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| //===--- IsolateDeclarationCheck.cpp - clang-tidy -------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "IsolateDeclarationCheck.h"
#include "../utils/LexerUtils.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
using namespace clang::tidy::utils::lexer;
namespace clang {
namespace tidy {
namespace readability {
namespace {
AST_MATCHER(DeclStmt, isSingleDecl) { return Node.isSingleDecl(); }
AST_MATCHER(DeclStmt, onlyDeclaresVariables) {
return llvm::all_of(Node.decls(), [](Decl *D) { return isa<VarDecl>(D); });
}
} // namespace
void IsolateDeclarationCheck::registerMatchers(MatchFinder *Finder) {
Finder->addMatcher(declStmt(onlyDeclaresVariables(), unless(isSingleDecl()),
hasParent(compoundStmt()))
.bind("decl_stmt"),
this);
}
static SourceLocation findStartOfIndirection(SourceLocation Start,
int Indirections,
const SourceManager &SM,
const LangOptions &LangOpts) {
assert(Indirections >= 0 && "Indirections must be non-negative");
if (Indirections == 0)
return Start;
// Note that the post-fix decrement is necessary to perform the correct
// number of transformations.
while (Indirections-- != 0) {
Start = findPreviousAnyTokenKind(Start, SM, LangOpts, tok::star, tok::amp);
if (Start.isInvalid() || Start.isMacroID())
return SourceLocation();
}
return Start;
}
static bool isMacroID(SourceRange R) {
return R.getBegin().isMacroID() || R.getEnd().isMacroID();
}
/// This function counts the number of written indirections for the given
/// Type \p T. It does \b NOT resolve typedefs as it's a helper for lexing
/// the source code.
/// \see declRanges
static int countIndirections(const Type *T, int Indirections = 0) {
if (T->isFunctionPointerType()) {
const auto *Pointee = T->getPointeeType()->castAs<FunctionType>();
return countIndirections(
Pointee->getReturnType().IgnoreParens().getTypePtr(), ++Indirections);
}
// Note: Do not increment the 'Indirections' because it is not yet clear
// if there is an indirection added in the source code of the array
// declaration.
if (const auto *AT = dyn_cast<ArrayType>(T))
return countIndirections(AT->getElementType().IgnoreParens().getTypePtr(),
Indirections);
if (isa<PointerType>(T) || isa<ReferenceType>(T))
return countIndirections(T->getPointeeType().IgnoreParens().getTypePtr(),
++Indirections);
return Indirections;
}
static bool typeIsMemberPointer(const Type *T) {
if (isa<ArrayType>(T))
return typeIsMemberPointer(T->getArrayElementTypeNoTypeQual());
if ((isa<PointerType>(T) || isa<ReferenceType>(T)) &&
isa<PointerType>(T->getPointeeType()))
return typeIsMemberPointer(T->getPointeeType().getTypePtr());
return isa<MemberPointerType>(T);
}
/// This function tries to extract the SourceRanges that make up all
/// declarations in this \c DeclStmt.
///
/// The resulting vector has the structure {UnderlyingType, Decl1, Decl2, ...}.
/// Each \c SourceRange is of the form [Begin, End).
/// If any of the create ranges is invalid or in a macro the result will be
/// \c None.
/// If the \c DeclStmt contains only one declaration, the result is \c None.
/// If the \c DeclStmt contains declarations other than \c VarDecl the result
/// is \c None.
///
/// \code
/// int * ptr1 = nullptr, value = 42;
/// // [ ][ ] [ ] - The ranges here are inclusive
/// \endcode
/// \todo Generalize this function to take other declarations than \c VarDecl.
static Optional<std::vector<SourceRange>>
declRanges(const DeclStmt *DS, const SourceManager &SM,
const LangOptions &LangOpts) {
std::size_t DeclCount = std::distance(DS->decl_begin(), DS->decl_end());
if (DeclCount < 2)
return None;
if (rangeContainsExpansionsOrDirectives(DS->getSourceRange(), SM, LangOpts))
return None;
// The initial type of the declaration and each declaration has it's own
// slice. This is necessary, because pointers and references bind only
// to the local variable and not to all variables in the declaration.
// Example: 'int *pointer, value = 42;'
std::vector<SourceRange> Slices;
Slices.reserve(DeclCount + 1);
// Calculate the first slice, for now only variables are handled but in the
// future this should be relaxed and support various kinds of declarations.
const auto *FirstDecl = dyn_cast<VarDecl>(*DS->decl_begin());
if (FirstDecl == nullptr)
return None;
// FIXME: Member pointers are not transformed correctly right now, that's
// why they are treated as problematic here.
if (typeIsMemberPointer(FirstDecl->getType().IgnoreParens().getTypePtr()))
return None;
// Consider the following case: 'int * pointer, value = 42;'
// Created slices (inclusive) [ ][ ] [ ]
// Because 'getBeginLoc' points to the start of the variable *name*, the
// location of the pointer must be determined separatly.
SourceLocation Start = findStartOfIndirection(
FirstDecl->getLocation(),
countIndirections(FirstDecl->getType().IgnoreParens().getTypePtr()), SM,
LangOpts);
// Fix function-pointer declarations that have a '(' in front of the
// pointer.
// Example: 'void (*f2)(int), (*g2)(int, float) = gg;'
// Slices: [ ][ ] [ ]
if (FirstDecl->getType()->isFunctionPointerType())
Start = findPreviousTokenKind(Start, SM, LangOpts, tok::l_paren);
// It is popssible that a declarator is wrapped with parens.
// Example: 'float (((*f_ptr2)))[42], *f_ptr3, ((f_value2)) = 42.f;'
// The slice for the type-part must not contain these parens. Consequently
// 'Start' is moved to the most left paren if there are parens.
while (true) {
if (Start.isInvalid() || Start.isMacroID())
break;
Token T = getPreviousToken(Start, SM, LangOpts);
if (T.is(tok::l_paren)) {
Start = findPreviousTokenStart(Start, SM, LangOpts);
continue;
}
break;
}
SourceRange DeclRange(DS->getBeginLoc(), Start);
if (DeclRange.isInvalid() || isMacroID(DeclRange))
return None;
// The first slice, that is prepended to every isolated declaration, is
// created.
Slices.emplace_back(DeclRange);
// Create all following slices that each declare a variable.
SourceLocation DeclBegin = Start;
for (const auto &Decl : DS->decls()) {
const auto *CurrentDecl = cast<VarDecl>(Decl);
// FIXME: Member pointers are not transformed correctly right now, that's
// why they are treated as problematic here.
if (typeIsMemberPointer(CurrentDecl->getType().IgnoreParens().getTypePtr()))
return None;
SourceLocation DeclEnd =
CurrentDecl->hasInit()
? findNextTerminator(CurrentDecl->getInit()->getEndLoc(), SM,
LangOpts)
: findNextTerminator(CurrentDecl->getEndLoc(), SM, LangOpts);
SourceRange VarNameRange(DeclBegin, DeclEnd);
if (VarNameRange.isInvalid() || isMacroID(VarNameRange))
return None;
Slices.emplace_back(VarNameRange);
DeclBegin = DeclEnd.getLocWithOffset(1);
}
return Slices;
}
static Optional<std::vector<StringRef>>
collectSourceRanges(llvm::ArrayRef<SourceRange> Ranges, const SourceManager &SM,
const LangOptions &LangOpts) {
std::vector<StringRef> Snippets;
Snippets.reserve(Ranges.size());
for (const auto &Range : Ranges) {
CharSourceRange CharRange = Lexer::getAsCharRange(
CharSourceRange::getCharRange(Range.getBegin(), Range.getEnd()), SM,
LangOpts);
if (CharRange.isInvalid())
return None;
bool InvalidText = false;
StringRef Snippet =
Lexer::getSourceText(CharRange, SM, LangOpts, &InvalidText);
if (InvalidText)
return None;
Snippets.emplace_back(Snippet);
}
return Snippets;
}
/// Expects a vector {TypeSnippet, Firstdecl, SecondDecl, ...}.
static std::vector<std::string>
createIsolatedDecls(llvm::ArrayRef<StringRef> Snippets) {
// The first section is the type snippet, which does not make a decl itself.
assert(Snippets.size() > 2 && "Not enough snippets to create isolated decls");
std::vector<std::string> Decls(Snippets.size() - 1);
for (std::size_t I = 1; I < Snippets.size(); ++I)
Decls[I - 1] = Twine(Snippets[0])
.concat(Snippets[0].endswith(" ") ? "" : " ")
.concat(Snippets[I].ltrim())
.concat(";")
.str();
return Decls;
}
void IsolateDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
const auto *WholeDecl = Result.Nodes.getNodeAs<DeclStmt>("decl_stmt");
auto Diag =
diag(WholeDecl->getBeginLoc(),
"multiple declarations in a single statement reduces readability");
Optional<std::vector<SourceRange>> PotentialRanges =
declRanges(WholeDecl, *Result.SourceManager, getLangOpts());
if (!PotentialRanges)
return;
Optional<std::vector<StringRef>> PotentialSnippets = collectSourceRanges(
*PotentialRanges, *Result.SourceManager, getLangOpts());
if (!PotentialSnippets)
return;
std::vector<std::string> NewDecls = createIsolatedDecls(*PotentialSnippets);
std::string Replacement = llvm::join(
NewDecls,
(Twine("\n") + Lexer::getIndentationForLine(WholeDecl->getBeginLoc(),
*Result.SourceManager))
.str());
Diag << FixItHint::CreateReplacement(WholeDecl->getSourceRange(),
Replacement);
}
} // namespace readability
} // namespace tidy
} // namespace clang
|