From e2334d8b62ab49b338e1f1f58973fbd3e575eebf Mon Sep 17 00:00:00 2001
From: shove <shove@163.com>
Date: Fri, 5 Jan 2024 18:22:08 +0800
Subject: [PATCH] parser: fix checking for invalid PrefixExpr (fix #20388)
 (#20392)

---
 vlib/v/parser/expr.v                 | 10 ++++++++++
 vlib/v/parser/tests/prefix_err_1.out |  3 +++
 vlib/v/parser/tests/prefix_err_1.vv  |  1 +
 vlib/v/parser/tests/prefix_err_2.out |  3 +++
 vlib/v/parser/tests/prefix_err_2.vv  |  1 +
 5 files changed, 18 insertions(+)
 create mode 100644 vlib/v/parser/tests/prefix_err_1.out
 create mode 100644 vlib/v/parser/tests/prefix_err_1.vv
 create mode 100644 vlib/v/parser/tests/prefix_err_2.out
 create mode 100644 vlib/v/parser/tests/prefix_err_2.vv

diff --git a/vlib/v/parser/expr.v b/vlib/v/parser/expr.v
index 08503b01c7..d82130d227 100644
--- a/vlib/v/parser/expr.v
+++ b/vlib/v/parser/expr.v
@@ -666,7 +666,17 @@ fn (mut p Parser) infix_expr(left ast.Expr) ast.Expr {
 		p.inside_in_array = true
 	}
 
+	right_op_pos := p.tok.pos()
 	right = p.expr(precedence)
+	if op in [.plus, .minus, .mul, .div, .mod, .lt, .eq] && mut right is ast.PrefixExpr {
+		mut right_expr := right.right
+		for mut right_expr is ast.ParExpr {
+			right_expr = right_expr.expr
+		}
+		if right.op in [.plus, .minus, .mul, .div, .mod, .lt, .eq] && right_expr.is_pure_literal() {
+			p.error_with_pos('invalid expression: unexpected token `${op}`', right_op_pos)
+		}
+	}
 	if is_key_in {
 		p.inside_in_array = false
 	}
diff --git a/vlib/v/parser/tests/prefix_err_1.out b/vlib/v/parser/tests/prefix_err_1.out
new file mode 100644
index 0000000000..974bf684f1
--- /dev/null
+++ b/vlib/v/parser/tests/prefix_err_1.out
@@ -0,0 +1,3 @@
+vlib/v/parser/tests/prefix_err_1.vv:1:9: error: invalid expression: unexpected token `-`
+    1 | _ = 5 - - -5
+      |         ^
diff --git a/vlib/v/parser/tests/prefix_err_1.vv b/vlib/v/parser/tests/prefix_err_1.vv
new file mode 100644
index 0000000000..04f48354be
--- /dev/null
+++ b/vlib/v/parser/tests/prefix_err_1.vv
@@ -0,0 +1 @@
+_ = 5 - - -5
diff --git a/vlib/v/parser/tests/prefix_err_2.out b/vlib/v/parser/tests/prefix_err_2.out
new file mode 100644
index 0000000000..65d09ba0d7
--- /dev/null
+++ b/vlib/v/parser/tests/prefix_err_2.out
@@ -0,0 +1,3 @@
+vlib/v/parser/tests/prefix_err_2.vv:1:9: error: invalid expression: unexpected token `-`
+    1 | _ = 5 - - (((-5)))
+      |         ^
diff --git a/vlib/v/parser/tests/prefix_err_2.vv b/vlib/v/parser/tests/prefix_err_2.vv
new file mode 100644
index 0000000000..74edf5d7e0
--- /dev/null
+++ b/vlib/v/parser/tests/prefix_err_2.vv
@@ -0,0 +1 @@
+_ = 5 - - (((-5)))