 +3191,12 @@ fn (mut c Checker) cast_expr(mut node ast.CastExpr) ast.Type {
 		return to_type
 	}
 
+	type_str := c.table.type_to_str(to_type)
+	type_rm_ptr := type_str.replace('&', '')
+	if type_rm_ptr.len == 1 && type_rm_ptr.starts_with_capital() {
+		c.error('unknown type `${to_sym.name}`', node.pos)
+	}
+
 	if to_sym.language != .c {
 		c.ensure_type_exists(to_type, node.pos)
 
diff --git a/vlib/v/checker/tests/globals/cast_expr_T_type_err.out b/vlib/v/checker/tests/globals/cast_expr_T_type_err.out
new file mode 100644
index 00000000000000..1ddaafab2666f7
--- /dev/null
+++ b/vlib/v/checker/tests/globals/cast_expr_T_type_err.out
@@ -0,0 +1,14 @@
+vlib/v/checker/tests/globals/cast_expr_T_type_err.vv:4:7: error: unknown type `A`
+    2 | 
+    3 | __global (
+    4 |     fo = A(0)
+      |          ~~~~
+    5 |     fo1 = &A(0)
+    6 | )
+vlib/v/checker/tests/globals/cast_expr_T_type_err.vv:5:8: error: unknown type `A`
+    3 | __global (
+    4 |     fo = A(0)
+    5 |     fo1 = &A(0)
+      |           ~~~~~
+    6 | )
+    7 |
diff --git a/vlib/v/checker/tests/globals/cast_expr_T_type_err.vv b/vlib/v/checker/tests/globals/cast_expr_T_type_err.vv
new file mode 100644
index 00000000000000..cd2f9c3f445724
--- /dev/null
+++ b/vlib/v/checker/tests/globals/cast_expr_T_type_err.vv
@@ -0,0 +1,22 @@
+module main
+
+__global (
+	fo = A(0)
+	fo1 = &A(0)
+)
+
+fn main() {
+
+}
+
+module main
+
+__global (
+	fo = A(0)
+	fo1 = &A(0)
+)
+
+fn main() {
+
+}
+