Instead of modeling array initialization as a thin wrapper around tuple
initialization, handle it like a function call, with a return slot as
part of its input. This better matches how initialization via a call to
`ImplicitAs::Convert` will eventually work, and in particular lets us do
in-place initialization of arrays rather than always creating a
temporary.
This better reflects the purpose of these semantics nodes, and prepares
for adding TupleValue and TupleInit nodes to represent forming values
and initializers from literals.
In order to maintain diagnostic quality, add a mechanism to add notes to
any diagnostics that are produced as part of initialization of function
parameters. As suggested in review of #3205.
In passing, fix the only caller of `ImplicitAsRequired` outside of the
implementation of `Check::Context` to instead use
`ConvertToValueExpressionOfType`. This causes some missing
`value_binding` nodes to be added to the produced SemIR. Also fixed a
matching bug in lowering where a bogus load was being added, that
resulted in assertion failures when the checker bug was fixed.
The warning `-Wnon-virtual-dtor` starts producing false-positive
warnings after this change. Replace it with the fixed version,
`-Wdelete-non-virtual-dtor`.
IntegerLiterals are not signed, so get the zero-extended value rather
than the sign-extended value. Sometimes we use the high bit of the
`APInt`, though currently this only happens for the literals 8 and 9 due
to the way we convert decimal integers to binary.
Continuing along with #3070. Note this is just a file rename, with BUILD
edits; every file previously in semantics/ should show as moved (except
maybe BUILDs, which split).
Richard Smith
Jon Ross-Perkins