checker: forbid multiple pointer yields (#11105)

vlib/v/checker/checker.v

@@ -7117,6 +7117,13 @@ pub fn (mut c Checker) prefix_expr(mut node ast.PrefixExpr) ast.Type {
 	right_type := c.expr(node.right)
 	c.inside_ref_lit = old_inside_ref_lit
 	node.right_type = right_type
+	if node.op == .amp {
+		if mut node.right is ast.PrefixExpr {
+			if node.right.op == .amp {
+				c.error('unexpected `&`, expecting expression', node.right.pos)
+			}
+		}
+	}
 	// TODO: testing ref/deref strategy
 	if node.op == .amp && !right_type.is_ptr() {
 		mut expr := node.right

vlib/v/checker/tests/multiple_pointer_yield_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/multiple_pointer_yield_err.vv:9:8: error: unexpected `&`, expecting expression
+    7 | fn main() {
+    8 |     f := Fail{}
+    9 |     foo(&&&f)
+      |           ^
+   10 | }

vlib/v/checker/tests/multiple_pointer_yield_err.vv

@@ -0,0 +1,10 @@
+struct Fail {
+	name string
+}
+
+fn foo(bar &&&Fail) {}
+
+fn main() {
+	f := Fail{}
+	foo(&&&f)
+}