Compiler hangs when comparing functions with extensible records in type signature

[jfmengels]

Quick Summary: The following incorrect code causes the compiler to hang forever and grab more and more memory.

SSCCE

module CompilerError exposing (..)

type Thing b
    = Thing

changesTypeVariable : Thing { b | something : () } -> Thing { b | somethingElse : () }
changesTypeVariable _ =
    Thing

foo =
    if True then
        changesTypeVariable

    else
        identity

• Elm: 0.19.1
• Browser: NA
• Operating System: Linux Ubuntu 18.04

Additional Details

When I run this, I get to see Compiling ..., and then I need to kill the process because it hangs forever, and it also seems to take more and more memory endlessly.

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