checker: fix negative cap, len checks in array init (#19694)

Author: shove70

vlib/v/checker/containers.v

@@ -338,6 +338,12 @@ fn (mut c Checker) check_array_init_para_type(para string, mut expr ast.Expr, po
 	if sym.kind !in [.int, .int_literal] {
 		c.error('array ${para} needs to be an int', pos)
 	}
+	if expr is ast.IntegerLiteral {
+		lit := expr as ast.IntegerLiteral
+		if lit.val.int() < 0 {
+			c.error('array ${para} can not be negative', lit.pos)
+		}
+	}
 }
 
 fn (mut c Checker) ensure_sumtype_array_has_default_value(node ast.ArrayInit) {

vlib/v/checker/tests/array_init_with_len_cap_err.out

@@ -0,0 +1,8 @@
+vlib/v/checker/tests/array_init_with_len_cap_err.vv:1:16: error: array len can not be negative
+    1 | _ = []int{len: -1}
+      |                ~~
+    2 | _ = []int{cap: -1}
+vlib/v/checker/tests/array_init_with_len_cap_err.vv:2:16: error: array cap can not be negative
+    1 | _ = []int{len: -1}
+    2 | _ = []int{cap: -1}
+      |                ~~

vlib/v/checker/tests/array_init_with_len_cap_err.vv

@@ -0,0 +1,2 @@
+_ = []int{len: -1}
+_ = []int{cap: -1}