class SimpleCov::Result::SourceFileBuilder

silent drop (see #980).
is no longer present on disk so the caller can warn about the
hash, sorts them by filename, and surfaces filenames whose source
Constructs ‘SimpleCov::SourceFile` instances from a raw coverage

def build_source_file(filename, coverage) 

def build_source_file(filename, coverage)
  unless File.file?(filename)
    @missing_source_files << filename
    return
  end
  SimpleCov::SourceFile.new(
    filename,
    stringify_outer_keys(coverage),
    loaded: !@not_loaded_files.include?(filename)
  )
end

def call 

def call
  SimpleCov::FileList.new(
    @original_result
      .filter_map { |filename, coverage| build_source_file(filename, coverage) }
      .sort_by(&:filename)
  )
end

def initialize(original_result, not_loaded_files:) 

def initialize(original_result, not_loaded_files:)
  @original_result = original_result
  @not_loaded_files = not_loaded_files
  @missing_source_files = []
end

def stringify_outer_keys(coverage)

so only the outer hash needs normalizing.
stringified-Array branch/method keys via `restore_ruby_data_structure`,
SourceFile reads with strings, and handles both Array and
`:methods`); resultsets loaded from disk are already string-keyed.
`Coverage.result` returns symbol keys (`:lines`, `:branches`, 
def stringify_outer_keys(coverage)
  coverage.transform_keys(&:to_s)
end