Matching on a single map element gives an UnsupportedOperationException

[joukestoel]

I would like to write a function definition containing a match on a map with a single element. Doing this however results in a UnsupportedOperationException when importing the module.

For example:

bool matched( (key:val) ) = true;

gives an UnsupportedOperationException when importing

Side note
Writing the code as follows:

bool matched( (key:_:val:_) ) = true;

gives an Ambiguous code error

[PaulKlint]

This is a very legitimate wish. Unfortunately map matching is not yet supported, see #290.
I close this one as duplicate.

[joukestoel]

Ah ok , I thought it would be a duplicate but I didn't find the other issue...

[PaulKlint]

But please turn your side note into s separate issue: "Ambiguous Rascal code"

[joukestoel]

Done! See #774