From 55cac8841a265c57b21b025b7673c3a58f4c09dd Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Mon, 13 Nov 2023 21:42:54 +0530
Subject: [PATCH]  checker: disallow `$for i in struct.values` and `$for i in
 enum.fields` (#19845)

---
 vlib/v/checker/comptime.v                               | 8 ++++++++
 vlib/v/checker/tests/for_comptime_enum_fields_err.out   | 7 +++++++
 vlib/v/checker/tests/for_comptime_enum_fields_err.vv    | 8 ++++++++
 vlib/v/checker/tests/for_comptime_struct_values_err.out | 7 +++++++
 vlib/v/checker/tests/for_comptime_struct_values_err.vv  | 7 +++++++
 5 files changed, 37 insertions(+)
 create mode 100644 vlib/v/checker/tests/for_comptime_enum_fields_err.out
 create mode 100644 vlib/v/checker/tests/for_comptime_enum_fields_err.vv
 create mode 100644 vlib/v/checker/tests/for_comptime_struct_values_err.out
 create mode 100644 vlib/v/checker/tests/for_comptime_struct_values_err.vv

diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index fb1a98d1e..c3a55c43b 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -287,6 +287,10 @@ fn (mut c Checker) comptime_for(mut node ast.ComptimeFor) {
 			}
 			c.comptime_for_field_var = ''
 			c.inside_comptime_for_field = false
+		} else if c.table.generic_type_names(node.typ).len == 0 && sym.kind != .placeholder {
+			c.error('iterating over .fields is supported only for structs and interfaces, and ${sym.name} is neither',
+				node.typ_pos)
+			return
 		}
 	} else if node.kind == .values {
 		if sym.kind == .enum_ {
@@ -301,6 +305,10 @@ fn (mut c Checker) comptime_for(mut node ast.ComptimeFor) {
 				c.comptime_fields_type[node.val_var] = node.typ
 				c.stmts(mut node.stmts)
 			}
+		} else {
+			c.error('iterating over .values is supported only for enums, and ${sym.name} is not an enum',
+				node.typ_pos)
+			return
 		}
 	} else {
 		c.stmts(mut node.stmts)
diff --git a/vlib/v/checker/tests/for_comptime_enum_fields_err.out b/vlib/v/checker/tests/for_comptime_enum_fields_err.out
new file mode 100644
index 000000000..8c99aab27
--- /dev/null
+++ b/vlib/v/checker/tests/for_comptime_enum_fields_err.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/for_comptime_enum_fields_err.vv:6:11: error: iterating over .fields is supported only for structs and interfaces, and Test is neither
+    4 | }
+    5 | 
+    6 | $for i in Test.fields {
+      |           ~~~~
+    7 |     println(i)
+    8 | }
diff --git a/vlib/v/checker/tests/for_comptime_enum_fields_err.vv b/vlib/v/checker/tests/for_comptime_enum_fields_err.vv
new file mode 100644
index 000000000..07b90cf3b
--- /dev/null
+++ b/vlib/v/checker/tests/for_comptime_enum_fields_err.vv
@@ -0,0 +1,8 @@
+enum Test {
+	one
+	two
+}
+
+$for i in Test.fields {
+	println(i)
+}
diff --git a/vlib/v/checker/tests/for_comptime_struct_values_err.out b/vlib/v/checker/tests/for_comptime_struct_values_err.out
new file mode 100644
index 000000000..8502ca049
--- /dev/null
+++ b/vlib/v/checker/tests/for_comptime_struct_values_err.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/for_comptime_struct_values_err.vv:5:11: error: iterating over .values is supported only for enums, and Foo is not an enum
+    3 | fn (_ Foo) hello() {}
+    4 | 
+    5 | $for i in Foo.values {
+      |           ~~~
+    6 |     println(i)
+    7 | }
diff --git a/vlib/v/checker/tests/for_comptime_struct_values_err.vv b/vlib/v/checker/tests/for_comptime_struct_values_err.vv
new file mode 100644
index 000000000..e41918b2c
--- /dev/null
+++ b/vlib/v/checker/tests/for_comptime_struct_values_err.vv
@@ -0,0 +1,7 @@
+struct Foo{}
+
+fn (_ Foo) hello() {}
+
+$for i in Foo.values {
+	println(i)
+}
-- 
2.39.5