From ea3983a91b56ce3bc888cd84931756df6c3061b2 Mon Sep 17 00:00:00 2001
From: shadowninja55 <49539636+shadowninja55@users.noreply.github.com>
Date: Sun, 27 Jun 2021 10:17:03 -0400
Subject: [PATCH] checker: require .sort() body for some types (#10550)

---
 vlib/v/checker/checker.v                      |  4 ++++
 .../tests/array_sort_struct_no_body_err.out   |  5 +++++
 .../tests/array_sort_struct_no_body_err.vv    |  6 +++++
 vlib/v/tests/array_sort_lt_overload_test.v    | 22 +++++++++++++++++++
 4 files changed, 37 insertions(+)
 create mode 100644 vlib/v/checker/tests/array_sort_struct_no_body_err.out
 create mode 100644 vlib/v/checker/tests/array_sort_struct_no_body_err.vv
 create mode 100644 vlib/v/tests/array_sort_lt_overload_test.v

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index c7dfd7ce7..9b7693853 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2196,6 +2196,10 @@ fn (mut c Checker) array_builtin_method_call(mut call_expr ast.CallExpr, left_ty
 					'`.sort()` requires a `<` or `>` comparison as the first and only argument' +
 					'\ne.g. `users.sort(a.id < b.id)`', call_expr.pos)
 			}
+		} else if !(c.table.get_type_symbol(elem_typ).has_method('<')
+			|| c.table.unalias_num_type(elem_typ) in [ast.int_type, ast.int_type.to_ptr(), ast.string_type, ast.string_type.to_ptr(), ast.i8_type, ast.i16_type, ast.i64_type, ast.byte_type, ast.rune_type, ast.u16_type, ast.u32_type, ast.u64_type, ast.f32_type, ast.f64_type, ast.char_type, ast.bool_type, ast.float_literal_type, ast.int_literal_type, ast.size_t_type_idx]) {
+			c.error('custom sorting condition must be supplied for type `${c.table.type_to_str(elem_typ)}`',
+				call_expr.pos)
 		}
 	} else if method_name == 'wait' {
 		elem_sym := c.table.get_type_symbol(elem_typ)
diff --git a/vlib/v/checker/tests/array_sort_struct_no_body_err.out b/vlib/v/checker/tests/array_sort_struct_no_body_err.out
new file mode 100644
index 000000000..dd83a0bfb
--- /dev/null
+++ b/vlib/v/checker/tests/array_sort_struct_no_body_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/array_sort_struct_no_body_err.vv:6:5: error: custom sorting condition must be supplied for type `Foo`
+    4 | 
+    5 | mut arr := []Foo{}
+    6 | arr.sort()
+      |     ~~~~~~
diff --git a/vlib/v/checker/tests/array_sort_struct_no_body_err.vv b/vlib/v/checker/tests/array_sort_struct_no_body_err.vv
new file mode 100644
index 000000000..6b53ea9e9
--- /dev/null
+++ b/vlib/v/checker/tests/array_sort_struct_no_body_err.vv
@@ -0,0 +1,6 @@
+struct Foo {
+	bar int
+}
+
+mut arr := []Foo{}
+arr.sort()
diff --git a/vlib/v/tests/array_sort_lt_overload_test.v b/vlib/v/tests/array_sort_lt_overload_test.v
new file mode 100644
index 000000000..b37f022bf
--- /dev/null
+++ b/vlib/v/tests/array_sort_lt_overload_test.v
@@ -0,0 +1,22 @@
+struct Num {
+	value int
+}
+
+fn (a Num) < (b Num) bool {
+	return a.value < b.value
+}
+
+fn test_sort_lt_overloaded_struct_array() {
+	mut arr := []Num{}
+	arr << {
+		value: 10
+	}
+	arr << {
+		value: 5
+	}
+	arr << {
+		value: 7
+	}
+	arr.sort()
+	assert arr[0].value == 5
+}
-- 
2.39.5