check_m7.c textually included check.c, renamed three entry points aside, and
selected between two whole checkers by scanning each unit for `?`, `!`, `try`
and friends. A unit that mentioned any of them was checked by a second
implementation, so an M1-M6 rule fixed in check.c never reached it -- and the
split hid real defects, since the M7 half was reached by no existing fixture
until M7 cases were registered.
The split was cheaper to undo than it looked: every M7 dispatcher already
delegated to its M6 counterpart for nodes it did not handle. So the M7 entry
points become the single check_expr/check_stmt/check_lvalue/check_call, and
the former M6 bodies become check_expr_core/check_stmt_core/check_lvalue_core,
reached as the fallback. Recursion runs through the unified entry, which is
what makes an optional nested inside otherwise-M6 code get checked at all.
m7_check_fn and m7_check_method were identical to the M6 versions apart from
which check_stmt they called, so they are dropped. The feature scanner
(m7_type_ast, m7_node_feature, m7_program_feature) is gone with the dispatch
it fed, including the loop case that still consulted it. fe_check_program and
fe_check_expr_type keep the M7 bodies, which are supersets.
The build compiles check.c directly again.
No behaviour intended to change: the unified checker applies the union of the
rules to every unit, which for M1-M6 sources is what the M6 half already did.
coolguy
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