From 7b212b2e737e9d59655a6ed5e0c344bc9254ba38 Mon Sep 17 00:00:00 2001
From: Jose Mendoza <56417208+StunxFS@users.noreply.github.com>
Date: Tue, 15 Oct 2024 15:07:06 -0400
Subject: [PATCH] checker: disallow C/JS functions and structs to be declared
 as generic (#22533)

---
 vlib/v/checker/fn.v                           |  4 +++
 vlib/v/checker/struct.v                       |  4 +++
 .../c_js_struct_and_fn_as_generics_error.out  | 26 +++++++++++++++++++
 .../c_js_struct_and_fn_as_generics_error.vv   | 13 ++++++++++
 4 files changed, 47 insertions(+)
 create mode 100644 vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.out
 create mode 100644 vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv

diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 0d04e189c..738a152cc 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -13,6 +13,10 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 			eprintln('>>> post processing node.name: ${node.name:-30} | ${node.generic_names} <=> ${c.table.cur_concrete_types}')
 		}
 	}
+	if node.language in [.c, .js] && node.generic_names.len > 0 {
+		lang := if node.language == .c { 'C' } else { 'JS' }
+		c.error('${lang} functions cannot be declared as generic', node.pos)
+	}
 	// record the veb route methods (public non-generic methods):
 	if node.generic_names.len > 0 && node.is_pub {
 		typ_vweb_result := c.table.find_type_idx('veb.Result')
diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 613a56514..22dc5d334 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -11,6 +11,10 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 	defer {
 		util.timing_measure_cumulative(@METHOD)
 	}
+	if node.language in [.c, .js] && node.generic_types.len > 0 {
+		lang := if node.language == .c { 'C' } else { 'JS' }
+		c.error('${lang} structs cannot be declared as generic', node.pos)
+	}
 	node_name := if node.scoped_name != '' { node.scoped_name } else { node.name }
 	mut struct_sym, struct_typ_idx := c.table.find_sym_and_type_idx(node_name)
 	mut has_generic_types := false
diff --git a/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.out b/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.out
new file mode 100644
index 000000000..510aa255f
--- /dev/null
+++ b/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.out
@@ -0,0 +1,26 @@
+vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv:1:1: error: C structs cannot be declared as generic
+    1 | struct C.Ptr[T] {
+      | ~~~~~~~~~~~~
+    2 |     ptr &T
+    3 | }
+vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv:5:1: error: C functions cannot be declared as generic
+    3 | }
+    4 | 
+    5 | fn C.alloc[T]() &T
+      | ~~~~~~~~~~~~~~~~~~
+    6 | 
+    7 | fn JS.encode[T](data string) T
+vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv:7:1: error: JS functions cannot be declared as generic
+    5 | fn C.alloc[T]() &T
+    6 | 
+    7 | fn JS.encode[T](data string) T
+      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    8 | 
+    9 | struct JS.Some[T] {
+vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv:9:1: error: JS structs cannot be declared as generic
+    7 | fn JS.encode[T](data string) T
+    8 | 
+    9 | struct JS.Some[T] {
+      | ~~~~~~~~~~~~~~
+   10 |     i T
+   11 | }
diff --git a/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv b/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv
new file mode 100644
index 000000000..910d99225
--- /dev/null
+++ b/vlib/v/checker/tests/c_js_struct_and_fn_as_generics_error.vv
@@ -0,0 +1,13 @@
+struct C.Ptr[T] {
+	ptr &T
+}
+
+fn C.alloc[T]() &T
+
+fn JS.encode[T](data string) T
+
+struct JS.Some[T] {
+	i T
+}
+
+fn main() {}
-- 
2.39.5