Closes Homebrew/homebrew#19324.

It was pointed out that this isn't used at all.

Closes Homebrew/homebrew#19074.

After converting to Pathname to create paths, using '+=' will result in
path concatenation by '/', which result in weird path like
'gcc--svn/-HEAD'. This patch should fix this.

Closes Homebrew/homebrew#19233.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Currently we check if "tag" is present in LANGUAGE_MODULES for every
String dep, even if tag is nil. Stop doing this, and make the
LANGUAGE_MODULES array into a Set instead to improve lookup performance.

Closes Homebrew/homebrew#19227.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

See 05a456c231dc6da7cb0f7c70cb21feaf9a0d803c; same story.

This is an internal method, but is called a bunch of times in
performance-critical codepaths, and is ultra slow because the constant
is interpoplated into the Regexp each time the method is called.

Alas, this has been fixed in Ruby 1.9+.

A FormulaPin object is created every time Formula is instantiated, so
don't do filesystem operations or Pathname concatenation eagerly.

This method (well, really, #join) is *twice* as slow as simple
concatenation, and shouldn't really be used at all in non-Formula code.

Benchmark.bm do |b|
  b.report("before") do
    100_000.times { /(\.#{MacOS.cat}\.bottle\.(\d+\.)?tar\.gz)$/ }
  end
  b.report("after ") do
    100_000.times { /(\.#{MacOS.cat}\.bottle\.(\d+\.)?tar\.gz)$/o }
  end
end
            user     system      total        real
before 35.400000   0.140000  35.540000 ( 35.619674)
after   0.020000   0.000000   0.020000 (  0.016662)

Closes Homebrew/homebrew#19192.

Closes Homebrew/homebrew#18835.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

This behavior is now tested at more appropriate levels in
test_software_spec, test_formula_spec_selection, and
test_formula_validation.

These tests document the relative precedence of the stable, bottle,
devel, and head specifications, and the conditions that can influence
which is selected (e.g. command-line flags).

It seems only natural that this should be possible, or at the very
least, it should not result in calling methods on nil.

The initializer for Formula does a number of validations, but it does
them in a weird order, and some attributes aren't validated under
certain circumstances. This became even more of a mess when most
software package attributes were moved into the SoftwareSpec class.

This commit removes the last vestiges of storing these attributes as
instance variables. In particular, it eliminates #set_instance_variable
and #validate_variable, replacing them with methods that operate on
SoftwareSpec instances, and generate more useful errors.

Doing these validations unconditionally in the initializer means we bail
out much earlier if the formula has invalid attributes or is not fully
specified, and no longer need to validate in #prefix.

Technically we don't need to validate in #brew either, but we continue
to do so anyway as a safety measure, and because we cannot enforce calls
to super in subclasses.

And by extension, `cleanup`.

Fixes Homebrew/homebrew#18658.

Closes Homebrew/homebrew#19083.

It was pointed out that 'raring' is a rare word can be confusing to
non-native speakers.

Closes Homebrew/homebrew#18659, see that for details.

Also include a writability check for lib.

Closes Homebrew/homebrew#18571.