The parsing of I/O units uses look-ahead to discriminate between
keywords, variables and expressions as part of distinguishing internal
from external I/O. The look-ahead was inaccurate for variables that
appear as the initial parts of expressions.
Differential Revision: https://reviews.llvm.org/D95743
READ(CVAR)[,item-list] with a character variable CVAR
could be parsed as an unformatted READ from an internal
unit or as a formatted READ from the default external unit
with a needlessly parenthesized variable format. We parse
it as the former, but Fortran doesn't have unformatted
internal I/O.
Differential revision: https://reviews.llvm.org/D90493
peter klausler