Record type suggestion causes crash

[MarkDBlackwell]

Elm's documentation (located here) at elm-lang.org/docs/syntax#records says:

Records

dist {x,y} =                    -- pattern matching on fields
  sqrt (x^2 + y^2)

Now, in order to come up with a difficult or obscure portion of a type signature, I (usually) ask the Elm compiler to generate said portion. Often, I start with the obviously-wrong type of String, and let the compiler suggest what belongs in there.

BTW, generally (I suppose), if we comment out the entire type signature instead, then we withhold some helpful clues from the Elm compiler. So my code was:

type alias Artist =
    String

type alias Title =
    String

type alias SongComplex =
    { artist : Artist
    , title : Title
    , timestamp : String
    }

type alias SongSimple =
    { artist : Artist
    , title : Title
    }

song2SongSimple : String -> SongSimple
song2SongSimple { artist, title } =
    SongSimple
        artist
        title

Elm's error message was:

-- TYPE MISMATCH ------------------------------------------ [filename]

This record is causing problems in this pattern match.

188| song2SongSimple { artist, title } =
                       ^^^^^^^^^^^^^^^^^
The pattern matches things of type:

    String

But the values it will actually be trying to match are:

    { c | artist : a, title : b }

Therefore, in my code, I replaced String with the suggestion from the Elm compiler:

song2SongSimple : { c | artist : a, title : b } -> SongSimple
song2SongSimple { artist, title } =
    SongSimple
        artist
        title

Then Elm's error message was:

Processing multiple files...
[                                                  ] - 0 / 1elm-make.exe: It looks like something went wrong with the type inference algorithm.

Unable to generalize a type variable. It is not unranked.

Please create a minimal example that triggers this problem and report it to
<https://github.com/elm-lang/elm-compiler/issues>
elm-make.exe: thread blocked indefinitely in an MVar operation

BTW, I'm running Elm .18 on Git for Windows:

$ elm --version
0.18.0

$ bash --version
GNU bash, version 4.3.46(2)-release (i686-pc-msys)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

Later, after some experimentation in elm-repl, I tried commenting out the entire type signature. From the better, resulting Elm compiler suggestion, I learned that the portion (of the full type signature) replacing String actually should be:

{ a | artist : Artist, title : Title }

So, for fresh, Elm-newby minds such as mine, perhaps the Elm compiler's suggestion to replace String—appearing under the text, "But the values it will actually be trying to match are"—shouldn't be { c | artist : a, title : b }, but instead should be:

{ a | artist : String, title : String }