Resolving module declaration path should prefer d.ts over .ts

[saschanaz]

TypeScript Version: master branch

Repro:

1. Get this file and unzip: ts-module-declaration-resolving.zip
2. Run tsc on the test subdirectory

Expected behavior:

test-output directory should only contain inner.js

Actual behavior:

test-output directory contains outer.js and test/inner.js

Why?:

import test from "../outer.js" causes this bug, it should try finding outer.d.ts before outer.ts to remove the need to recompile.

[mhegazy]

.ts files are considered sources, where .d.ts are considered outputs. the compiler will always prefer a source file for an output when it is resolving modules, the rational, is that sources are more up-to-date than an output.

In general, do not put .d.ts next to your .ts if you intend to import them, use --outDir or --declrationDir instead.