LSP: Implements goto-definition.

libsolidity/CMakeLists.txt

@@ -155,10 +155,10 @@ set(sources
 	interface/StorageLayout.h
 	interface/Version.cpp
 	interface/Version.h
-	lsp/LanguageServer.cpp
-	lsp/LanguageServer.h
 	lsp/FileRepository.cpp
 	lsp/FileRepository.h
+	lsp/GotoDefinition.cpp
+	lsp/GotoDefinition.h
 	lsp/HandlerBase.cpp
 	lsp/HandlerBase.h
 	lsp/LanguageServer.cpp

libsolidity/ast/ASTUtils.cpp

@@ -18,12 +18,35 @@
 
 #include <libsolidity/ast/AST.h>
 #include <libsolidity/ast/ASTUtils.h>
+#include <libsolidity/ast/ASTVisitor.h>
 
 #include <libsolutil/Algorithms.h>
 
 namespace solidity::frontend
 {
 
+ASTNode const* locateInnermostASTNode(int _offsetInFile, SourceUnit const& _sourceUnit)
+{
+	ASTNode const* innermostMatch = nullptr;
+	auto locator = SimpleASTVisitor(
+		[&](ASTNode const& _node) -> bool
+		{
+			// In the AST parent location always covers the whole child location.
+			// The parent is visited first so to get the innermost node we simply
+			// take the last one that still contains the offset.
+
+			if (!_node.location().containsOffset(_offsetInFile))
+				return false;
+
+			innermostMatch = &_node;
+			return true;
+		},
+		[](ASTNode const&) {}
+	);
+	_sourceUnit.accept(locator);
+	return innermostMatch;
+}
+
 bool isConstantVariableRecursive(VariableDeclaration const& _varDecl)
 {
 	solAssert(_varDecl.isConstant(), "Constant variable expected");

libsolidity/ast/ASTUtils.h

@@ -21,9 +21,11 @@
 namespace solidity::frontend
 {
 
-class VariableDeclaration;
+class ASTNode;
 class Declaration;
 class Expression;
+class SourceUnit;
+class VariableDeclaration;
 
 /// Find the topmost referenced constant variable declaration when the given variable
 /// declaration value is an identifier. Works only for constant variable declarations.
@@ -33,4 +35,7 @@ VariableDeclaration const* rootConstVariableDeclaration(VariableDeclaration cons
 /// Returns true if the constant variable declaration is recursive.
 bool isConstantVariableRecursive(VariableDeclaration const& _varDecl);
 
+/// Returns the innermost AST node that covers the given location or nullptr if not found.
+ASTNode const* locateInnermostASTNode(int _offsetInFile, SourceUnit const& _sourceUnit);
+
 }

libsolidity/lsp/GotoDefinition.cpp

@@ -0,0 +1,66 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+#include <libsolidity/lsp/GotoDefinition.h>
+#include <libsolidity/lsp/Transport.h> // for RequestError
+#include <libsolidity/lsp/Utils.h>
+#include <libsolidity/ast/AST.h>
+#include <libsolidity/ast/ASTUtils.h>
+
+#include <fmt/format.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace solidity::frontend;
+using namespace solidity::langutil;
+using namespace solidity::lsp;
+using namespace std;
+
+void GotoDefinition::operator()(MessageID _id, Json::Value const& _args)
+{
+	auto const [sourceUnitName, lineColumn] = extractSourceUnitNameAndLineColumn(_args);
+
+	ASTNode const* sourceNode = m_server.astNodeAtSourceLocation(sourceUnitName, lineColumn);
+
+	vector<SourceLocation> locations;
+	if (auto const* expression = dynamic_cast<Expression const*>(sourceNode))
+	{
+		// Handles all expressions that can have one or more declaration annotation.
+		if (auto const* declaration = referencedDeclaration(expression))
+			if (auto location = declarationLocation(declaration))
+				locations.emplace_back(move(location.value()));
+	}
+	else if (auto const* identifierPath = dynamic_cast<IdentifierPath const*>(sourceNode))
+	{
+		if (auto const* declaration = identifierPath->annotation().referencedDeclaration)
+			if (auto location = declarationLocation(declaration))
+				locations.emplace_back(move(location.value()));
+	}
+	else if (auto const* importDirective = dynamic_cast<ImportDirective const*>(sourceNode))
+	{
+		auto const& path = *importDirective->annotation().absolutePath;
+		if (fileRepository().sourceUnits().count(path))
+			locations.emplace_back(SourceLocation{0, 0, make_shared<string const>(path)});
+	}
+
+	Json::Value reply = Json::arrayValue;
+	for (SourceLocation const& location: locations)
+		reply.append(toJson(location));
+	client().reply(_id, reply);
+}

libsolidity/lsp/GotoDefinition.h

@@ -0,0 +1,31 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+#include <libsolidity/lsp/HandlerBase.h>
+
+namespace solidity::lsp
+{
+
+class GotoDefinition: public HandlerBase
+{
+public:
+	explicit GotoDefinition(LanguageServer& _server): HandlerBase(_server) {}
+
+	void operator()(MessageID, Json::Value const&);
+};
+
+}

libsolidity/lsp/HandlerBase.cpp

@@ -1,3 +1,22 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+#include <libsolutil/Exceptions.h>
+
 #include <libsolidity/lsp/HandlerBase.h>
 #include <libsolidity/lsp/LanguageServer.h>
 #include <libsolidity/lsp/Utils.h>
@@ -5,13 +24,13 @@
 
 #include <liblangutil/Exceptions.h>
 
+#include <fmt/format.h>
+
+using namespace solidity::langutil;
+using namespace solidity::lsp;
+using namespace solidity::util;
 using namespace std;
 
-namespace solidity::lsp
-{
-
-using namespace langutil;
-
 Json::Value HandlerBase::toRange(SourceLocation const& _location) const
 {
 	if (!_location.hasText())
@@ -33,31 +52,27 @@ Json::Value HandlerBase::toJson(SourceLocation const& _location) const
 	return item;
 }
 
-optional<SourceLocation> HandlerBase::parsePosition(string const& _sourceUnitName, Json::Value const& _position) const
+pair<string, LineColumn> HandlerBase::extractSourceUnitNameAndLineColumn(Json::Value const& _args) const
 {
-	if (!fileRepository().sourceUnits().count(_sourceUnitName))
-		return nullopt;
+	string const uri = _args["textDocument"]["uri"].asString();
+	string const sourceUnitName = fileRepository().clientPathToSourceUnitName(uri);
+	if (!fileRepository().sourceUnits().count(sourceUnitName))
+		BOOST_THROW_EXCEPTION(
+			RequestError(ErrorCode::RequestFailed) <<
+			errinfo_comment("Unknown file: " + uri)
+		);
 
-	if (optional<LineColumn> lineColumn = parseLineColumn(_position))
-		if (optional<int> const offset = CharStream::translateLineColumnToPosition(
-			fileRepository().sourceUnits().at(_sourceUnitName),
-			*lineColumn
-		))
-			return SourceLocation{*offset, *offset, make_shared<string>(_sourceUnitName)};
-	return nullopt;
-}
-
-optional<SourceLocation> HandlerBase::parseRange(string const& _sourceUnitName, Json::Value const& _range) const
-{
-	if (!_range.isObject())
-		return nullopt;
-	optional<SourceLocation> start = parsePosition(_sourceUnitName, _range["start"]);
-	optional<SourceLocation> end = parsePosition(_sourceUnitName, _range["end"]);
-	if (!start || !end)
-		return nullopt;
-	solAssert(*start->sourceName == *end->sourceName);
-	start->end = end->end;
-	return start;
-}
+	auto const lineColumn = parseLineColumn(_args["position"]);
+	if (!lineColumn)
+		BOOST_THROW_EXCEPTION(
+			RequestError(ErrorCode::RequestFailed) <<
+			errinfo_comment(fmt::format(
+				"Unknown position {line}:{column} in file: {file}",
+				fmt::arg("line", lineColumn.value().line),
+				fmt::arg("column", lineColumn.value().column),
+				fmt::arg("file", sourceUnitName)
+			))
+		);
 
+	return {sourceUnitName, *lineColumn};
 }

libsolidity/lsp/HandlerBase.h

@@ -1,3 +1,20 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
 #pragma once
 
 #include <libsolidity/lsp/FileRepository.h>
@@ -24,22 +41,15 @@ public:
 	Json::Value toRange(langutil::SourceLocation const& _location) const;
 	Json::Value toJson(langutil::SourceLocation const& _location) const;
 
-	std::optional<langutil::SourceLocation> parsePosition(
-		std::string const& _sourceUnitName,
-		Json::Value const& _position
-	) const;
+	/// @returns source unit name and the line column position as extracted
+	/// from the JSON-RPC parameters.
+	std::pair<std::string, langutil::LineColumn> extractSourceUnitNameAndLineColumn(Json::Value const& _params) const;
 
-	/// @returns the source location given a source unit name and an LSP Range object,
-	/// or nullopt on failure.
-	std::optional<langutil::SourceLocation> parseRange(
-		std::string const& _sourceUnitName,
-		Json::Value const& _range
-	) const;
-
-	langutil::CharStreamProvider const& charStreamProvider() const noexcept { return m_server.charStreamProvider(); };
-	FileRepository const& fileRepository() const noexcept { return m_server.fileRepository(); };
-	Transport& client() const noexcept { return m_server.client(); };
+	langutil::CharStreamProvider const& charStreamProvider() const noexcept { return m_server.charStreamProvider(); }
+	FileRepository const& fileRepository() const noexcept { return m_server.fileRepository(); }
+	Transport& client() const noexcept { return m_server.client(); }
 
+protected:
 	LanguageServer& m_server;
 };
 

libsolidity/lsp/LanguageServer.cpp

@@ -24,6 +24,8 @@
 #include <libsolidity/lsp/HandlerBase.h>
 #include <libsolidity/lsp/Utils.h>
 
+// LSP feature implementations
+#include <libsolidity/lsp/GotoDefinition.h>
 
 #include <liblangutil/SourceReferenceExtractor.h>
 #include <liblangutil/CharStream.h>
@@ -75,9 +77,11 @@ LanguageServer::LanguageServer(Transport& _transport):
 		{"initialize", bind(&LanguageServer::handleInitialize, this, _1, _2)},
 		{"initialized", [](auto, auto) {}},
 		{"shutdown", [this](auto, auto) { m_state = State::ShutdownRequested; }},
+		{"textDocument/definition", GotoDefinition(*this) },
 		{"textDocument/didOpen", bind(&LanguageServer::handleTextDocumentDidOpen, this, _2)},
 		{"textDocument/didChange", bind(&LanguageServer::handleTextDocumentDidChange, this, _2)},
 		{"textDocument/didClose", bind(&LanguageServer::handleTextDocumentDidClose, this, _2)},
+		{"textDocument/implementation", GotoDefinition(*this) },
 		{"workspace/didChangeConfiguration", bind(&LanguageServer::handleWorkspaceDidChangeConfiguration, this, _2)},
 	},
 	m_fileRepository("/" /* basePath */),
@@ -85,11 +89,6 @@ LanguageServer::LanguageServer(Transport& _transport):
 {
 }
 
-optional<SourceLocation> LanguageServer::parseRange(string const& _sourceUnitName, Json::Value const& _range)
-{
-	return HandlerBase{*this}.parseRange(_sourceUnitName, _range);
-}
-
 Json::Value LanguageServer::toRange(SourceLocation const& _location)
 {
 	return HandlerBase(*this).toRange(_location);
@@ -258,8 +257,10 @@ void LanguageServer::handleInitialize(MessageID _id, Json::Value const& _args)
 	Json::Value replyArgs;
 	replyArgs["serverInfo"]["name"] = "solc";
 	replyArgs["serverInfo"]["version"] = string(VersionNumber);
-	replyArgs["capabilities"]["textDocumentSync"]["openClose"] = true;
+	replyArgs["capabilities"]["definitionProvider"] = true;
+	replyArgs["capabilities"]["implementationProvider"] = true;
 	replyArgs["capabilities"]["textDocumentSync"]["change"] = 2; // 0=none, 1=full, 2=incremental
+	replyArgs["capabilities"]["textDocumentSync"]["openClose"] = true;
 
 	m_client.reply(_id, move(replyArgs));
 }
@@ -313,7 +314,7 @@ void LanguageServer::handleTextDocumentDidChange(Json::Value const& _args)
 		string text = jsonContentChange["text"].asString();
 		if (jsonContentChange["range"].isObject()) // otherwise full content update
 		{
-			optional<SourceLocation> change = parseRange(sourceUnitName, jsonContentChange["range"]);
+			optional<SourceLocation> change = parseRange(m_fileRepository, sourceUnitName, jsonContentChange["range"]);
 			lspAssert(
 				change && change->hasText(),
 				ErrorCode::RequestFailed,
@@ -346,7 +347,7 @@ void LanguageServer::handleTextDocumentDidClose(Json::Value const& _args)
 	compileAndUpdateDiagnostics();
 }
 
-ASTNode const* LanguageServer::requestASTNode(std::string const& _sourceUnitName, LineColumn const& _filePos)
+ASTNode const* LanguageServer::astNodeAtSourceLocation(std::string const& _sourceUnitName, LineColumn const& _filePos)
 {
 	if (m_compilerStack.state() < CompilerStack::AnalysisPerformed)
 		return nullptr;
@@ -354,11 +355,10 @@ ASTNode const* LanguageServer::requestASTNode(std::string const& _sourceUnitName
 	if (!m_fileRepository.sourceUnits().count(_sourceUnitName))
 		return nullptr;
 
-	optional<int> sourcePos = m_compilerStack.charStream(_sourceUnitName)
-		.translateLineColumnToPosition(_filePos);
-	if (!sourcePos.has_value())
+	if (optional<int> sourcePos =
+		m_compilerStack.charStream(_sourceUnitName).translateLineColumnToPosition(_filePos))
+		return locateInnermostASTNode(*sourcePos, m_compilerStack.ast(_sourceUnitName));
+	else
 		return nullptr;
-
-	return locateInnermostASTNode(*sourcePos, m_compilerStack.ast(_sourceUnitName));
 }
 

libsolidity/lsp/LanguageServer.h

@@ -59,7 +59,7 @@ public:
 
 	FileRepository& fileRepository() noexcept { return m_fileRepository; }
 	Transport& client() noexcept { return m_client; }
-	frontend::ASTNode const* requestASTNode(std::string const& _sourceUnitName, langutil::LineColumn const& _filePos);
+	frontend::ASTNode const* astNodeAtSourceLocation(std::string const& _sourceUnitName, langutil::LineColumn const& _filePos);
 	langutil::CharStreamProvider const& charStreamProvider() const noexcept { return m_compilerStack; }
 
 private:
@@ -71,6 +71,7 @@ private:
 	void handleTextDocumentDidOpen(Json::Value const& _args);
 	void handleTextDocumentDidChange(Json::Value const& _args);
 	void handleTextDocumentDidClose(Json::Value const& _args);
+	void handleGotoDefinition(MessageID _id, Json::Value const& _args);
 
 	/// Invoked when the server user-supplied configuration changes (initiated by the client).
 	void changeConfiguration(Json::Value const&);
@@ -79,12 +80,6 @@ private:
 	void compile();
 	using MessageHandler = std::function<void(MessageID, Json::Value const&)>;
 
-	/// @returns the source location given a source unit name and an LSP Range object,
-	/// or nullopt on failure.
-	std::optional<langutil::SourceLocation> parseRange(
-		std::string const& _sourceUnitName,
-		Json::Value const& _range
-	);
 	Json::Value toRange(langutil::SourceLocation const& _location);
 	Json::Value toJson(langutil::SourceLocation const& _location);
 

libsolidity/lsp/Utils.cpp

@@ -1,9 +1,30 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+
 #include <liblangutil/CharStreamProvider.h>
 #include <liblangutil/Exceptions.h>
 #include <libsolidity/ast/AST.h>
 #include <libsolidity/lsp/FileRepository.h>
 #include <libsolidity/lsp/Utils.h>
 
+#include <fmt/format.h>
+#include <fstream>
+
 namespace solidity::lsp
 {
 
@@ -19,7 +40,7 @@ optional<LineColumn> parseLineColumn(Json::Value const& _lineColumn)
 		return nullopt;
 }
 
-Json::Value toJson(LineColumn _pos)
+Json::Value toJson(LineColumn const& _pos)
 {
 	Json::Value json = Json::objectValue;
 	json["line"] = max(_pos.line, 0);
@@ -36,24 +57,20 @@ Json::Value toJsonRange(LineColumn const& _start, LineColumn const& _end)
 	return json;
 }
 
-vector<Declaration const*> allAnnotatedDeclarations(Expression const* _expression)
+Declaration const* referencedDeclaration(Expression const* _expression)
 {
-	vector<Declaration const*> output;
-
 	if (auto const* identifier = dynamic_cast<Identifier const*>(_expression))
-	{
-		output.push_back(identifier->annotation().referencedDeclaration);
-		output += identifier->annotation().candidateDeclarations;
-	}
-	else if (auto const* memberAccess = dynamic_cast<MemberAccess const*>(_expression))
-	{
-		output.push_back(memberAccess->annotation().referencedDeclaration);
-	}
+		if (Declaration const* referencedDeclaration = identifier->annotation().referencedDeclaration)
+			return referencedDeclaration;
 
-	return output;
+	if (auto const* memberAccess = dynamic_cast<MemberAccess const*>(_expression))
+		if (memberAccess->annotation().referencedDeclaration)
+			return memberAccess->annotation().referencedDeclaration;
+
+	return nullptr;
 }
 
-optional<SourceLocation> declarationPosition(Declaration const* _declaration)
+optional<SourceLocation> declarationLocation(Declaration const* _declaration)
 {
 	if (!_declaration)
 		return nullopt;
@@ -67,4 +84,35 @@ optional<SourceLocation> declarationPosition(Declaration const* _declaration)
 	return nullopt;
 }
 
+optional<SourceLocation> parsePosition(
+	FileRepository const& _fileRepository,
+	string const& _sourceUnitName,
+	Json::Value const& _position
+)
+{
+	if (!_fileRepository.sourceUnits().count(_sourceUnitName))
+		return nullopt;
+
+	if (optional<LineColumn> lineColumn = parseLineColumn(_position))
+		if (optional<int> const offset = CharStream::translateLineColumnToPosition(
+			_fileRepository.sourceUnits().at(_sourceUnitName),
+			*lineColumn
+		))
+			return SourceLocation{*offset, *offset, make_shared<string>(_sourceUnitName)};
+	return nullopt;
+}
+
+optional<SourceLocation> parseRange(FileRepository const& _fileRepository, string const& _sourceUnitName, Json::Value const& _range)
+{
+	if (!_range.isObject())
+		return nullopt;
+	optional<SourceLocation> start = parsePosition(_fileRepository, _sourceUnitName, _range["start"]);
+	optional<SourceLocation> end = parsePosition(_fileRepository, _sourceUnitName, _range["end"]);
+	if (!start || !end)
+		return nullopt;
+	solAssert(*start->sourceName == *end->sourceName);
+	start->end = end->end;
+	return start;
+}
+
 }

libsolidity/lsp/Utils.h

@@ -1,3 +1,21 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+
 #pragma once
 
 #include <liblangutil/SourceLocation.h>
@@ -9,6 +27,13 @@
 #include <optional>
 #include <vector>
 
+#if !defined(NDEBUG)
+#include <fstream>
+#define lspDebug(message) (std::ofstream("/tmp/solc.log", std::ios::app) << (message) << std::endl)
+#else
+#define lspDebug(message) do {} while (0)
+#endif
+
 namespace solidity::langutil
 {
 class CharStreamProvider;
@@ -20,10 +45,35 @@ namespace solidity::lsp
 class FileRepository;
 
 std::optional<langutil::LineColumn> parseLineColumn(Json::Value const& _lineColumn);
-Json::Value toJson(langutil::LineColumn _pos);
+Json::Value toJson(langutil::LineColumn const& _pos);
 Json::Value toJsonRange(langutil::LineColumn const& _start, langutil::LineColumn const& _end);
 
-std::vector<frontend::Declaration const*> allAnnotatedDeclarations(frontend::Expression const* _expression);
-std::optional<langutil::SourceLocation> declarationPosition(frontend::Declaration const* _declaration);
+/// @returns the source location given a source unit name and an LSP Range object,
+/// or nullopt on failure.
+std::optional<langutil::SourceLocation> parsePosition(
+	FileRepository const& _fileRepository,
+	std::string const& _sourceUnitName,
+	Json::Value const& _position
+);
+
+/// @returns the source location given a source unit name and an LSP Range object,
+/// or nullopt on failure.
+std::optional<langutil::SourceLocation> parseRange(
+	FileRepository const& _fileRepository,
+	std::string const& _sourceUnitName,
+	Json::Value const& _range
+);
+
+/// Extracts the resolved declaration of the given expression AST node.
+///
+/// This may for example be the type declaration of an identifier,
+/// or the type declaration of a structured member identifier.
+///
+/// @returns the resolved type declaration if found, or nullptr otherwise.
+frontend::Declaration const* referencedDeclaration(frontend::Expression const* _expression);
+
+/// @returns the location of the declaration's name, if present, or the location of the complete
+/// declaration otherwise. If the input declaration is nullptr, std::nullopt is returned instead.
+std::optional<langutil::SourceLocation> declarationLocation(frontend::Declaration const* _declaration);
 
 }