forked from OSchip/llvm-project
124 lines
4.9 KiB
C++
124 lines
4.9 KiB
C++
//===--- Selection.h - What's under the cursor? -------------------*-C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// Many features are triggered at locations/ranges and operate on AST nodes.
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// (e.g. go-to-definition or code tweaks).
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// At a high level, such features need to work out which node is the correct
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// target.
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//
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// There are a few levels of ambiguity here:
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//
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// Which tokens are included:
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// int x = one + two; // what should "go to definition" do?
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// ^^^^^^
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//
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// Same token means multiple things:
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// string("foo") // class string, or a constructor?
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// ^
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//
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// Which level of the AST is interesting?
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// if (err) { // reference to 'err', or operator bool(),
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// ^ // or the if statement itself?
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//
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// Here we build and expose a data structure that allows features to resolve
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// these ambiguities in an appropriate way:
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// - we determine which low-level nodes are partly or completely covered
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// by the selection.
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// - we expose a tree of the selected nodes and their lexical parents.
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_SELECTION_H
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#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_SELECTION_H
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#include "clang/AST/ASTTypeTraits.h"
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#include "clang/AST/PrettyPrinter.h"
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#include "llvm/ADT/SmallVector.h"
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namespace clang {
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namespace clangd {
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class ParsedAST;
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// A selection can partially or completely cover several AST nodes.
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// The SelectionTree contains nodes that are covered, and their parents.
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// SelectionTree does not contain all AST nodes, rather only:
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// Decl, Stmt, TypeLoc, NestedNamespaceSpecifierLoc, CXXCtorInitializer.
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// (These are the nodes with source ranges that fit in DynTypedNode).
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//
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// Usually commonAncestor() is the place to start:
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// - it's the simplest answer to "what node is under the cursor"
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// - the selected Expr (for example) can be found by walking up the parent
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// chain and checking Node->ASTNode.
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// - if you want to traverse the selected nodes, they are all under
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// commonAncestor() in the tree.
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//
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// The SelectionTree owns the Node structures, but the ASTNode attributes
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// point back into the AST it was constructed with.
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class SelectionTree {
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public:
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// Creates a selection tree at the given byte offset in the main file.
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// This is approximately equivalent to a range of one character.
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// (Usually, the character to the right of Offset, sometimes to the left).
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SelectionTree(ASTContext &AST, unsigned Offset);
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// Creates a selection tree for the given range in the main file.
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// The range includes bytes [Start, End).
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// If Start == End, uses the same heuristics as SelectionTree(AST, Start).
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SelectionTree(ASTContext &AST, unsigned Start, unsigned End);
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// Describes to what extent an AST node is covered by the selection.
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enum Selection {
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// The AST node owns no characters covered by the selection.
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// Note that characters owned by children don't count:
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// if (x == 0) scream();
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// ^^^^^^
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// The IfStmt would be Unselected because all the selected characters are
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// associated with its children.
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// (Invisible nodes like ImplicitCastExpr are always unselected).
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Unselected,
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// The AST node owns selected characters, but is not completely covered.
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Partial,
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// The AST node owns characters, and is covered by the selection.
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Complete,
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};
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// An AST node that is implicated in the selection.
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// (Either selected directly, or some descendant is selected).
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struct Node {
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// The parent within the selection tree. nullptr for TranslationUnitDecl.
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Node *Parent;
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// Direct children within the selection tree.
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llvm::SmallVector<const Node *, 8> Children;
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// The corresponding node from the full AST.
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ast_type_traits::DynTypedNode ASTNode;
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// The extent to which this node is covered by the selection.
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Selection Selected;
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};
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// The most specific common ancestor of all the selected nodes.
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// If there is no selection, this is nullptr.
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const Node *commonAncestor() const;
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// The selection node corresponding to TranslationUnitDecl.
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// If there is no selection, this is nullptr.
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const Node *root() const { return Root; }
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private:
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std::deque<Node> Nodes; // Stable-pointer storage.
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const Node *Root;
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clang::PrintingPolicy PrintPolicy;
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void print(llvm::raw_ostream &OS, const Node &N, int Indent) const;
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friend llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
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const SelectionTree &T) {
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if (auto R = T.root())
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T.print(OS, *R, 0);
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else
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OS << "(empty selection)\n";
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return OS;
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}
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};
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} // namespace clangd
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} // namespace clang
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#endif
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