From d45ef5990b9eba9770745a509ede1da4f392f710 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 7 Jun 2017 16:11:06 +0200
Subject: [PATCH 1/2] Add TypeNode#has_method?

---
 src/compiler/crystal/macros.cr         | 6 ++++++
 src/compiler/crystal/macros/methods.cr | 9 +++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/compiler/crystal/macros.cr b/src/compiler/crystal/macros.cr
index 52668f91c810..90f69ef59b7d 100644
--- a/src/compiler/crystal/macros.cr
+++ b/src/compiler/crystal/macros.cr
@@ -1543,6 +1543,12 @@ module Crystal::Macros
     def methods : ArrayLiteral(Def)
     end
 
+    # Returns `true` if this type has a method. For example `default_options`
+    # (the name you pass to this method is "default_options" or :default_options
+    # in this cases).
+    def has_method?(name : StringLiteral | SymbolLiteral) : BoolLiteral
+    end
+
     # Returns true if this type has an attribute. For example `@[Flags]`
     # or `@[Packed]` (the name you pass to this method is "Flags" or "Packed"
     # in these cases).
diff --git a/src/compiler/crystal/macros/methods.cr b/src/compiler/crystal/macros/methods.cr
index ce5543df332c..259b92d2e3ad 100644
--- a/src/compiler/crystal/macros/methods.cr
+++ b/src/compiler/crystal/macros/methods.cr
@@ -1346,6 +1346,11 @@ module Crystal
         end
       when "methods"
         interpret_argless_method(method, args) { TypeNode.methods(type) }
+      when "has_method?"
+        interpret_one_arg_method(method, args) do |arg|
+          value = arg.to_string("argument to 'TypeNode#has_method?'")
+          TypeNode.has_method?(type, value)
+        end
       when "has_attribute?"
         interpret_one_arg_method(method, args) do |arg|
           value = arg.to_string("argument to 'TypeNode#has_attribute?'")
@@ -1533,6 +1538,10 @@ module Crystal
       ArrayLiteral.new(defs)
     end
 
+    def self.has_method?(type, name)
+      BoolLiteral.new(!!type.has_def?(name))
+    end
+
     def self.overrides?(type, target, method)
       overrides = type.lookup_defs(method).any? do |a_def|
         a_def.owner != target && a_def.macro_owner != target && !target.implements?(a_def.owner)

From fe3ae02183f769a1dbfc846f3d684d861116f226 Mon Sep 17 00:00:00 2001
From: Sijawusz Pur Rahnama <sija@sija.pl>
Date: Wed, 7 Jun 2017 16:37:41 +0200
Subject: [PATCH 2/2] Add specs for TypeNode#has_method?

---
 spec/compiler/codegen/macro_spec.cr | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/spec/compiler/codegen/macro_spec.cr b/spec/compiler/codegen/macro_spec.cr
index ad02ea2785f8..b5bbbc1bd8f1 100644
--- a/spec/compiler/codegen/macro_spec.cr
+++ b/spec/compiler/codegen/macro_spec.cr
@@ -1601,6 +1601,30 @@ describe "Code gen: macro" do
       )).to_b.should be_false
   end
 
+  it "determines if method exists (true)" do
+    run(%(
+      class Foo
+        def foo
+          42
+        end
+      end
+
+      {{ Foo.has_method?(:foo) }}
+      )).to_b.should be_true
+  end
+
+  it "determines if method exists (false)" do
+    run(%(
+      class Foo
+        def foo
+          42
+        end
+      end
+
+      {{ Foo.has_method?(:bar) }}
+      )).to_b.should be_false
+  end
+
   it "forwards file location" do
     run(%(
       macro foo