Improve pointless-reassignment to cover nested cases (#1727)

Previously this rule would only check expressions at the topmost
level of rule bodies. Now it checks expressions anywhere in the
policy.

Signed-off-by: Anders Eknert <anders@eknert.com>

Author: anderseknert

bundle/regal/rules/style/pointless-reassignment/pointless_reassignment.rego

@@ -17,16 +17,15 @@ report contains violation if {
 	violation := result.fail(rego.metadata.chain(), result.location(rule))
 }
 
-# pointless reassignment in rule body
+# pointless reassignment in expressions
 report contains violation if {
-	expr := input.rules[_].body[_]
+	some expr
+	ast.found.expressions[_][expr].terms[0].value[0].value == "assign"
 
 	not expr.with
-
-	[lhs, rhs] := ast.assignment_terms(expr.terms)
-
-	lhs.type == "var"
-	rhs.type == "var"
+	expr.terms[0].type == "ref"
+	expr.terms[1].type == "var"
+	expr.terms[2].type == "var"
 
 	violation := result.fail(rego.metadata.chain(), result.infix_expr_location(expr.terms))
 }

bundle/regal/rules/style/pointless-reassignment/pointless_reassignment_test.rego

@@ -67,6 +67,40 @@ test_fail_pointless_reassignment_in_rule_body if {
 	}}
 }
 
+test_fail_pointless_reassignment_in_rule_body_nested if {
+	module := ast.with_rego_v1(`
+	rule if {
+		foo := "foo"
+
+		comp := [bar |
+			bar := foo
+		]
+	}
+	`)
+	r := rule.report with input as module
+
+	r == {{
+		"category": "style",
+		"description": "Pointless reassignment of variable",
+		"level": "error",
+		"location": {
+			"col": 4,
+			"row": 10,
+			"end": {
+				"col": 10,
+				"row": 10,
+			},
+			"file": "policy.rego",
+			"text": "\t\t\tbar := foo",
+		},
+		"related_resources": [{
+			"description": "documentation",
+			"ref": config.docs.resolve_url("$baseUrl/$category/pointless-reassignment", "style"),
+		}],
+		"title": "pointless-reassignment",
+	}}
+}
+
 test_success_pointless_reassignment_in_rule_body_using_with if {
 	module := ast.with_rego_v1(`
 	foo := input