From a94228bb16805a03ffc26725ff82f5cc1eff14e4 Mon Sep 17 00:00:00 2001
From: zakuro <z@kuro.red>
Date: Sat, 6 Feb 2021 00:49:40 +0900
Subject: [PATCH] checker: make `[] == ArrayAlias([])` an error (#8562)

---
 vlib/v/checker/checker.v                      |  6 +-
 .../checker/tests/eq_ne_op_wrong_type_err.out | 83 +++++++++++++++++++
 .../checker/tests/eq_ne_op_wrong_type_err.vv  | 25 ++++++
 3 files changed, 111 insertions(+), 3 deletions(-)
 create mode 100644 vlib/v/checker/tests/eq_ne_op_wrong_type_err.out
 create mode 100644 vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index f471a86869..38ed4e446f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -777,9 +777,9 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 	match infix_expr.op {
 		// .eq, .ne, .gt, .lt, .ge, .le, .and, .logical_or, .dot, .key_as, .right_shift {}
 		.eq, .ne {
-			is_alias_eq_struct := left.kind == .alias && right.kind == .struct_
-			is_struct_eq_alias := left.kind == .struct_ && right.kind == .alias
-			if is_alias_eq_struct || is_struct_eq_alias {
+			is_mismatch := (left.kind == .alias && right.kind in [.struct_, .array])
+				|| (right.kind == .alias && left.kind in [.struct_, .array])
+			if is_mismatch {
 				c.error('possible type mismatch of compared values of `$infix_expr.op` operation',
 					infix_expr.pos)
 			}
diff --git a/vlib/v/checker/tests/eq_ne_op_wrong_type_err.out b/vlib/v/checker/tests/eq_ne_op_wrong_type_err.out
new file mode 100644
index 0000000000..08a0cefd34
--- /dev/null
+++ b/vlib/v/checker/tests/eq_ne_op_wrong_type_err.out
@@ -0,0 +1,83 @@
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:10:16: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+    8 | 
+    9 | fn main() {
+   10 |     println(Aaa{} == 10)
+      |                   ~~
+   11 |     println(10 == Aaa{})
+   12 |     println(Aaa{} != 10)
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:11:13: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+    9 | fn main() {
+   10 |     println(Aaa{} == 10)
+   11 |     println(10 == Aaa{})
+      |                ~~
+   12 |     println(Aaa{} != 10)
+   13 |     println(10 != Aaa{})
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:12:16: error: infix expr: cannot use `int literal` (right expression) as `Aaa`
+   10 |     println(Aaa{} == 10)
+   11 |     println(10 == Aaa{})
+   12 |     println(Aaa{} != 10)
+      |                   ~~
+   13 |     println(10 != Aaa{})
+   14 |
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:13:13: error: infix expr: cannot use `Aaa` (right expression) as `int literal`
+   11 |     println(10 == Aaa{})
+   12 |     println(Aaa{} != 10)
+   13 |     println(10 != Aaa{})
+      |                ~~
+   14 | 
+   15 |     println(Aaa{0} == AAaa{0})
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:15:17: error: possible type mismatch of compared values of `==` operation
+   13 |     println(10 != Aaa{})
+   14 | 
+   15 |     println(Aaa{0} == AAaa{0})
+      |                    ~~
+   16 |     println(AAaa{0} == Aaa{0})
+   17 |     println(AAaa{1} != Aaa{1})
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:16:18: error: possible type mismatch of compared values of `==` operation
+   14 | 
+   15 |     println(Aaa{0} == AAaa{0})
+   16 |     println(AAaa{0} == Aaa{0})
+      |                     ~~
+   17 |     println(AAaa{1} != Aaa{1})
+   18 |     println(Aaa{1} != AAaa{1})
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:17:18: error: possible type mismatch of compared values of `!=` operation
+   15 |     println(Aaa{0} == AAaa{0})
+   16 |     println(AAaa{0} == Aaa{0})
+   17 |     println(AAaa{1} != Aaa{1})
+      |                     ~~
+   18 |     println(Aaa{1} != AAaa{1})
+   19 |
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:18:17: error: possible type mismatch of compared values of `!=` operation
+   16 |     println(AAaa{0} == Aaa{0})
+   17 |     println(AAaa{1} != Aaa{1})
+   18 |     println(Aaa{1} != AAaa{1})
+      |                    ~~
+   19 | 
+   20 |     arr := Arr([0])
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:21:14: error: possible type mismatch of compared values of `==` operation
+   19 | 
+   20 |     arr := Arr([0])
+   21 |     println(arr == [0])
+      |                 ~~
+   22 |     println([1] == arr)
+   23 |     println(arr != [0])
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:22:14: error: possible type mismatch of compared values of `==` operation
+   20 |     arr := Arr([0])
+   21 |     println(arr == [0])
+   22 |     println([1] == arr)
+      |                 ~~
+   23 |     println(arr != [0])
+   24 |     println([1] != arr)
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:23:14: error: possible type mismatch of compared values of `!=` operation
+   21 |     println(arr == [0])
+   22 |     println([1] == arr)
+   23 |     println(arr != [0])
+      |                 ~~
+   24 |     println([1] != arr)
+   25 | }
+vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv:24:14: error: possible type mismatch of compared values of `!=` operation
+   22 |     println([1] == arr)
+   23 |     println(arr != [0])
+   24 |     println([1] != arr)
+      |                 ~~
+   25 | }
diff --git a/vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv b/vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv
new file mode 100644
index 0000000000..a32f38df56
--- /dev/null
+++ b/vlib/v/checker/tests/eq_ne_op_wrong_type_err.vv
@@ -0,0 +1,25 @@
+struct Aaa {
+	i int
+}
+
+type AAaa = Aaa
+
+type Arr = []int
+
+fn main() {
+	println(Aaa{} == 10)
+	println(10 == Aaa{})
+	println(Aaa{} != 10)
+	println(10 != Aaa{})
+
+	println(Aaa{0} == AAaa{0})
+	println(AAaa{0} == Aaa{0})
+	println(AAaa{1} != Aaa{1})
+	println(Aaa{1} != AAaa{1})
+
+	arr := Arr([0])
+	println(arr == [0])
+	println([1] == arr)
+	println(arr != [0])
+	println([1] != arr)
+}