Definability checking is unconditionally flagging the use of a polymorphic
variable as an actual argument for a procedure reference in a PURE subprogram
unless the corresponding dummy is INTENT(IN). This isn't necessary, since
an INTENT(OUT) polymorphic dummy is already caught as an error in the definition
of the callee, which must also be PURE; and an INTENT(IN OUT) or intent-free
dummy is allowed to be passed a polymorphic actual in a PURE context, with
any attempt to deallocate it being caught in the callee.
So add a flag to the definability checker to disable the "polymorphic
definition in PURE context" check when using it to check actual arguments.
Differential Revision: https://reviews.llvm.org/D139044
The infrastructure in semantics that is used to check that the
left-hand sides of normal assignment statements are really definable
variables was not being used to check whether the LHSs of pointer assignments
are modifiable, and so most cases of unmodifiable pointers are left
undiagnosed. Rework the semantics checking for pointer assignments,
NULLIFY statements, pointer dummy arguments, &c. so that cases of
unmodifiable pointers are properly caught. This has been done
by extracting all the various definability checking code that has
been implemented for different contexts in Fortran into one new
facility.
The new consolidated definability checking code returns messages
meant to be attached as "because: " explanations to context-dependent
errors like "left-hand side of assignment is not definable".
These new error message texts and their attached explanations
affect many existing tests, which have been updated. The testing
infrastructure was extended by another patch to properly compare
warnings and explanatory messages, which had been ignored until
recently.
Differential Revision: https://reviews.llvm.org/D136979
