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[TypeResolution] Ban local variable packs #66622

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Merged
merged 2 commits into from
Jun 16, 2023
Merged

[TypeResolution] Ban local variable packs #66622

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bab227d
Ban explicit local variable packs
Jun 14, 2023
5fbed1d
Ban inferred local variable packs
Jun 15, 2023
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7 changes: 7 additions & 0 deletions lib/Sema/TypeCheckStorage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -457,6 +457,13 @@ const PatternBindingEntry *PatternBindingEntryRequest::evaluate(
return &pbe;
}

// Local variable packs are not allowed.
if (binding->getDeclContext()->isLocalContext() &&
binding->getInit(entryNumber)->getType()->is<PackExpansionType>()) {
binding->diagnose(diag::expansion_not_allowed,
binding->getInit(entryNumber)->getType());
}

// A pattern binding at top level is not allowed to pick up another decl's
// opaque result type as its type by type inference.
if (!binding->getDeclContext()->isLocalContext() &&
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2 changes: 1 addition & 1 deletion lib/Sema/TypeCheckType.cpp
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Expand Up @@ -4617,7 +4617,7 @@ NeverNullType TypeResolver::resolvePackExpansionType(PackExpansionTypeRepr *repr
}

// We might not allow variadic expansions here at all.
if (!options.isPackExpansionSupported(getDeclContext())) {
if (!options.isPackExpansionSupported()) {
diagnose(repr->getLoc(), diag::expansion_not_allowed, result);
return ErrorType::get(ctx);
}
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7 changes: 1 addition & 6 deletions lib/Sema/TypeCheckType.h
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Expand Up @@ -335,20 +335,15 @@ class TypeResolutionOptions {
}

/// Whether pack expansion types are supported in this context.
bool isPackExpansionSupported(DeclContext *dc) const {
bool isPackExpansionSupported() const {
switch (context) {
case Context::FunctionInput:
case Context::VariadicFunctionInput:
case Context::PackElement:
case Context::TupleElement:
case Context::GenericArgument:
return true;

// Local variable packs are supported, but property packs
// are not.
case Context::PatternBindingDecl:
return !dc->isTypeContext();

case Context::None:
case Context::ProtocolGenericArgument:
case Context::Inherited:
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3 changes: 2 additions & 1 deletion test/Constraints/pack-expansion-expressions.swift
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Expand Up @@ -36,8 +36,9 @@ func coerceExpansion<each T>(_ value: repeat each T) {

func localValuePack<each T>(_ t: repeat each T) -> (repeat each T, repeat each T) {
let local = repeat each t
// expected-error@-1{{pack expansion 'repeat each T' can only appear in a function parameter list, tuple element, or generic argument list}}
let localAnnotated: repeat each T = repeat each t
// expected-error@-1{{value pack expansion can only appear inside a function argument list or tuple element}}
// expected-error@-1{{pack expansion 'repeat each T' can only appear in a function parameter list, tuple element, or generic argument list}}

return (repeat each local, repeat each localAnnotated)
}
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