Added local variable methods to Binding

This adds the following methods:

* Binding#local_variable_set
* Binding#local_variable_get
* Binding#local_variable_defined?

Fixes #2992
Closes #3372

core/binding.rb

@@ -58,4 +58,59 @@ def eval(expr, filename=nil, lineno=nil)
   def local_variables
     variables.local_variables
   end
+
+  def local_variable_set(name, value)
+    unless name.is_a?(Symbol)
+      name = Rubinius::Type.coerce_to(name, String, :to_str).to_sym
+    end
+
+    vars = variables
+
+    # If a local variable is defined in a parent scope we should update the
+    # variable in said scope and all child scopes, instead of _only_ setting it
+    # in the current scope.
+    while vars
+      meth = vars.method
+
+      if meth.local_names.include?(name)
+        return vars.set_local(meth.local_slot(name), value)
+      elsif vars.eval_local_defined?(name)
+        return vars.set_eval_local(name, value)
+      end
+
+      vars = vars.parent
+    end
+
+    variables.set_eval_local(name, value)
+  end
+
+  def local_variable_get(name)
+    unless name.is_a?(Symbol)
+      name = Rubinius::Type.coerce_to(name, String, :to_str).to_sym
+    end
+
+    vars = variables
+
+    while vars
+      meth = vars.method
+
+      if meth.local_names.include?(name)
+        return vars.locals[meth.local_slot(name)]
+      elsif vars.eval_local_defined?(name)
+        return vars.get_eval_local(name)
+      end
+
+      vars = vars.parent
+    end
+
+    raise NameErrror, "local variable #{name.inspect} not defined for #{inspect}"
+  end
+
+  def local_variable_defined?(name)
+    unless name.is_a?(Symbol)
+      name = Rubinius::Type.coerce_to(name, String, :to_str).to_sym
+    end
+
+    variables.local_defined?(name)
+  end
 end

core/variable_scope.rb

@@ -136,6 +136,8 @@ def local_defined?(name)
         return true if vars.eval_local_defined?(name, false)
         vars = vars.parent
       end
+
+      false
     end
 
     def local_layout

spec/ruby/core/binding/local_variable_defined_p_spec.rb

@@ -0,0 +1,50 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe 'Binding#local_variable_defined?' do
+  it 'returns false when a variable is not defined' do
+    binding.local_variable_defined?(:foo).should == false
+  end
+
+  it 'returns true when a regular local variable is defined' do
+    foo = 10
+
+    binding.local_variable_defined?(:foo).should == true
+  end
+
+  it 'returns true when a local variable is defined using eval()' do
+    bind = binding
+
+    bind.eval('foo = 10')
+
+    bind.local_variable_defined?(:foo).should == true
+  end
+
+  it 'returns true when a local variable is defined using Binding#local_variable_set' do
+    bind = binding
+
+    bind.local_variable_set(:foo, 10)
+
+    bind.local_variable_defined?(:foo).should == true
+  end
+
+  it 'returns true when a local variable is defined in a parent scope' do
+    foo = 10
+
+    proc { binding.local_variable_defined?(:foo) }.call.should == true
+  end
+
+  it 'allows usage of a String as the variable name' do
+    foo = 10
+
+    binding.local_variable_defined?('foo').should == true
+  end
+
+  it 'allows usage of an object responding to #to_str as the variable name' do
+    foo  = 10
+    name = mock(:obj)
+
+    name.stub!(:to_str).and_return('foo')
+
+    binding.local_variable_defined?(name).should == true
+  end
+end

spec/ruby/core/binding/local_variable_get_spec.rb

@@ -0,0 +1,34 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe 'Binding#local_variable_get' do
+  it 'gets a local variable defined before the Binding' do
+    number = 10
+
+    binding.local_variable_get(:number).should == 10
+  end
+
+  it 'gets a local variable defined in the Binding' do
+    bind = binding
+
+    bind.local_variable_set(:number, 10)
+    bind.local_variable_get(:number).should == 10
+  end
+
+  it 'gets a local variable defined using eval()' do
+    bind = binding
+
+    bind.eval('number = 10')
+
+    bind.local_variable_get(:number).should == 10
+  end
+
+  it 'gets a local variable defined in a parent scope' do
+    number = 10
+
+    proc { binding.local_variable_get(:number) }.call.should == 10
+  end
+
+  it 'raises NameError for an undefined local variable' do
+    proc { binding.local_variable_get(:cats) }.should raise_error(NameError)
+  end
+end

spec/ruby/core/binding/local_variable_set_spec.rb

@@ -0,0 +1,54 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe 'Binding#local_variable_set' do
+  it 'sets a new local variable' do
+    bind = binding
+
+    bind.local_variable_set(:number, 10)
+    bind.local_variable_get(:number).should == 10
+  end
+
+  it 'sets a local variable using a String as the variable name' do
+    bind = binding
+
+    bind.local_variable_set('number', 10)
+    bind.local_variable_get('number').should == 10
+  end
+
+  it 'sets a local variable using an object responding to #to_str as the variable name' do
+    bind = binding
+    name = mock(:obj)
+
+    name.stub!(:to_str).and_return('number')
+
+    bind.local_variable_set(name, 10)
+    bind.local_variable_get(name).should == 10
+  end
+
+  it 'scopes new local variables to the receiving Binding' do
+    bind = binding
+
+    bind.local_variable_set(:number, 10)
+
+    proc { number }.should raise_error(NameError)
+  end
+
+  it 'overwrites an existing local variable defined before a Binding' do
+    number = 10
+    bind   = binding
+
+    bind.local_variable_set(:number, 20)
+
+    number.should == 20
+  end
+
+  it 'overwrites a local variable defined using eval()' do
+    bind = binding
+
+    bind.eval('number = 10')
+
+    bind.local_variable_set(:number, 20)
+
+    bind.local_variable_get(:number).should == 20
+  end
+end