Parser: no kompile error when using undefined terms in RHS

[Denis Bogdanas]

The following definition compiles with no errors:

module ISSUE
  configuration <T> <k> .K </k> </T>
  syntax K  ::= "foo"
  rule foo => bar(.K)
endmodule

Although "bar" is not defined. If you try to run a program that activates the rule, it will throw NoSuchElementException: key not found: bar

This makes semantics definitions prone to typos.

Context: latest K version compiled on 26 Dec 2017.

[Radu Mereuta]

RHS doesn't matter:

module TEST
  configuration <T> <k> .K </k> </T>
  rule foo(.K) => bar(.K)
endmodule

If I remember correctly, K doesn't look to see if klabels are defined to ease the connection of external parsers.

[Denis Bogdanas]

Sorry for late reply. Thread got lost in some mail folders.

But this is not klabel. External parsers are supposed to use 'Foo(,,)-like notation for KLabels. Anything else should have syntax defined. Or I'm missing something?

[Dwight Guth]

So, this is not a well-formed K definition, because the bar klabel is not declared. K 4 changed the syntax of KLabels though, which is why bar now parses as a KLabel.

If you're frustrated by this, I would suggest upgrading to K 5, as we have fixed this issue. A fix for K 4 is very unlikely at this time.

[Denis Bogdanas]

Good to know, thanks!