parser: disallow generic function to be exported (fix #25794) (#25806)

Author: Delta456

vlib/v/parser/fn.v

@@ -473,6 +473,14 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 			}
 		}
 	}
+	if generic_names.len > 0 {
+		for fna in fn_attrs {
+			if fna.name == 'export' {
+				p.error_with_pos('generic functions cannot be exported', fna.pos)
+				break
+			}
+		}
+	}
 	// Params
 	params_t, are_params_type_only, mut is_variadic, mut is_c_variadic := p.fn_params()
 	if is_c2v_variadic {

vlib/v/parser/tests/generic_fn_export_err.out

@@ -0,0 +1,5 @@
+vlib/v/parser/tests/generic_fn_export_err.vv:1:1: error: generic functions cannot be exported
+    1 | @[export: "sort_array"]
+      | ~~~~~~~~~~~~~~~~~~~~~~~
+    2 | pub fn sort_array[T](mut arr []T) {
+    3 |     arr.sort(|a, b| a < b)

vlib/v/parser/tests/generic_fn_export_err.vv

@@ -0,0 +1,4 @@
+@[export: "sort_array"]
+pub fn sort_array[T](mut arr []T) {
+	arr.sort(|a, b| a < b)
+}