Add Lint/UnusedPseudoMethodCall

spec/ameba/rule/lint/unused_pseudo_method_call_spec.cr

@@ -0,0 +1,181 @@
+require "../../../spec_helper"
+
+module Ameba::Rule::Lint
+  describe UnusedPseudoMethodCall do
+    subject = UnusedPseudoMethodCall.new
+
+    it "passes if typeof is unused" do
+      expect_no_issues subject, <<-CRYSTAL
+        typeof(1)
+        CRYSTAL
+    end
+
+    it "passes if as is unused" do
+      expect_no_issues subject, <<-CRYSTAL
+        as(Int32)
+        CRYSTAL
+    end
+
+    it "fails if pointerof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        pointerof(Int32)
+        # ^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if sizeof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        sizeof(Int32)
+        # ^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if instance_sizeof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        instance_sizeof(Int32)
+        # ^^^^^^^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if alignof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        alignof(Int32)
+        # ^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if instance_alignof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        instance_alignof(Int32)
+        # ^^^^^^^^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if offsetof is unused" do
+      expect_issue subject, <<-CRYSTAL
+        offsetof(Int32, 1)
+        # ^^^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if is_a? is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        foo.is_a?(Int32)
+        # ^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if as? is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        foo.as?(Int32)
+        # ^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if responds_to? is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        foo.responds_to?(:bar)
+        # ^^^^^^^^^^^^^^^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if nil? is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        foo.nil?
+        # ^^^^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if prefix not is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        !foo
+        # ^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "fails if suffix not is unused" do
+      expect_issue subject, <<-CRYSTAL
+        foo = 1
+        foo.!
+        # ^^^ error: Pseudo-method call is not used
+        CRYSTAL
+    end
+
+    it "passes if pointerof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = pointerof(Int32)
+        CRYSTAL
+    end
+
+    it "passes if sizeof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = sizeof(Int32)
+        CRYSTAL
+    end
+
+    it "passes if instance_sizeof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = instance_sizeof(Int32)
+        CRYSTAL
+    end
+
+    it "passes if alignof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = alignof(Int32)
+        CRYSTAL
+    end
+
+    it "passes if instance_alignof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = instance_alignof(Int32)
+        CRYSTAL
+    end
+
+    it "passes if offsetof is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = offsetof(Int32, 1)
+        CRYSTAL
+    end
+
+    it "passes if is_a? is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = is_a?(Int32)
+        CRYSTAL
+    end
+
+    it "passes if as? is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = as?(Int32)
+        CRYSTAL
+    end
+
+    it "passes if responds_to? is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = responds_to?(:foo)
+        CRYSTAL
+    end
+
+    it "passes if nil? is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = nil?
+        CRYSTAL
+    end
+
+    it "passes if prefix not is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = !true
+        CRYSTAL
+    end
+
+    it "passes if suffix not is used as an assign value" do
+      expect_no_issues subject, <<-CRYSTAL
+        var = true.!
+        CRYSTAL
+    end
+  end
+end

src/ameba/rule/lint/unused_pseudo_method_call.cr

@@ -0,0 +1,44 @@
+module Ameba::Rule::Lint
+  # A rule that disallows unused pseudo method calls (is_a?, sizeof, etc).
+  #
+  # For example, these are considered invalid:
+  #
+  # ```
+  # pointerof(foo)
+  # sizeof(Bar)
+  #
+  # def method
+  #   !!valid? if guard?
+  #   nil
+  # end
+  # ```
+  #
+  # YAML configuration example:
+  #
+  # ```
+  # Lint/UnusedPseudoMethodCall:
+  #   Enabled: true
+  # ```
+  class UnusedPseudoMethodCall < Base
+    properties do
+      since_version "1.7.0"
+      description "Disallows unused pseudo-method calls"
+    end
+
+    MSG = "Pseudo-method call is not used"
+
+    def test(source : Source)
+      AST::ImplicitReturnVisitor.new(self, source)
+    end
+
+    def test(
+      source,
+      node : Crystal::PointerOf | Crystal::SizeOf | Crystal::InstanceSizeOf |
+             Crystal::AlignOf | Crystal::InstanceAlignOf | Crystal::OffsetOf |
+             Crystal::IsA | Crystal::NilableCast | Crystal::RespondsTo | Crystal::Not,
+      in_macro : Bool,
+    )
+      issue_for node, MSG
+    end
+  end
+end