Fix issue setting content_for value with method param

sinatra-contrib/lib/sinatra/capture.rb

@@ -97,8 +97,7 @@ module Sinatra
         result = block[*args]
       elsif current_engine == :erb || current_engine == :slim
         @_out_buf, _buf_was = '', @_out_buf
-        block[*args]
-        result = eval('@_out_buf', block.binding)
+        result = block.call(*args)
         @_out_buf = _buf_was
       else
         buffer     = eval '_buf if defined?(_buf)', block.binding

sinatra-contrib/spec/content_for/parameter_value.erb

@@ -0,0 +1 @@
+<% content_for :foo, 'foo' %>

sinatra-contrib/spec/content_for/parameter_value.erubis

@@ -0,0 +1 @@
+<% content_for :foo, 'foo' %>

sinatra-contrib/spec/content_for/parameter_value.haml

@@ -0,0 +1 @@
+- content_for :foo, 'foo'

sinatra-contrib/spec/content_for/parameter_value.slim

@@ -0,0 +1 @@
+- content_for :foo, 'foo'

sinatra-contrib/spec/content_for_spec.rb

@@ -210,6 +210,11 @@ describe Sinatra::ContentFor do
             expect(body).to eq("bar")
           end
 
+          it 'renders content set as parameter' do
+            expect(get('/parameter_value')).to be_ok
+            expect(body).to eq("foo")
+          end
+
           it 'renders blocks declared with the same key you use when rendering' do
             expect(get('/same_key')).to be_ok
             expect(body).to eq("foo")