From 93e270f87aa0e1df210d9c96c15a49c9cd8a0ec6 Mon Sep 17 00:00:00 2001
From: Michael Miller <icy.arctic.fox@gmail.com>
Date: Sat, 17 Apr 2021 09:38:29 -0600
Subject: [PATCH] Support variables and methods for type matcher (be_a).

Addresses https://github.com/icy-arctic-fox/spectator/issues/25
---
 spec/matchers/type_matcher_spec.cr     | 26 ++++++++++++++++++++++++++
 src/spectator/dsl/matchers.cr          |  2 +-
 src/spectator/matchers/type_matcher.cr |  5 +++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 spec/matchers/type_matcher_spec.cr

diff --git a/spec/matchers/type_matcher_spec.cr b/spec/matchers/type_matcher_spec.cr
new file mode 100644
index 0000000..22d218e
--- /dev/null
+++ b/spec/matchers/type_matcher_spec.cr
@@ -0,0 +1,26 @@
+require "../spec_helper"
+
+Spectator.describe Spectator::Matchers::TypeMatcher do
+  context String do # Sets `described_class` to String
+    def other_type
+      Int32
+    end
+
+    describe "#|" do
+      it "works on sets" do
+        super_set = (described_class | other_type)
+
+        expect(42).to be_kind_of(super_set)
+        expect("foo").to be_a(super_set)
+      end
+    end
+
+    it "works on described_class" do
+      expect("foo").to be_a_kind_of(described_class)
+    end
+
+    it "works on plain types" do
+      expect(42).to be_a(Int32)
+    end
+  end
+end
diff --git a/src/spectator/dsl/matchers.cr b/src/spectator/dsl/matchers.cr
index 9deb404..8332c44 100644
--- a/src/spectator/dsl/matchers.cr
+++ b/src/spectator/dsl/matchers.cr
@@ -77,7 +77,7 @@ module Spectator
     # expect(x).to be_a(Int32 | String)
     # ```
     macro be_a(expected)
-      ::Spectator::Matchers::TypeMatcher({{expected}}).new
+      ::Spectator::Matchers::TypeMatcher.create({{expected}})
     end
 
     # Indicates that some value should be of a specified type.
diff --git a/src/spectator/matchers/type_matcher.cr b/src/spectator/matchers/type_matcher.cr
index f8401d4..325265a 100644
--- a/src/spectator/matchers/type_matcher.cr
+++ b/src/spectator/matchers/type_matcher.cr
@@ -4,6 +4,11 @@ module Spectator::Matchers
   # Matcher that tests a value is of a specified type.
   # The values are compared with the `Object#is_a?` method.
   struct TypeMatcher(Expected) < StandardMatcher
+    # Alternate constructor that works with constant types and types from variables.
+    def self.create(type : T.class) forall T
+      TypeMatcher(T).new
+    end
+
     # Short text about the matcher's purpose.
     # This explains what condition satisfies the matcher.
     # The description is used when the one-liner syntax is used.