A cast of an untyped deref reads at native width

Found by the Pascal cross-target differential (the test corpus, pxx x86-64 as the reference, FPC as the third arm): test_cast_as_lvalue_builtin_names' Int64(p^) row differed on i386, arm32 and riscv32. Widening the probe to the float kinds showed the same defect wrong on the 64-bit targets too.

Resolution (2026-09-28)

An untyped p^ is an AN_DEREF tagged tyUnknown, and an untyped parameter is declared tyPointer by reference; each backend loaded either at native width and the cast then CONVERTED that value. FPC reinterprets the memory at the cast's width. TryScalarNamedCast, the shared construction half of every named scalar cast, now stamps an untyped deref with the cast's kind, and rewrites an untyped parameter into the PT(@v)^ deref that FinishCastAsLValueStore already builds for the store side -- one shape for the read and the write.

Fixture test/test_a_cast_of_an_untyped_deref_reads_at_the_casts_width.pas (Int64/QWord/LongInt/Word/Byte/Double/Single/enum over p^, in an expression, an assignment, a comparison, a store; const Int64/QWord/Double and a var read-modify-write through untyped parameters; .expected by FPC 3.2.2), in test-core native and i386/aarch64/arm32/riscv32. v446: 3 rows wrong on the 64-bit targets, 11 on the 32-bit ones; this build none.