Add Lint/MissingBlockArgument rule

spec/ameba/rule/lint/missing_block_argument_spec.cr

@@ -0,0 +1,42 @@
+require "../../../spec_helper"
+
+module Ameba::Rule::Lint
+  subject = MissingBlockArgument.new
+
+  describe MissingBlockArgument do
+    it "passes if the block argument is defined" do
+      expect_no_issues subject, <<-CRYSTAL
+        def foo(&)
+          yield 42
+        end
+
+        def bar(&block)
+          yield 24
+        end
+
+        def baz(a, b, c, &block)
+          yield a, b, c
+        end
+        CRYSTAL
+    end
+
+    it "reports if the block argument is missing" do
+      expect_issue subject, <<-CRYSTAL
+        def foo
+          # ^^^ error: Missing anonymous block argument. Use `&` as an argument name to indicate yielding method.
+          yield 42
+        end
+
+        def bar
+          # ^^^ error: Missing anonymous block argument. Use `&` as an argument name to indicate yielding method.
+          yield 24
+        end
+
+        def baz(a, b, c)
+          # ^^^ error: Missing anonymous block argument. Use `&` as an argument name to indicate yielding method.
+          yield a, b, c
+        end
+        CRYSTAL
+    end
+  end
+end