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//===--- TimeSubtractionCheck.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 "TimeSubtractionCheck.h"
#include "DurationRewriter.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
#include "clang/Tooling/FixIt.h"
#include <optional>
using namespace clang::ast_matchers;
namespace clang::tidy::abseil {
// Returns `true` if `Range` is inside a macro definition.
static bool insideMacroDefinition(const MatchFinder::MatchResult &Result,
SourceRange Range) {
return !clang::Lexer::makeFileCharRange(
clang::CharSourceRange::getCharRange(Range),
*Result.SourceManager, Result.Context->getLangOpts())
.isValid();
}
static bool isConstructorAssignment(const MatchFinder::MatchResult &Result,
const Expr *Node) {
// For C++14 and earlier there are elidable constructors that must be matched
// in hasParent. The elidable constructors do not exist in C++17 and later and
// therefore an additional check that does not match against the elidable
// constructors are needed for this case.
return selectFirst<const Expr>(
"e",
match(expr(anyOf(
callExpr(hasParent(materializeTemporaryExpr(hasParent(
cxxConstructExpr(hasParent(exprWithCleanups(
hasParent(varDecl()))))))))
.bind("e"),
callExpr(hasParent(varDecl())).bind("e"))),
*Node, *Result.Context)) != nullptr;
}
static bool isArgument(const MatchFinder::MatchResult &Result,
const Expr *Node) {
// For the same reason as in isConstructorAssignment two AST shapes need to be
// matched here.
return selectFirst<const Expr>(
"e",
match(
expr(anyOf(
expr(hasParent(materializeTemporaryExpr(
hasParent(cxxConstructExpr(
hasParent(callExpr()),
unless(hasParent(cxxOperatorCallExpr())))))))
.bind("e"),
expr(hasParent(callExpr()),
unless(hasParent(cxxOperatorCallExpr())))
.bind("e"))),
*Node, *Result.Context)) != nullptr;
}
static bool isReturn(const MatchFinder::MatchResult &Result, const Expr *Node) {
// For the same reason as in isConstructorAssignment two AST shapes need to be
// matched here.
return selectFirst<const Expr>(
"e",
match(expr(anyOf(
expr(hasParent(materializeTemporaryExpr(hasParent(
cxxConstructExpr(hasParent(exprWithCleanups(
hasParent(returnStmt()))))))))
.bind("e"),
expr(hasParent(returnStmt())).bind("e"))),
*Node, *Result.Context)) != nullptr;
}
static bool parensRequired(const MatchFinder::MatchResult &Result,
const Expr *Node) {
// TODO: Figure out any more contexts in which we can omit the surrounding
// parentheses.
return !(isConstructorAssignment(Result, Node) || isArgument(Result, Node) ||
isReturn(Result, Node));
}
void TimeSubtractionCheck::emitDiagnostic(const Expr *Node,
llvm::StringRef Replacement) {
diag(Node->getBeginLoc(), "perform subtraction in the time domain")
<< FixItHint::CreateReplacement(Node->getSourceRange(), Replacement);
}
void TimeSubtractionCheck::registerMatchers(MatchFinder *Finder) {
for (const char *ScaleName :
{"Hours", "Minutes", "Seconds", "Millis", "Micros", "Nanos"}) {
std::string TimeInverse = (llvm::Twine("ToUnix") + ScaleName).str();
std::optional<DurationScale> Scale = getScaleForTimeInverse(TimeInverse);
assert(Scale && "Unknown scale encountered");
auto TimeInverseMatcher = callExpr(callee(
functionDecl(hasName((llvm::Twine("::absl::") + TimeInverse).str()))
.bind("func_decl")));
// Match the cases where we know that the result is a 'Duration' and the
// first argument is a 'Time'. Just knowing the type of the first operand
// is not sufficient, since the second operand could be either a 'Time' or
// a 'Duration'. If we know the result is a 'Duration', we can then infer
// that the second operand must be a 'Time'.
auto CallMatcher =
callExpr(
callee(functionDecl(hasName(getDurationFactoryForScale(*Scale)))),
hasArgument(0, binaryOperator(hasOperatorName("-"),
hasLHS(TimeInverseMatcher))
.bind("binop")))
.bind("outer_call");
Finder->addMatcher(CallMatcher, this);
// Match cases where we know the second operand is a 'Time'. Since
// subtracting a 'Time' from a 'Duration' is not defined, in these cases,
// we always know the first operand is a 'Time' if the second is a 'Time'.
auto OperandMatcher =
binaryOperator(hasOperatorName("-"), hasRHS(TimeInverseMatcher))
.bind("binop");
Finder->addMatcher(OperandMatcher, this);
}
}
void TimeSubtractionCheck::check(const MatchFinder::MatchResult &Result) {
const auto *BinOp = Result.Nodes.getNodeAs<BinaryOperator>("binop");
std::string InverseName =
Result.Nodes.getNodeAs<FunctionDecl>("func_decl")->getNameAsString();
if (insideMacroDefinition(Result, BinOp->getSourceRange()))
return;
std::optional<DurationScale> Scale = getScaleForTimeInverse(InverseName);
if (!Scale)
return;
const auto *OuterCall = Result.Nodes.getNodeAs<CallExpr>("outer_call");
if (OuterCall) {
if (insideMacroDefinition(Result, OuterCall->getSourceRange()))
return;
// We're working with the first case of matcher, and need to replace the
// entire 'Duration' factory call. (Which also means being careful about
// our order-of-operations and optionally putting in some parenthesis.
bool NeedParens = parensRequired(Result, OuterCall);
emitDiagnostic(
OuterCall,
(llvm::Twine(NeedParens ? "(" : "") +
rewriteExprFromNumberToTime(Result, *Scale, BinOp->getLHS()) + " - " +
rewriteExprFromNumberToTime(Result, *Scale, BinOp->getRHS()) +
(NeedParens ? ")" : ""))
.str());
} else {
// We're working with the second case of matcher, and either just need to
// change the arguments, or perhaps remove an outer function call. In the
// latter case (addressed first), we also need to worry about parenthesis.
const auto *MaybeCallArg = selectFirst<const CallExpr>(
"arg", match(expr(hasAncestor(
callExpr(callee(functionDecl(hasName(
getDurationFactoryForScale(*Scale)))))
.bind("arg"))),
*BinOp, *Result.Context));
if (MaybeCallArg && MaybeCallArg->getArg(0)->IgnoreImpCasts() == BinOp &&
!insideMacroDefinition(Result, MaybeCallArg->getSourceRange())) {
// Handle the case where the matched expression is inside a call which
// converts it from the inverse to a Duration. In this case, we replace
// the outer with just the subtraction expression, which gives the right
// type and scale, taking care again about parenthesis.
bool NeedParens = parensRequired(Result, MaybeCallArg);
emitDiagnostic(
MaybeCallArg,
(llvm::Twine(NeedParens ? "(" : "") +
rewriteExprFromNumberToTime(Result, *Scale, BinOp->getLHS()) +
" - " +
rewriteExprFromNumberToTime(Result, *Scale, BinOp->getRHS()) +
(NeedParens ? ")" : ""))
.str());
} else {
// In the last case, just convert the arguments and wrap the result in
// the correct inverse function.
emitDiagnostic(
BinOp,
(llvm::Twine(
getDurationInverseForScale(*Scale).second.str().substr(2)) +
"(" + rewriteExprFromNumberToTime(Result, *Scale, BinOp->getLHS()) +
" - " +
rewriteExprFromNumberToTime(Result, *Scale, BinOp->getRHS()) + ")")
.str());
}
}
}
} // namespace clang::tidy::abseil
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