Add Style/ParenthesizedAssignments rule

src/ameba/rule/style/parenthesized_assignments.cr

@@ -0,0 +1,43 @@
+module Ameba::Rule::Style
+  # A rule that disallows assignments without parens in control expressions.
+  #
+  # For example, this is considered invalid:
+  #
+  # ```
+  # if foo = @foo
+  #   do_something
+  # end
+  # ```
+  #
+  # And should be replaced by the following:
+  #
+  # ```
+  # if (foo = @foo)
+  #   do_something
+  # end
+  # ```
+  #
+  # YAML configuration example:
+  #
+  # ```
+  # Style/ParenthesizedAssignments:
+  #   Enabled: true
+  # ```
+  class ParenthesizedAssignments < Base
+    properties do
+      enabled false
+      description "Disallows assignments without parens in control expressions"
+    end
+
+    MSG = "Missing parentheses around assignment"
+
+    def test(source, node : Crystal::If | Crystal::Unless | Crystal::Case | Crystal::While | Crystal::Until)
+      return unless (cond = node.cond).is_a?(Crystal::Assign)
+
+      issue_for cond, MSG do |corrector|
+        corrector.insert_before(cond, '(')
+        corrector.insert_after(cond, ')')
+      end
+    end
+  end
+end