From c52ae3b98665965a95aa7c64bac2f3b09d4e52ae Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Mon, 15 Jan 2024 18:32:34 +0800
Subject: [PATCH] parser: check non-generic interface defining generic method

---
 .../tests/generic_interface_method_decl_err.out     |  2 +-
 .../tests/generic_interface_method_decl_err.vv      |  2 +-
 vlib/v/parser/struct.v                              |  9 +++++++--
 vlib/v/parser/tests/generic_interface_decl_err.out  |  7 +++++++
 vlib/v/parser/tests/generic_interface_decl_err.vv   | 13 +++++++++++++
 5 files changed, 29 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/parser/tests/generic_interface_decl_err.out
 create mode 100644 vlib/v/parser/tests/generic_interface_decl_err.vv

diff --git a/vlib/v/checker/tests/generic_interface_method_decl_err.out b/vlib/v/checker/tests/generic_interface_method_decl_err.out
index 2a0b194312a4b8..4648e3b25a5051 100644
--- a/vlib/v/checker/tests/generic_interface_method_decl_err.out
+++ b/vlib/v/checker/tests/generic_interface_method_decl_err.out
@@ -1,5 +1,5 @@
 vlib/v/checker/tests/generic_interface_method_decl_err.vv:2:8: error: no need to add generic type names in generic interface's method
-    1 | interface Expr {
+    1 | interface Expr<R> {
     2 |     accept<R>(v Visitor<R>) R
       |           ^
     3 | }
diff --git a/vlib/v/checker/tests/generic_interface_method_decl_err.vv b/vlib/v/checker/tests/generic_interface_method_decl_err.vv
index 59e30df07f9b7d..3da9361b7f5bc1 100644
--- a/vlib/v/checker/tests/generic_interface_method_decl_err.vv
+++ b/vlib/v/checker/tests/generic_interface_method_decl_err.vv
@@ -1,4 +1,4 @@
-interface Expr {
+interface Expr<R> {
 	accept<R>(v Visitor<R>) R
 }
 
diff --git a/vlib/v/parser/struct.v b/vlib/v/parser/struct.v
index a72aac92e619ae..9a6ccf9dac7825 100644
--- a/vlib/v/parser/struct.v
+++ b/vlib/v/parser/struct.v
@@ -632,8 +632,13 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 			mut_pos = fields.len
 		}
 		if p.peek_tok.kind in [.lt, .lsbr] && p.peek_tok.is_next_to(p.tok) {
-			p.error_with_pos("no need to add generic type names in generic interface's method",
-				p.peek_tok.pos())
+			if generic_types.len == 0 {
+				p.error_with_pos('non-generic interface `${interface_name}` cannot define a generic method',
+					p.peek_tok.pos())
+			} else {
+				p.error_with_pos("no need to add generic type names in generic interface's method",
+					p.peek_tok.pos())
+			}
 			return ast.InterfaceDecl{}
 		}
 		mut comments := p.eat_comments()
diff --git a/vlib/v/parser/tests/generic_interface_decl_err.out b/vlib/v/parser/tests/generic_interface_decl_err.out
new file mode 100644
index 00000000000000..88576f9396610b
--- /dev/null
+++ b/vlib/v/parser/tests/generic_interface_decl_err.out
@@ -0,0 +1,7 @@
+vlib/v/parser/tests/generic_interface_decl_err.vv:4:6: error: non-generic interface `Abc` cannot define a generic method
+    2 |
+    3 | interface Abc {
+    4 |     test[T]()
+      |         ^
+    5 | }
+    6 |
diff --git a/vlib/v/parser/tests/generic_interface_decl_err.vv b/vlib/v/parser/tests/generic_interface_decl_err.vv
new file mode 100644
index 00000000000000..f5ae589c8bee43
--- /dev/null
+++ b/vlib/v/parser/tests/generic_interface_decl_err.vv
@@ -0,0 +1,13 @@
+module main
+
+interface Abc {
+	test[T]()
+}
+
+struct Xyz {}
+
+fn (xyz Xyz) test[T]() {}
+
+fn main() {
+	_ := Abc(Xyz{})
+}