foo.ts is resolved before foo.d.ts even if the latter is in files[]

Affects at least TS 2.7.2 and 2.6.2. This problem appears when compiling files separately, like we do under Bazel. Imagine this simple app `src/lib.ts` ``` export const a = 1; ``` `src/main.ts` ``` import {a} from './lib'; ``` Imagine `lib.ts` was compiled separately, so there already exists `dist/lib.d.ts` ``` export declare const a = 1; ``` Now, I want to compile `main.ts` as a separate program. Given `src/tsconfig.json` ``` { "compilerOptions": { "rootDirs": [ ".", "../dist" ], "outDir": "../dist", "declaration": true }, "files": [ "main.ts", // lib was compiled separately "../dist/lib.d.ts" ] } ``` We see that `lib.d.ts` is already in the program before resolution begins. However the compiler resolves the import statement to the `lib.ts` file instead, adding it to the program, and tries to emit on top of an input, so the error is ``` $ ./node_modules/.bin/tsc -p src error TS5055: Cannot write file '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/dist/lib.d.ts' because it would overwrite input file. ``` Okay, we didn't want `lib.ts` in the program, so we should just use `--noResolve` to prevent that, but it's also broken: ``` $ ./node_modules/.bin/tsc -p src --noResolve --traceResolution ======== Resolving module './lib' from '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/src/main.ts'. ======== Module resolution kind is not specified, using 'NodeJs'. 'rootDirs' option is set, using it to resolve relative module name './lib'. Checking if '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/src/' is the longest matching prefix for '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/src/lib' - 'true'. Checking if '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/dist/' is the longest matching prefix for '/usr/local/google/home/alexeagle/Projects/repro_ts_resolving_ts/src/lib' - 'false'. Longest matching prefix for '/usr/local/google/home/alexeag…