1//===--- LexicallyOrderedRecursiveASTVisitor.h - ----------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the LexicallyOrderedRecursiveASTVisitor interface, which
10// recursively traverses the entire AST in a lexical order.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H
15#define LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H
16
17#include "clang/AST/RecursiveASTVisitor.h"
18#include "clang/Basic/LLVM.h"
19#include "clang/Basic/SourceManager.h"
20#include "llvm/Support/SaveAndRestore.h"
21
22namespace clang {
23
24/// A RecursiveASTVisitor subclass that guarantees that AST traversal is
25/// performed in a lexical order (i.e. the order in which declarations are
26/// written in the source).
27///
28/// RecursiveASTVisitor doesn't guarantee lexical ordering because there are
29/// some declarations, like Objective-C @implementation declarations
30/// that might be represented in the AST differently to how they were written
31/// in the source.
32/// In particular, Objective-C @implementation declarations may contain
33/// non-Objective-C declarations, like functions:
34///
35/// @implementation MyClass
36///
37/// - (void) method { }
38/// void normalFunction() { }
39///
40/// @end
41///
42/// Clang's AST stores these declarations outside of the @implementation
43/// declaration, so the example above would be represented using the following
44/// AST:
45/// |-ObjCImplementationDecl ... MyClass
46/// | `-ObjCMethodDecl ... method
47/// | ...
48/// `-FunctionDecl ... normalFunction
49/// ...
50///
51/// This class ensures that these declarations are traversed before the
52/// corresponding TraverseDecl for the @implementation returns. This ensures
53/// that the lexical parent relationship between these declarations and the
54/// @implementation is preserved while traversing the AST. Note that the
55/// current implementation doesn't mix these declarations with the declarations
56/// contained in the @implementation, so the traversal of all of the
57/// declarations in the @implementation still doesn't follow the lexical order.
58template <typename Derived>
59class LexicallyOrderedRecursiveASTVisitor
60 : public RecursiveASTVisitor<Derived> {
61 using BaseType = RecursiveASTVisitor<Derived>;
62
63public:
64 LexicallyOrderedRecursiveASTVisitor(const SourceManager &SM) : SM(SM) {}
65
66 bool TraverseObjCImplementationDecl(ObjCImplementationDecl *D) {
67 // Objective-C @implementation declarations should not trigger early exit
68 // until the additional decls are traversed as their children are not
69 // lexically ordered.
70 bool Result = BaseType::TraverseObjCImplementationDecl(D);
71 return TraverseAdditionalLexicallyNestedDeclarations() ? Result : false;
72 }
73
74 bool TraverseObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
75 bool Result = BaseType::TraverseObjCCategoryImplDecl(D);
76 return TraverseAdditionalLexicallyNestedDeclarations() ? Result : false;
77 }
78
79 bool TraverseDeclContextHelper(DeclContext *DC) {
80 if (!DC)
81 return true;
82
83 for (auto I = DC->decls_begin(), E = DC->decls_end(); I != E;) {
84 Decl *Child = *I;
85 if (BaseType::canIgnoreChildDeclWhileTraversingDeclContext(Child)) {
86 ++I;
87 continue;
88 }
89 if (!isa<ObjCImplementationDecl>(Val: Child) &&
90 !isa<ObjCCategoryImplDecl>(Val: Child)) {
91 if (!BaseType::getDerived().TraverseDecl(Child))
92 return false;
93 ++I;
94 continue;
95 }
96 // Gather declarations that follow the Objective-C implementation
97 // declarations but are lexically contained in the implementation.
98 LexicallyNestedDeclarations.clear();
99 for (++I; I != E; ++I) {
100 Decl *Sibling = *I;
101 if (!SM.isBeforeInTranslationUnit(LHS: Sibling->getBeginLoc(),
102 RHS: Child->getEndLoc()))
103 break;
104 if (!BaseType::canIgnoreChildDeclWhileTraversingDeclContext(Sibling))
105 LexicallyNestedDeclarations.push_back(Elt: Sibling);
106 }
107 if (!BaseType::getDerived().TraverseDecl(Child))
108 return false;
109 }
110 return true;
111 }
112
113 Stmt::child_range getStmtChildren(Stmt *S) { return S->children(); }
114
115 SmallVector<Stmt *, 8> getStmtChildren(CXXOperatorCallExpr *CE) {
116 SmallVector<Stmt *, 8> Children(CE->children());
117 bool Swap;
118 // Switch the operator and the first operand for all infix and postfix
119 // operations.
120 switch (CE->getOperator()) {
121 case OO_Arrow:
122 case OO_Call:
123 case OO_Subscript:
124 Swap = true;
125 break;
126 case OO_PlusPlus:
127 case OO_MinusMinus:
128 // These are postfix unless there is exactly one argument.
129 Swap = Children.size() != 2;
130 break;
131 default:
132 Swap = CE->isInfixBinaryOp();
133 break;
134 }
135 if (Swap && Children.size() > 1)
136 std::swap(a&: Children[0], b&: Children[1]);
137 return Children;
138 }
139
140private:
141 bool TraverseAdditionalLexicallyNestedDeclarations() {
142 // FIXME: Ideally the gathered declarations and the declarations in the
143 // @implementation should be mixed and sorted to get a true lexical order,
144 // but right now we only care about getting the correct lexical parent, so
145 // we can traverse the gathered nested declarations after the declarations
146 // in the decl context.
147 assert(!BaseType::getDerived().shouldTraversePostOrder() &&
148 "post-order traversal is not supported for lexically ordered "
149 "recursive ast visitor");
150 for (Decl *D : LexicallyNestedDeclarations) {
151 if (!BaseType::getDerived().TraverseDecl(D))
152 return false;
153 }
154 return true;
155 }
156
157 const SourceManager &SM;
158 llvm::SmallVector<Decl *, 8> LexicallyNestedDeclarations;
159};
160
161} // end namespace clang
162
163#endif // LLVM_CLANG_AST_LEXICALLYORDEREDRECURSIVEASTVISITOR_H
164

source code of clang/include/clang/AST/LexicallyOrderedRecursiveASTVisitor.h