Fix a copypasto bug. Also rename the parameter in question to not shadow the 'file' builtin, and fix up a docstring a little.
Fix a copypasto bug. Also rename the parameter in question to not shadow the
'file' builtin, and fix up a docstring a little.

Hat tip to Sebastian Kreft Carreno at Google for noticing the bug.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@169887 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang