Freeze string literals when not mutated.

I wrote a utility that helps find areas where you could optimize your program using a frozen string instead of a string literal, it's called [let_it_go](https://github.com/schneems/let_it_go). After going through the output and adding `.freeze` I was able to eliminate the creation of 1,114 string objects on EVERY request to [codetriage](codetriage.com). How does this impact execution?

To look at memory:

```ruby
require 'get_process_mem'

mem = GetProcessMem.new
GC.start
GC.disable
1_114.times { " " }
before = mem.mb

after = mem.mb
GC.enable
puts "Diff: #{after - before} mb"

```

Creating 1,114 string objects results in `Diff: 0.03125 mb` of RAM allocated on every request. Or 1mb every 32 requests.

To look at raw speed:

```ruby
require 'benchmark/ips'

number_of_objects_reduced = 1_114

Benchmark.ips do |x|
  x.report("freeze")    { number_of_objects_reduced.times { " ".freeze } }
  x.report("no-freeze") { number_of_objects_reduced.times { " " } }
end
```

We get the results

```
Calculating -------------------------------------
              freeze     1.428k i/100ms
           no-freeze   609.000  i/100ms
-------------------------------------------------
              freeze     14.363k (± 8.5%) i/s -     71.400k
           no-freeze      6.084k (± 8.1%) i/s -     30.450k
```

Now we can do some maths:

```ruby
ips = 6_226k # iterations / 1 second
call_time_before = 1.0 / ips # seconds per iteration 

ips = 15_254 # iterations / 1 second
call_time_after = 1.0 / ips # seconds per iteration 

diff = call_time_before - call_time_after

number_of_objects_reduced * diff * 100

# => 0.4530373333993266 miliseconds saved per request
```

So we're shaving off 1 second of execution time for every 220 requests. 

Is this going to be an insane speed boost to any Rails app: nope. Should we merge it: yep. 

p.s. If you know of a method call that doesn't modify a string input such as [String#gsub](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37) please [give me a pull request to the appropriate file](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37), or open an issue in LetItGo so we can track and freeze more strings. 

Keep those strings Frozen

![](https://www.dropbox.com/s/z4dj9fdsv213r4v/let-it-go.gif?dl=1)

Fix exception overwritten for parameters fetch method

Since the counter cache was properly being updated, the model became
stale. Simply reloading the model before attempting to destroy is
sufficient for this case. I believe this is enough of an edge case to be
a valid change to the tests, even though it represents a potential
breaking change.

Also removes a false positive test that depends on the fixed bug:

At this time, counter_cache does not work with polymorphic relationships
(which is a bug). The test was added to make sure that no
StaleObjectError is raised when the car is destroyed. No such error is
currently raised because the lock version is not incremented by
appending a wheel to the car.

Furthermore, `assert_difference` succeeds because `car.wheels.count`
does not check the counter cache, but the collection size. The test will
fail if it is replaced with `car.wheels_count || 0`.

Fix `TimeWithZone#eql?` to handle `TimeWithZone` created from `DateTime`

Before:

```ruby
  twz = DateTime.now.in_time_zone
  twz.eql?(twz.dup) => false
```

Now:

```ruby
  twz = DateTime.now.in_time_zone
  twz.eql?(twz.dup) => true
```

Please notice that this fix the `TimeWithZone` comparison to itself,
not to `DateTime`. Based on #3725, `DateTime` should not be equal to
`TimeWithZone`.

Fix formatting of force_ssl options documentation [ci skip]

[ci skip] Fix typo in #any? RDoc

Added examples to DateAndTime::Calculations [ci skip]

When executing an `ActionController::Parameters#fetch` with a block
that raises a `KeyError` the raised `KeyError` will be rescued and
converted to an `ActionController::ParameterMissing` exception,
covering up the original exception.

[Jonas Schubert Erlandsson & Roque Pinel]

Ensure that 'ActionController::Parameters' can still be passed to AR …

This code is so fucked. Things that cause this bug not to replicate:

- Defining the validation before the association (we end up calling
  `uniq!` on the errors in the autosave validation)
- Adding `accepts_nested_attributes_for` (I have no clue why. The only
  thing it does that should affect this is adds `autosave: true` to the
  inverse reflection, and doing that manually doesn't fix this).

This solution is a hack, and I'm almost certain there's a better way to
go about it, but this shouldn't cause a huge hit on validation times,
and is the simplest way to get it done.

Fixes #20874.

Add a note about default_scope and create records [ci skip]

Since nested hashes are also instances of
`ActionController::Parameters`, and we're explicitly looking to work
with a hash for nested attributes, this caused breakage in several
points.

This is the minimum viable fix for the issue (and one that I'm not
terribly fond of). I can't think of a better place to handle this at the
moment. I'd prefer to use some sort of solution that doesn't special
case AC::Parameters, but we can't use something like `to_h` or `to_a`
since `Enumerable` adds both.

While I've added a trivial test case for verifying this fix in
isolation, we really need better integration coverage to prevent
regressions like this in the future. We don't actually have a lot of
great places for integration coverage at the moment, so I'm deferring it
for now.

Fixes #20922.

 Replaced render :text with render :plain in AC gem bug report template

 - Followup of https://github.com/rails/rails/pull/20929.
 [ci skip]

use `plain` option instead of deprecated `text` option

this will silence deprecation warnings

Stop using deprecated `render :text` in test

This will silence deprecation warnings.

Most of the test can be changed from `render :text` to render `:plain`
or `render :body` right away. However, there are some tests that needed
to be fixed by hand as they actually assert the default Content-Type
returned from `render :body`.

Add deprecation warning for `render :text`

We've started on discouraging the usage of `render :text` in #12374.
This is a follow-up commit to make sure that we print out the
deprecation warning.

this way we don't need to call `to_unsafe_h` to get access to ask
questions about the underlying hash

Silence deprecation warning from force reload

now `hash_filter` doesn't need to know about the `Parameters` class

Since we proved that `element` is always of type `Parameter`, we know
that it will always respond to `permit`, so lets remove this conditional

Manually merged to fix conflicts.

ActiveSupport::HashWithIndifferentAccess select and reject should return enumerator if called without block

`element` can never be a hash because:

1. `slice` returns a Parameters object and calls each on it: https://github.com/rails/rails/blob/cb3f25593b1137e344086364d4b1a52c08e8eb3b/actionpack/lib/action_controller/metal/strong_parameters.rb#L656
2. `each` which is implemented by `each_pair` will call `convert_hashes_to_parameters` on the value: https://github.com/rails/rails/blob/cb3f25593b1137e344086364d4b1a52c08e8eb3b/actionpack/lib/action_controller/metal/strong_parameters.rb#L192-197
3. `convert_hashes_to_parameters` will convert any hash objects in to parameters objects: https://github.com/rails/rails/blob/cb3f25593b1137e344086364d4b1a52c08e8eb3b/actionpack/lib/action_controller/metal/strong_parameters.rb#L550-566

Now that the value is cached on the stack,
`array_of_permitted_scalars_filter` is exactly the same as
`array_of_permitted_scalars?`, so lets just have one

this way the method doesn't have to know what the new params object is,
it just yields to a block.  This change also caches the value of
`self[key]` on the stack

We should disconnect `array_of_permitted_scalars_filter` from the
instance so that we can make hash filtering functional.  For now, pull
the conditional up out of that method