latexdef which does not handle
--- as the operand. And
\texemdash is defined as a character. So that leaves me once again leaning on the collective wisdom of the group :)
There is no definition for
It's traditional that fonts define these ligatures (in addition to the f-ligatures)
T1 encoded fonts usually have also
Other ones may be defined on a font basis, but shouldn't concern the user.
TeX transforms the combinations at a very deep stage of processing, basically when it's putting characters one after another to form words and paragraphs, very much later than the stage where macros are expanded.