[moveOnly] Allow the @_noImplicitCopy decl attribute to be applied to parameters #39991
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gottesmm
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The bug before was that in deserialization I did not shift by the right amount. Its fixed now. |
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…mplicitCopy argument. I am purposely doing this in SILGen rather than at the type system level to avoid having to have to add a bunch of boilerplate to the type system. Instead of doing that, I am in SILGen checking for the isNoImplicitCopy bit on the ParamDecl when we emit arguments. At that point, I set on the specific SILArgument being emitted the bit that it is no implicit copy. In terms of printing at the SIL level, I just printed it in front of the function argument type like @owned, e.x.: func myFunc(_ x: @_noImplicitCopy T) -> T { ... } becomes: bb0(%0 : @noImplicitCopy @owned $T): Some notes: * Just to be explicit, I am making it so that no implicit copy parameters by default are always passed at +1. The reason why I think this makes sense is that this is the natural way of working with a move only value. * As always, one can not write no implicit copy the attribute without passing the flag -enable-experimental-move-only so this is NFC. rdar://83957088
…ssed at +1 by default.
…in such a form that move checking works on it. This means that one can pass around let moveOnly values using @_noImplicitCopy.
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By mistake pushed main instead of my branch X ). |
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gottesmm
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Nov 1, 2021
| @@ -83,7 +83,7 @@ class MyGenericClass<T> { | |||
| return nil | |||
| } | |||
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| func foo(@_noImplicitCopy _ t: T) { // expected-error {{@_noImplicitCopy may only be used on 'var' declarations}} | |||
| func foo(@_noImplicitCopy _ t: T) { | |||
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NOTE: The error for using this on a generic parameter is a SILGen error, not a semi error, so it is in the SILGen test that I added. This is b/c the type checker doesn't have enough information to distinguish in between a type that contains a generic type and a type that just has a type parameter (consider UnsafePointer, a loadable type at the SIL level despite the type parameter at the AST level).
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Again, this is all behind a flag, so it shouldn't effect normal codegen. |
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Everything in this PR can only be used if one passes in the flag -enable-experimental-move-only.
Marking a parameter with this attribute looks as follows:
operationally this has the following effects:
This lets one now create whole call trees by passing @_noImplicitCopy lets as @_noImplicitCopy arguments.
rdar://83957088