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//===--- TypeDifference.h - Utility for concrete type unification ---------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#include "Symbol.h"
#include "Term.h"
#include "swift/AST/Type.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include <optional>
#ifndef TYPE_DIFFERENCE_H_
#define TYPE_DIFFERENCE_H_
namespace llvm {
class raw_ostream;
} // end namespace llvm
namespace swift {
namespace rewriting {
class RewriteContext;
/// Describes transformations that turn LHS into RHS, given that there are a
/// pair of rules (BaseTerm.[LHS] => BaseTerm) and (BaseTerm.[RHS] => BaseTerm).
///
/// There are two kinds of transformations:
///
/// - Replacing a type term T1 with another type term T2, where T2 < T1.
/// - Replacing a type term T1 with a concrete type C2.
struct TypeDifference {
Term BaseTerm;
Symbol LHS;
Symbol RHS;
/// A pair (N1, N2) where N1 is an index into LHS.getSubstitutions() and
/// N2 is an index into RHS.getSubstitutions().
SmallVector<std::pair<unsigned, Term>, 1> SameTypes;
/// A pair (N1, C2) where N1 is an index into LHS.getSubstitutions() and
/// C2 is a concrete type symbol.
SmallVector<std::pair<unsigned, Symbol>, 1> ConcreteTypes;
TypeDifference(Term baseTerm, Symbol lhs, Symbol rhs,
SmallVector<std::pair<unsigned, Term>, 1> sameTypes,
SmallVector<std::pair<unsigned, Symbol>, 1> concreteTypes)
: BaseTerm(baseTerm), LHS(lhs), RHS(rhs),
SameTypes(sameTypes), ConcreteTypes(concreteTypes) {}
MutableTerm getOriginalSubstitution(unsigned index) const;
MutableTerm getReplacementSubstitution(unsigned index) const;
void dump(llvm::raw_ostream &out) const;
void verify(RewriteContext &ctx) const;
};
TypeDifference
buildTypeDifference(
Term baseTerm, Symbol symbol,
const llvm::SmallVector<std::pair<unsigned, Term>, 1> &sameTypes,
const llvm::SmallVector<std::pair<unsigned, Symbol>, 1> &concreteTypes,
RewriteContext &ctx);
} // end namespace rewriting
} // end namespace swift
#endif
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