Implement a first-class error for reexported component functions #4348
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Currently I don't know how we can reasonably implement this. Given all the signatures of how we call functions and how functions are called on the host there's no real feasible way that I know of to hook these two up "seamlessly". This means that a component which reexports an imported function can't be run in Wasmtime. One of the main reasons for this is that when calling a component function Wasmtime wants to lower arguments first and then have them lifted when the host is called. With a reexport though there's not actually anything to lower into so we'd sort of need something similar to a table on the side or maybe a linear memory and that seems like it'd get quite complicated quite quickly for not really all that much benefit. As-such for now this simply returns a first-class error (rather than the current panic) in situations like this.
42 tasks
fitzgen
approved these changes
Jun 28, 2022
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Currently I don't know how we can reasonably implement this. Given all
the signatures of how we call functions and how functions are called on
the host there's no real feasible way that I know of to hook these two
up "seamlessly". This means that a component which reexports an imported
function can't be run in Wasmtime.
One of the main reasons for this is that when calling a component
function Wasmtime wants to lower arguments first and then have them
lifted when the host is called. With a reexport though there's not
actually anything to lower into so we'd sort of need something similar
to a table on the side or maybe a linear memory and that seems like it'd
get quite complicated quite quickly for not really all that much
benefit. As-such for now this simply returns a first-class error (rather
than the current panic) in situations like this.