[ASTImporter] Move structural equivalence context to its own file. NFCI

Create a header and impl file for the structural equivalence context.
This is to allow other users outside clang importer. NFCI

Differential Revision: https://reviews.llvm.org/D31777

rdar://problem/30167717

llvm-svn: 301604

clang/include/clang/AST/ASTStructuralEquivalence.h

@@ -0,0 +1,101 @@
+//===--- ASTStructuralEquivalence.h - ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the StructuralEquivalenceContext class which checks for
+//  structural equivalence between types.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H
+#define LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/Optional.h"
+#include <deque>
+
+namespace clang {
+
+class ASTContext;
+class Decl;
+class DiagnosticBuilder;
+class QualType;
+class RecordDecl;
+class SourceLocation;
+
+struct StructuralEquivalenceContext {
+  /// AST contexts for which we are checking structural equivalence.
+  ASTContext &FromCtx, &ToCtx;
+
+  /// The set of "tentative" equivalences between two canonical
+  /// declarations, mapping from a declaration in the first context to the
+  /// declaration in the second context that we believe to be equivalent.
+  llvm::DenseMap<Decl *, Decl *> TentativeEquivalences;
+
+  /// Queue of declarations in the first context whose equivalence
+  /// with a declaration in the second context still needs to be verified.
+  std::deque<Decl *> DeclsToCheck;
+
+  /// Declaration (from, to) pairs that are known not to be equivalent
+  /// (which we have already complained about).
+  llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls;
+
+  /// Whether we're being strict about the spelling of types when
+  /// unifying two types.
+  bool StrictTypeSpelling;
+
+  /// Whether warn or error on tag type mismatches.
+  bool ErrorOnTagTypeMismatch;
+
+  /// Whether to complain about failures.
+  bool Complain;
+
+  /// \c true if the last diagnostic came from ToCtx.
+  bool LastDiagFromC2;
+
+  StructuralEquivalenceContext(
+      ASTContext &FromCtx, ASTContext &ToCtx,
+      llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls,
+      bool StrictTypeSpelling = false, bool Complain = true)
+      : FromCtx(FromCtx), ToCtx(ToCtx), NonEquivalentDecls(NonEquivalentDecls),
+        StrictTypeSpelling(StrictTypeSpelling), Complain(Complain),
+        LastDiagFromC2(false) {}
+
+  DiagnosticBuilder Diag1(SourceLocation Loc, unsigned DiagID);
+  DiagnosticBuilder Diag2(SourceLocation Loc, unsigned DiagID);
+
+  /// Determine whether the two declarations are structurally
+  /// equivalent.
+  bool IsStructurallyEquivalent(Decl *D1, Decl *D2);
+
+  /// Determine whether the two types are structurally equivalent.
+  bool IsStructurallyEquivalent(QualType T1, QualType T2);
+
+  /// Find the index of the given anonymous struct/union within its
+  /// context.
+  ///
+  /// \returns Returns the index of this anonymous struct/union in its context,
+  /// including the next assigned index (if none of them match). Returns an
+  /// empty option if the context is not a record, i.e.. if the anonymous
+  /// struct/union is at namespace or block scope.
+  ///
+  /// FIXME: This is needed by ASTImporter and ASTStructureEquivalence. It
+  /// probably makes more sense in some other common place then here.
+  static llvm::Optional<unsigned>
+  findUntaggedStructOrUnionIndex(RecordDecl *Anon);
+
+private:
+  /// Finish checking all of the structural equivalences.
+  ///
+  /// \returns true if an error occurred, false otherwise.
+  bool Finish();
+};
+} // namespace clang
+
+#endif // LLVM_CLANG_AST_ASTSTRUCTURALEQUIVALENCE_H