Very slow incremental compilation (tsc --watch)

[MarkChrisLevy]

TypeScript Version: 1.8.0 / nightly (2.0.0-dev.201xxxxx)
2.0.3
Code
I see massive slow down in incremental compilation (tsc --watch). Change in one file takes 9-10 (or even more) seconds to compile, in 1.8 was much much faster.

Our project is Angular2/Ionic2 app. We made a switch to newest release of Ionic, which uses latest Angular2.

I just made a simple test. Created new file (test.ts), with class declaration class A {prop: number} and added to my project. I run tsc --watch --traceResolution and after initial compilation I made a change in test.ts - thanks to trace resolution I've noticed, that compiler is checking all the files in my project and trying to resolve modules, that are used in those files. Obviously that takes time - I don't know whether that should work like this and if that didn't change from 1.8, but it looks a bit weird.

Expected behavior:
Incremental compilation should work fast, compiling only changed file and possibly files, that are some way related to that file.

Actual behavior:
Compilation of a file (with one line of code, no imports, no exports) takes many seconds (9-15 sec).

[MarkChrisLevy]

Duplicate of #10018.