Add spec for missing or faulty to_proc methods

Followup: ruby#14463

Author: byroot

spec/ruby/language/fixtures/send.rb

@@ -81,6 +81,16 @@ def to_proc
     end
   end
 
+  class RawToProc
+    def initialize(to_proc)
+      @to_proc = to_proc
+    end
+
+    def to_proc
+      @to_proc
+    end
+  end
+
   class ToAry
     def initialize(obj)
       @obj = obj

spec/ruby/language/send_spec.rb

@@ -106,6 +106,24 @@
     specs.yield_now(&o).should == :from_to_proc
   end
 
+  ruby_version_is "3.5" do
+    it "raises TypeError if 'to_proc' doesn't return a Proc" do
+      o = LangSendSpecs::RawToProc.new(42)
+
+      -> {
+        specs.makeproc(&o)
+      }.should raise_error(TypeError, "can't convert LangSendSpecs::RawToProc to Proc (LangSendSpecs::RawToProc#to_proc gives Integer)")
+    end
+
+    it "raises TypeError if block object isn't a Proc and doesn't respond to `to_proc`" do
+      o = Object.new
+
+      -> {
+        specs.makeproc(&o)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Proc")
+    end
+  end
+
   it "raises a SyntaxError with both a literal block and an object as block" do
     -> {
       eval "specs.oneb(10, &l){ 42 }"