This change adds a `BindSymbolicName` instruction for generic bindings,
paralleling the existing `BindName`. A mechanism is also added to allow
both kinds of binding to be accessed uniformly, for convenience in the
case where the two different kinds of binding are treated the same.
Generic bindings of type `type` are allowed to be used as types,
although no operations are provided for such types. For now lowering
treats these types as empty structs, which seems like a reasonable
lowering for non-monomorphized unconstrained types.
Trust semantics to have put them in the right places.
Many parts of lowering still need to be updated to use the value
representation chosen at the semantics layer, but this is an incremental
step towards that.
This implements initializing expression semantics for structs and
tuples, following #2006 and discussions since.
Tuple and (and analogously, struct) literals are treated as having a
mixed expression category that is later resolved based on how the
literal is used, as either a tuple initializer or a tuple value, at
which point we create a `TupleInit` or `TupleValue` that represents the
formation of the tuple initializer or tuple value from the tuple
literal.
There's quite a lot of TODOs here, and the SemIR representation is still
not quite right, but this seems like a good place to checkpoint some
incremental progress.
Richard Smith
Jon Ross-Perkins