npm link forces two imports of the same type to be compared structurally

[hiroshi-cl]

TypeScript Version: 2.1.4, 2.1.6, 2.2.1

(my environment: node 7.7.3, OS X El Capitan)

Code

See > https://github.com/hiroshi-cl/bug-sample-tsc-crash

Expected behavior:

Some compiled code / user-friendly error message

Actual behavior:

crash (memory leak?)

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory

[sandersn]

Still repros on master.

[sandersn]

This appears to be two bugs.

1. npm link forces the type Either from import { Either } from 'monet' to be different in def/src/index.ts vs use/src/index.ts. Normally the compiler is able to recognise that these are the same type and only create one type object. With a linked package, however, it doesn't know the types are identical so it creates two and is forced to compare them structurally.
2. monet is a monad library and the compiler can't compare these types structurally in a reasonable amount of time or space.

(1) is supposed to be fixed by #8486, I think. I will investigate why this is not the case.
(2) is a known limitation of Typescript's current semantics and architecture. See #9052 for an example.

[sandersn]

Actually, this is a duplicate of #6496. The issue is actually that npm link causes there to be two definitions of monet loaded. You can see this if you pass --traceResolution to the compiler:

======== Resolving module 'monet' from '/media/nathansa/src2/src/bug-sample-tsc-crash/use/src/index.ts'. ========
...
...
======== Module name 'monet' was successfully resolved to '/media/nathansa/src2/src/bug-sample-tsc-crash/use/node_modules/monet/index.d.ts'. ========
...
...
======== Resolving module 'monet' from '/home/nathansa/.nvm/versions/node/v7.4.0/lib/node_modules/@local/def/dist/index.d.ts'. ========
...
...
======== Module name 'monet' was successfully resolved to '/home/nathansa/.nvm/versions/node/v7.4.0/lib/node_modules/monet/index.d.ts'. ========

The first monet is the one that use got from running npm install. The second monet is the one that def get from running npm install followed by npm install g . monet. So the two Eithers are coming from two different monets. The workaround is to explicitly specify the path to use for monet when compiling def via baseUrl and paths:

{
  "compilerOptions": {
      "outDir": "dist",
      "baseUrl": ".",
      "paths": {
          "monet": ["node_modules/monet"]
      }
  },
  "include": [
    "./src/**/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

This will force both use/index.ts and the linked node_modules/@local/def/index.d.ts to resolve to node_modules/monet instead of the linked reference resolving to the global installation of monet.

[hiroshi-cl]

thanks for your investigation