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//===--- ConstraintGraphScope.h - Constraint Graph Scope --------*- C++ -*-===//
// This source file is part of the open source project
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
// See for license information
// See for the list of Swift project authors
// This file defines the \c ConstraintGraphScope class, an RAII object that
// introduces a new scope in which changes to the constraint graph are
// capture and will be reverted when the scope disappears.
namespace swift {
namespace constraints {
class ConstraintGraph;
/// RAII object that introduces a new constraint graph scope to capture
/// modifications made to the constraint graph.
/// Scopes are arranged in a stack, where the active scope is the top of the
/// stack. All changes made to the constraint graph are recorded in the
/// active scope. When the scope is popped (via the RAII object destructor),
/// those changes are reverted.
class ConstraintGraphScope {
ConstraintGraph &CG;
/// The parent scope, or null if this is the topmost scope.
ConstraintGraphScope *ParentScope;
/// The number of recorded changes that existed at the time this scope was
/// formed.
/// When this scope exits, any changes beyond this will be reverted to
/// bring the graph back to its state prior to the introduction of this
/// variable.
unsigned NumChanges;
ConstraintGraphScope(const ConstraintGraphScope&) = delete;
ConstraintGraphScope &operator=(const ConstraintGraphScope&) = delete;
explicit ConstraintGraphScope(ConstraintGraph &CG);
} // end namespace constraints
} // end namespace swift