Improve trimmability of string interpolation - #62844
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The vararg methods `print(io, xs...)`, `print_to_string` and
`string_with_env` printed their arguments with `for x in xs`. That loop
variable is a phi node merging the type of the first element with the
union of the rest, and inference widens such a union to `Any` once it
has more than three members, so every `print(io, x)` in the loop became
a dynamic dispatch. Under `juliac --trim=safe`, which compiles these
methods for their exact argument types, any interpolated string whose
arguments spanned more than three distinct types was rejected as an
unresolved call, e.g. `"got $(r) vs $(i) with $(x) and $(s)"`.
Indexing the tuple instead (`xs[i]`) keeps the exact union of element
types, which union-splits into statically resolved calls regardless of
how many members it has.
This helps only for exact unions; `Vararg{Any}` is still not trimmable.
Assisted-by: Claude Code (Fable 5)
timholy
added
compiler:inference
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The vararg methods
print(io, xs...),print_to_stringandstring_with_envprinted their arguments withfor x in xs. That loop variable is a phi node merging the type of the first element with the union of the rest, and inference widens such a union toAnyonce it has more than three members, so everyprint(io, x)in the loop became a dynamic dispatch. Underjuliac --trim=safe, which compiles these methods for their exact argument types, any interpolated string whose arguments spanned more than three distinct types was rejected as an unresolved call, e.g."got $(r) vs $(i) with $(x) and $(s)".Indexing the tuple instead (
xs[i]) keeps the exact union of element types, which union-splits into statically resolved calls regardless of how many members it has.This helps only for exact unions;
Vararg{Any}is still not trimmable.Assisted-by: Claude Code (Fable 5)