The problem comes from the fact that macroOrTmpl[...] is transformed by
semSubscript which is trying to evaluate macroOrTmpl identifier in place. This
is okay for non-generic macros or templates, but wrong for generic ones, that
do not have a chance to receive their generic arguments explicitly specified in
brackets.
Solution:
1. macroOrTmpl[...] where macroOrTmpl is non-generic macro or template, then
macroOrTmpl is evaluated before applying brackets. (as before)
2. macroOrTmpl[...] where macroOrTmpl is generic macro or template, then if:
a. It comes from macroOrTmpl[...](...) call expr (efInCall), then macroOrTmpl
is turned into a symbol (efNoEvaluate) rather than evaluating it in place,
then whole bracket expr is returned to semIndirectOp which transforms it
to proper generic macro or template call with explicit generic arguments.
b. macroOrTmpl[...] does not come from call expr, as above macroOrTmpl is
transformed to symbol, then it is transformed into proper generic macro or
template call with explicit generic arguments and no normal arguments.
Turns out to be slightly problematic as `(int, int)` could be logically
thought of as an expression evaluating to a tuple value containing
two typedesc[int]s.
To disambiguate, the zero-tuple's type must still be written as
`tuple[]`, and what would be tuple value expressions containing only
typedescs are interpreted as types.
() # value of type `tuple[]`
(int, int) # tuple type
(int, int, ()) # value of type `(typedesc[int], typedesc[int], tuple[])`
