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3749a98763
This commit adds tracking of the reason a declaration reference is potentially unavailable to the UnavailableToOptionalExpr AST node and to OverloadChoice. We will use this reason during SILGen to emit the appropriate run-time check and during typechecking to provide more helpful diagnostics. To keep OverloadChoice as small as possible, we encode the reason as an index into a vector of reasons stored in a given instance of ConstraintSystem (this is the same approach that Fix takes). This commit adds Sema/OverloadChoice.cpp (for the parts of OverloadChoice that now rely on ConstraintSystem) and AST/Availability.h (to bring in availability-related structures without TypeRefinementContext). Swift SVN r22377
62 lines
2.3 KiB
C++
62 lines
2.3 KiB
C++
//===--- OverloadChoice.cpp - A Choice from an Overload Set ----*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// This file provides the \c OverloadChoice class and its related types,
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// which is used by the constraint-based type checker to describe the
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// selection of a particular overload from a set.
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//
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//===----------------------------------------------------------------------===//
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#include "OverloadChoice.h"
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#include "ConstraintSystem.h"
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#include "swift/AST/Availability.h"
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using namespace swift;
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using namespace constraints;
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OverloadChoice::OverloadChoice(
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Type base, ValueDecl *value, bool isSpecialized, ConstraintSystem &CS,
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const Optional<UnavailabilityReason> &reasonUnavailable)
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: BaseAndBits(base, isSpecialized ? IsSpecializedBit : 0) {
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assert((reinterpret_cast<uintptr_t>(value) & (uintptr_t)0x03) == 0 &&
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"Badly aligned decl");
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DeclOrKind = reinterpret_cast<uintptr_t>(value);
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UnavailableReasonData = compactUnavailableReasonData(CS, reasonUnavailable);
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}
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uint16_t OverloadChoice::compactUnavailableReasonData(
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ConstraintSystem &CS, const Optional<UnavailabilityReason> &reason) {
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// A value of 0 indicates no reason (that is, that the overload choice is
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// always available).
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if (!reason.hasValue()) {
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return 0;
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}
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// If there is a reason, we add it to UnavailabilityReasons and encode the
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// index in our compact representation. We could get more fancy here by
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// hashing the reason but, for the moment, we take a similar approach to that
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// that taken by Fix.
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unsigned index = CS.UnavailabilityReasons.size();
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CS.UnavailabilityReasons.push_back(reason.getValue());
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// Encode the reason as the index into UnavailabilityReasons + 1.
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return index + 1;
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}
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const UnavailabilityReason &
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OverloadChoice::getReasonUnavailable(ConstraintSystem &CS) const {
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assert(UnavailableReasonData != 0);
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unsigned index = UnavailableReasonData - 1;
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return CS.UnavailabilityReasons[index];
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}
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