pointer indexing lowering requires an identifier

[resetius]

pointer indexing lowering requires an identifier

Status: Open.

Reproducer

An annotated TIndexExpr accepts any expression whose type is a pointer, but
lowering rejects a computed pointer collection such as an explicit cast:

(index (cast raw <ptr i32>) row)

The error is COLLECTION_NOT_ARRAY. Assigning the cast to a temporary and
indexing the identifier works:

(var values <ptr i32>)
(= values (cast raw <ptr i32>))
(index values row)

Cause

TAstLowerer::LowerLValueAddress and the TIndexExpr lowering path require
index->Collection to be TIdentExpr, even after type annotation has accepted
the collection as a pointer.

workaround

emit typed temporary pointer variables before all pointer indexing