TypeScript Version: 2.7.0-dev.20171112

On case-insensitive systems, projects with forceConsistentCasingInFileNames enabled through an extended config seem to cause include conflicts when a path contains upper-case letters.

Seems to be the exact same (closed) issue as #16875

Code

tsc                             # works
tsc -p tsconfig.json            # works
tsc -p tsconfig.extended.json   # error

where tsconfig.extended.json is only the following:

{
  "extends": "./tsconfig.json"
}

with "forceConsistentCasingInFileNames": true is set in tsconfig.json

Expected behavior:
No errors to be produced.

Actual behavior:

error TS1149: File name '/Users/username/path/to/app/src/index.ts' differs from already included file name '/users/username/path/to/app/src/index.ts' only in casing.
error TS1149: File name '/Users/username/path/to/app/node_modules/@types/some-lib/index.d.ts' differs from already included file name '/users/username/path/to/app/node_modules/@types/some-lib/index.d.ts' only in casing.

Note: The original case /Users/... conflicting with a forced downcase /users/...