Adding upstream version 1:7.0.4.upstream/1%7.0.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 668 insertions, 0 deletions

diff --git a/compilerplugins/clang/unnecessaryparen.cxx b/compilerplugins/clang/unnecessaryparen.cxx
new file mode 100644
index 000000000..e93dfa64b
--- /dev/null
+++ b/compilerplugins/clang/unnecessaryparen.cxx
@@ -0,0 +1,668 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef LO_CLANG_SHARED_PLUGINS
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+#include <unordered_set>
+
+#include <clang/AST/CXXInheritance.h>
+
+#include "config_clang.h"
+
+#include "compat.hxx"
+#include "plugin.hxx"
+
+/**
+look for unnecessary parentheses
+*/
+
+namespace {
+
+// Like clang::Stmt::IgnoreImplicit (lib/AST/Stmt.cpp), but also ignoring CXXConstructExpr and
+// looking through implicit UserDefinedConversion's member function call:
+Expr const * ignoreAllImplicit(Expr const * expr) {
+    while (true)
+    {
+        auto oldExpr = expr;
+        if (auto const e = dyn_cast<ExprWithCleanups>(expr)) {
+            expr = e->getSubExpr();
+        }
+        else if (auto const e = dyn_cast<CXXConstructExpr>(expr)) {
+            if (e->getNumArgs() == 1) {
+                expr = e->getArg(0);
+            }
+        }
+        else if (auto const e = dyn_cast<MaterializeTemporaryExpr>(expr)) {
+            expr = compat::getSubExpr(e);
+        }
+        else if (auto const e = dyn_cast<CXXBindTemporaryExpr>(expr)) {
+            expr = e->getSubExpr();
+        }
+        else if (auto const e = dyn_cast<ImplicitCastExpr>(expr)) {
+            expr = e->getSubExpr();
+            if (e->getCastKind() == CK_UserDefinedConversion) {
+                auto const ce = cast<CXXMemberCallExpr>(expr);
+                assert(ce->getNumArgs() == 0);
+                expr = ce->getImplicitObjectArgument();
+            }
+        }
+#if CLANG_VERSION >= 80000
+        else if (auto const e = dyn_cast<ConstantExpr>(expr)) {
+            expr = e->getSubExpr();
+        }
+#endif
+        if (expr == oldExpr)
+            return expr;
+    }
+    return expr;
+}
+
+class UnnecessaryParen:
+    public loplugin::FilteringRewritePlugin<UnnecessaryParen>
+{
+public:
+    explicit UnnecessaryParen(loplugin::InstantiationData const & data):
+        FilteringRewritePlugin(data) {}
+
+    virtual bool preRun() override
+    {
+        StringRef fn(handler.getMainFileName());
+        // fixing this, makes the source in the .y files look horrible
+        if (loplugin::isSamePathname(fn, WORKDIR "/YaccTarget/unoidl/source/sourceprovider-parser.cxx"))
+            return false;
+        if (loplugin::isSamePathname(fn, WORKDIR "/YaccTarget/idlc/source/parser.cxx"))
+            return false;
+        return true;
+    }
+    virtual void run() override
+    {
+        if( preRun())
+            TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitParenExpr(const ParenExpr *);
+    bool VisitIfStmt(const IfStmt *);
+    bool VisitDoStmt(const DoStmt *);
+    bool VisitWhileStmt(const WhileStmt *);
+    bool VisitForStmt(ForStmt const * stmt);
+    bool VisitSwitchStmt(const SwitchStmt *);
+    bool VisitCaseStmt(const CaseStmt *);
+    bool VisitReturnStmt(const ReturnStmt* );
+    bool VisitCallExpr(const CallExpr *);
+    bool VisitVarDecl(const VarDecl *);
+    bool VisitCXXOperatorCallExpr(const CXXOperatorCallExpr *);
+    bool VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr const *);
+    bool VisitConditionalOperator(ConditionalOperator const * expr);
+    bool VisitBinaryConditionalOperator(BinaryConditionalOperator const * expr);
+    bool VisitMemberExpr(const MemberExpr *f);
+    bool VisitCXXDeleteExpr(const CXXDeleteExpr *);
+
+    bool VisitImplicitCastExpr(ImplicitCastExpr const * expr) {
+        if (ignoreLocation(expr)) {
+            return true;
+        }
+        if (expr->getCastKind() != CK_UserDefinedConversion) {
+            return true;
+        }
+        // Filter out a MemberExpr (resp. a ParenExpr sub-expr, if any, as would be found by
+        // VisitMemberExpr) that is part of a CXXMemberCallExpr which in turn is part of an
+        // ImplicitCastExpr, so that VisitMemberExpr doesn't erroneously pick it up (and note that
+        // CXXMemberCallExpr's getImplicitObjectArgument() skips past the underlying MemberExpr):
+        if (auto const e1 = dyn_cast<CXXMemberCallExpr>(expr->getSubExpr())) {
+            if (auto const e2 = dyn_cast<ParenExpr>(
+                    e1->getImplicitObjectArgument()->IgnoreImpCasts()))
+            {
+                handled_.insert(e2);
+            }
+        }
+        return true;
+    }
+
+private:
+    void VisitSomeStmt(Stmt const * stmt, const Expr* cond, StringRef stmtName);
+
+    void handleUnreachableCodeConditionParens(Expr const * expr);
+
+    // Hack for libxml2's BAD_CAST object-like macro (expanding to "(xmlChar *)"), which is
+    // typically used as if it were a function-like macro, e.g., as "BAD_CAST(pName)" in
+    // SwNode::dumpAsXml (sw/source/core/docnode/node.cxx):
+    bool isPrecededBy_BAD_CAST(Expr const * expr);
+
+    bool badCombination(SourceLocation loc, int prevOffset, int nextOffset);
+
+    bool removeParens(ParenExpr const * expr);
+
+    std::unordered_set<ParenExpr const *> handled_;
+};
+
+bool UnnecessaryParen::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr const * expr)
+{
+    if (expr->getKind() == UETT_SizeOf && !expr->isArgumentType()) {
+        if (auto const e = dyn_cast<ParenExpr>(ignoreAllImplicit(expr->getArgumentExpr()))) {
+            handled_.insert(e);
+        }
+    }
+    return true;
+}
+
+bool UnnecessaryParen::VisitConditionalOperator(ConditionalOperator const * expr) {
+    handleUnreachableCodeConditionParens(expr->getCond());
+    return true;
+}
+
+bool UnnecessaryParen::VisitBinaryConditionalOperator(BinaryConditionalOperator const * expr) {
+    handleUnreachableCodeConditionParens(expr->getCond());
+    return true;
+}
+
+bool UnnecessaryParen::VisitParenExpr(const ParenExpr* parenExpr)
+{
+    if (ignoreLocation(parenExpr))
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+    if (handled_.find(parenExpr) != handled_.end())
+        return true;
+
+    auto subExpr = ignoreAllImplicit(parenExpr->getSubExpr());
+
+    if (auto subParenExpr = dyn_cast<ParenExpr>(subExpr))
+    {
+        if (compat::getBeginLoc(subParenExpr).isMacroID())
+            return true;
+        report(
+            DiagnosticsEngine::Warning, "parentheses around parentheses",
+            compat::getBeginLoc(parenExpr))
+            << parenExpr->getSourceRange();
+        handled_.insert(subParenExpr);
+    }
+
+    // Somewhat redundantly add parenExpr to handled_, so that issues within InitListExpr don't get
+    // reported twice (without having to change TraverseInitListExpr to only either traverse the
+    // syntactic or semantic form, as other plugins do):
+
+    if (isa<DeclRefExpr>(subExpr)) {
+        if (!isPrecededBy_BAD_CAST(parenExpr)) {
+            report(
+                DiagnosticsEngine::Warning, "unnecessary parentheses around identifier",
+                compat::getBeginLoc(parenExpr))
+                << parenExpr->getSourceRange();
+            handled_.insert(parenExpr);
+        }
+    } else if (isa<IntegerLiteral>(subExpr) || isa<CharacterLiteral>(subExpr)
+               || isa<FloatingLiteral>(subExpr) || isa<ImaginaryLiteral>(subExpr)
+               || isa<CXXBoolLiteralExpr>(subExpr) || isa<CXXNullPtrLiteralExpr>(subExpr)
+               || isa<ObjCBoolLiteralExpr>(subExpr))
+    {
+        auto const loc = compat::getBeginLoc(subExpr);
+        if (loc.isMacroID() && compiler.getSourceManager().isAtStartOfImmediateMacroExpansion(loc))
+        {
+            // just in case the macro could also expand to something that /would/ require
+            // parentheses here
+            return true;
+        }
+        report(
+            DiagnosticsEngine::Warning, "unnecessary parentheses around literal",
+            compat::getBeginLoc(parenExpr))
+            << parenExpr->getSourceRange();
+        handled_.insert(parenExpr);
+    } else if (auto const e = dyn_cast<clang::StringLiteral>(subExpr)) {
+        if (e->getNumConcatenated() == 1 && !isPrecededBy_BAD_CAST(parenExpr)) {
+            report(
+                DiagnosticsEngine::Warning,
+                "unnecessary parentheses around single-token string literal",
+                compat::getBeginLoc(parenExpr))
+                << parenExpr->getSourceRange();
+            handled_.insert(parenExpr);
+        }
+    } else if (auto const e = dyn_cast<UnaryOperator>(subExpr)) {
+        auto const op = e->getOpcode();
+        if (op == UO_Plus || op == UO_Minus) {
+            auto const e2 = e->getSubExpr();
+            if (isa<IntegerLiteral>(e2) || isa<FloatingLiteral>(e2) || isa<ImaginaryLiteral>(e2)) {
+                report(
+                    DiagnosticsEngine::Warning,
+                    "unnecessary parentheses around signed numeric literal",
+                    compat::getBeginLoc(parenExpr))
+                    << parenExpr->getSourceRange();
+                handled_.insert(parenExpr);
+            }
+        }
+    } else if (isa<CXXNamedCastExpr>(subExpr)) {
+        if (!removeParens(parenExpr)) {
+            report(
+                DiagnosticsEngine::Warning, "unnecessary parentheses around cast",
+                compat::getBeginLoc(parenExpr))
+                << parenExpr->getSourceRange();
+        }
+        handled_.insert(parenExpr);
+    } else if (auto memberExpr = dyn_cast<MemberExpr>(subExpr)) {
+        if (isa<CXXThisExpr>(ignoreAllImplicit(memberExpr->getBase()))) {
+            report(
+                DiagnosticsEngine::Warning, "unnecessary parentheses around member expr",
+                compat::getBeginLoc(parenExpr))
+                << parenExpr->getSourceRange();
+            handled_.insert(parenExpr);
+        }
+    }
+
+    return true;
+}
+
+bool UnnecessaryParen::VisitIfStmt(const IfStmt* ifStmt)
+{
+    handleUnreachableCodeConditionParens(ifStmt->getCond());
+    VisitSomeStmt(ifStmt, ifStmt->getCond(), "if");
+    return true;
+}
+
+bool UnnecessaryParen::VisitDoStmt(const DoStmt* doStmt)
+{
+    VisitSomeStmt(doStmt, doStmt->getCond(), "do");
+    return true;
+}
+
+bool UnnecessaryParen::VisitWhileStmt(const WhileStmt* whileStmt)
+{
+    handleUnreachableCodeConditionParens(whileStmt->getCond());
+    VisitSomeStmt(whileStmt, whileStmt->getCond(), "while");
+    return true;
+}
+
+bool UnnecessaryParen::VisitForStmt(ForStmt const * stmt) {
+    if (auto const cond = stmt->getCond()) {
+        handleUnreachableCodeConditionParens(cond);
+    }
+    return true;
+}
+
+bool UnnecessaryParen::VisitSwitchStmt(const SwitchStmt* switchStmt)
+{
+    VisitSomeStmt(switchStmt, switchStmt->getCond(), "switch");
+    return true;
+}
+
+bool UnnecessaryParen::VisitCaseStmt(const CaseStmt* caseStmt)
+{
+    VisitSomeStmt(caseStmt, caseStmt->getLHS(), "case");
+    return true;
+}
+
+bool UnnecessaryParen::VisitReturnStmt(const ReturnStmt* returnStmt)
+{
+    if (ignoreLocation(returnStmt))
+        return true;
+
+    if (!returnStmt->getRetValue())
+        return true;
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(returnStmt->getRetValue()));
+    if (!parenExpr)
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+    // assignments need extra parentheses or they generate a compiler warning
+    auto binaryOp = dyn_cast<BinaryOperator>(parenExpr->getSubExpr());
+    if (binaryOp && binaryOp->getOpcode() == BO_Assign)
+        return true;
+
+    // only non-operator-calls for now
+    auto subExpr = ignoreAllImplicit(parenExpr->getSubExpr());
+    if (isa<CallExpr>(subExpr) && !isa<CXXOperatorCallExpr>(subExpr))
+    {
+        report(
+            DiagnosticsEngine::Warning, "parentheses immediately inside return statement",
+            compat::getBeginLoc(parenExpr))
+            << parenExpr->getSourceRange();
+        handled_.insert(parenExpr);
+    }
+    return true;
+}
+
+void UnnecessaryParen::VisitSomeStmt(const Stmt * stmt, const Expr* cond, StringRef stmtName)
+{
+    if (ignoreLocation(stmt))
+        return;
+
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(cond));
+    if (parenExpr) {
+        if (handled_.find(parenExpr) != handled_.end()) {
+            return;
+        }
+        if (compat::getBeginLoc(parenExpr).isMacroID())
+            return;
+        // assignments need extra parentheses or they generate a compiler warning
+        auto binaryOp = dyn_cast<BinaryOperator>(parenExpr->getSubExpr());
+        if (binaryOp && binaryOp->getOpcode() == BO_Assign)
+            return;
+        if (auto const opCall = dyn_cast<CXXOperatorCallExpr>(parenExpr->getSubExpr())) {
+            if (opCall->getOperator() == OO_Equal) {
+                return;
+            }
+        }
+        report(
+            DiagnosticsEngine::Warning, "parentheses immediately inside %0 statement",
+            compat::getBeginLoc(parenExpr))
+            << stmtName
+            << parenExpr->getSourceRange();
+        handled_.insert(parenExpr);
+    }
+}
+
+bool UnnecessaryParen::VisitCallExpr(const CallExpr* callExpr)
+{
+    if (ignoreLocation(callExpr))
+        return true;
+    if (callExpr->getNumArgs() != 1 || isa<CXXOperatorCallExpr>(callExpr))
+        return true;
+
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(callExpr->getArg(0)));
+    if (!parenExpr)
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+    // assignments need extra parentheses or they generate a compiler warning
+    auto binaryOp = dyn_cast<BinaryOperator>(parenExpr->getSubExpr());
+    if (binaryOp && binaryOp->getOpcode() == BO_Assign)
+        return true;
+    report(
+        DiagnosticsEngine::Warning, "parentheses immediately inside single-arg call",
+        compat::getBeginLoc(parenExpr))
+        << parenExpr->getSourceRange();
+    handled_.insert(parenExpr);
+    return true;
+}
+
+bool UnnecessaryParen::VisitCXXDeleteExpr(const CXXDeleteExpr* deleteExpr)
+{
+    if (ignoreLocation(deleteExpr))
+        return true;
+
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(deleteExpr->getArgument()));
+    if (!parenExpr)
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+    // assignments need extra parentheses or they generate a compiler warning
+    auto binaryOp = dyn_cast<BinaryOperator>(parenExpr->getSubExpr());
+    if (binaryOp && binaryOp->getOpcode() == BO_Assign)
+        return true;
+    report(
+        DiagnosticsEngine::Warning, "parentheses immediately inside delete expr",
+        compat::getBeginLoc(parenExpr))
+        << parenExpr->getSourceRange();
+    handled_.insert(parenExpr);
+    return true;
+}
+
+bool UnnecessaryParen::VisitCXXOperatorCallExpr(const CXXOperatorCallExpr* callExpr)
+{
+    if (ignoreLocation(callExpr))
+        return true;
+    if (callExpr->getNumArgs() != 2)
+        return true;
+
+    // Same logic as CXXOperatorCallExpr::isAssignmentOp(), which our supported clang
+    // doesn't have yet.
+    auto Opc = callExpr->getOperator();
+    if (Opc != OO_Equal && Opc != OO_StarEqual &&
+        Opc != OO_SlashEqual && Opc != OO_PercentEqual &&
+        Opc != OO_PlusEqual && Opc != OO_MinusEqual &&
+        Opc != OO_LessLessEqual && Opc != OO_GreaterGreaterEqual &&
+        Opc != OO_AmpEqual && Opc != OO_CaretEqual &&
+        Opc != OO_PipeEqual)
+        return true;
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(callExpr->getArg(1)));
+    if (!parenExpr)
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+    // Sometimes parentheses make the RHS of an assignment easier to read by
+    // visually disambiguating the = from a call to ==
+    auto sub = parenExpr->getSubExpr();
+    if (auto subBinOp = dyn_cast<BinaryOperator>(sub))
+    {
+        if (!(subBinOp->isMultiplicativeOp() || subBinOp->isAdditiveOp() || subBinOp->isPtrMemOp()))
+            return true;
+    }
+    if (auto subOperatorCall = dyn_cast<CXXOperatorCallExpr>(sub))
+    {
+        auto op = subOperatorCall->getOperator();
+        if (!((op >= OO_Plus && op <= OO_Exclaim) || (op >= OO_ArrowStar && op <= OO_Subscript)))
+            return true;
+    }
+    if (isa<ConditionalOperator>(sub))
+        return true;
+
+    report(
+        DiagnosticsEngine::Warning, "parentheses immediately inside assignment",
+        compat::getBeginLoc(parenExpr))
+        << parenExpr->getSourceRange();
+    handled_.insert(parenExpr);
+    return true;
+}
+
+bool UnnecessaryParen::VisitVarDecl(const VarDecl* varDecl)
+{
+    if (ignoreLocation(varDecl))
+        return true;
+    if (!varDecl->getInit())
+        return true;
+
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(varDecl->getInit()));
+    if (!parenExpr)
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+
+    // Sometimes parentheses make the RHS of an assignment easier to read by
+    // visually disambiguating the = from a call to ==
+    auto sub = parenExpr->getSubExpr();
+#if CLANG_VERSION >= 100000
+    if (auto const e = dyn_cast<CXXRewrittenBinaryOperator>(sub)) {
+        sub = e->getDecomposedForm().InnerBinOp;
+    }
+#endif
+    if (auto subBinOp = dyn_cast<BinaryOperator>(sub))
+    {
+        if (!(subBinOp->isMultiplicativeOp() || subBinOp->isAdditiveOp() || subBinOp->isPtrMemOp()))
+            return true;
+    }
+    if (auto subOperatorCall = dyn_cast<CXXOperatorCallExpr>(sub))
+    {
+        auto op = subOperatorCall->getOperator();
+        if (!((op >= OO_Plus && op <= OO_Exclaim) || (op >= OO_ArrowStar && op <= OO_Subscript)))
+            return true;
+    }
+    if (isa<ConditionalOperator>(sub))
+        return true;
+
+    // these two are for "parentheses were disambiguated as a function declaration [-Werror,-Wvexing-parse]"
+    auto const sub2 = sub->IgnoreImplicit();
+    if (isa<CXXTemporaryObjectExpr>(sub2)
+        || isa<CXXFunctionalCastExpr>(sub2))
+        return true;
+
+    report(
+        DiagnosticsEngine::Warning, "parentheses immediately inside vardecl statement",
+        compat::getBeginLoc(parenExpr))
+        << parenExpr->getSourceRange();
+    handled_.insert(parenExpr);
+    return true;
+}
+
+bool UnnecessaryParen::VisitMemberExpr(const MemberExpr* memberExpr)
+{
+    if (ignoreLocation(memberExpr))
+        return true;
+
+    auto parenExpr = dyn_cast<ParenExpr>(ignoreAllImplicit(memberExpr->getBase()));
+    if (!parenExpr)
+        return true;
+    if (handled_.find(parenExpr) != handled_.end())
+        return true;
+    if (compat::getBeginLoc(parenExpr).isMacroID())
+        return true;
+
+    auto sub = parenExpr->getSubExpr();
+    if (isa<CallExpr>(sub)) {
+        if (isa<CXXOperatorCallExpr>(sub))
+           return true;
+    } else if (isa<CXXConstructExpr>(sub)) {
+        // warn
+    } else if (isa<MemberExpr>(sub)) {
+        // warn
+    } else if (isa<DeclRefExpr>(sub)) {
+        // warn
+    } else
+        return true;
+
+    report(
+        DiagnosticsEngine::Warning, "unnecessary parentheses around member expr",
+        compat::getBeginLoc(parenExpr))
+        << parenExpr->getSourceRange();
+    handled_.insert(parenExpr);
+    return true;
+}
+
+// Conservatively assume any parenthesised integer or Boolean (incl. Objective-C ones) literal in
+// certain condition expressions (i.e., those for which handleUnreachableCodeConditionParens is
+// called) to be parenthesised to silence Clang -Wunreachable-code, if that is either the whole
+// condition expression or appears as a certain sub-expression (looking at what isConfigurationValue
+// in Clang's lib/Analysis/ReachableCode.cpp looks for, descending into certain unary and binary
+// operators):
+void UnnecessaryParen::handleUnreachableCodeConditionParens(Expr const * expr) {
+    // Cf. :
+    auto const e = ignoreAllImplicit(expr);
+    if (auto const e1 = dyn_cast<ParenExpr>(e)) {
+        auto const sub = e1->getSubExpr();
+        if (isa<IntegerLiteral>(sub) || isa<CXXBoolLiteralExpr>(sub)
+            || isa<ObjCBoolLiteralExpr>(sub))
+        {
+            handled_.insert(e1);
+        }
+    } else if (auto const e1 = dyn_cast<UnaryOperator>(e)) {
+        if (e1->getOpcode() == UO_LNot) {
+            handleUnreachableCodeConditionParens(e1->getSubExpr());
+        }
+    } else if (auto const e1 = dyn_cast<BinaryOperator>(e)) {
+        if (e1->isLogicalOp() || e1->isComparisonOp()) {
+            handleUnreachableCodeConditionParens(e1->getLHS());
+            handleUnreachableCodeConditionParens(e1->getRHS());
+        }
+    }
+}
+
+bool UnnecessaryParen::isPrecededBy_BAD_CAST(Expr const * expr) {
+    if (compat::getBeginLoc(expr).isMacroID()) {
+        return false;
+    }
+    SourceManager& SM = compiler.getSourceManager();
+    const char *p1 = SM.getCharacterData( compat::getBeginLoc(expr).getLocWithOffset(-10) );
+    const char *p2 = SM.getCharacterData( compat::getBeginLoc(expr) );
+    return std::string(p1, p2 - p1).find("BAD_CAST") != std::string::npos;
+}
+
+namespace {
+
+bool badCombinationChar(char c) {
+    return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '_'
+        || c == '+' || c == '-' || c == '\'' || c == '"';
+}
+
+}
+
+bool UnnecessaryParen::badCombination(SourceLocation loc, int prevOffset, int nextOffset) {
+    //TODO: check for start/end of file; take backslash-newline line concatenation into account
+    auto const c1
+        = compiler.getSourceManager().getCharacterData(loc.getLocWithOffset(prevOffset))[0];
+    auto const c2
+        = compiler.getSourceManager().getCharacterData(loc.getLocWithOffset(nextOffset))[0];
+    // An approximation of avoiding whatever combinations that would cause two adjacent tokens to be
+    // lexed differently, using, for now, letters (TODO: non-ASCII ones) and digits and '_'; '+' and
+    // '-' (to avoid ++, etc.); '\'' and '"' (to avoid u'x' or "foo"bar, etc.):
+    return badCombinationChar(c1) && badCombinationChar(c2);
+}
+
+bool UnnecessaryParen::removeParens(ParenExpr const * expr) {
+    if (rewriter == nullptr) {
+        return false;
+    }
+    auto const firstBegin = compat::getBeginLoc(expr);
+    auto secondBegin = compat::getEndLoc(expr);
+    if (firstBegin.isMacroID() || secondBegin.isMacroID()) {
+        return false;
+    }
+    unsigned firstLen = Lexer::MeasureTokenLength(
+        firstBegin, compiler.getSourceManager(), compiler.getLangOpts());
+    for (auto l = firstBegin.getLocWithOffset(std::max<unsigned>(firstLen, 1));;
+         l = l.getLocWithOffset(1))
+    {
+        unsigned n = Lexer::MeasureTokenLength(
+            l, compiler.getSourceManager(), compiler.getLangOpts());
+        if (n != 0) {
+            break;
+        }
+        ++firstLen;
+    }
+    unsigned secondLen = Lexer::MeasureTokenLength(
+        secondBegin, compiler.getSourceManager(), compiler.getLangOpts());
+    for (;;) {
+        auto l = secondBegin.getLocWithOffset(-1);
+        auto const c = compiler.getSourceManager().getCharacterData(l)[0];
+        if (c == '\n') {
+            if (compiler.getSourceManager().getCharacterData(l.getLocWithOffset(-1))[0] == '\\') {
+                break;
+            }
+        } else if (!(c == ' ' || c == '\t' || c == '\v' || c == '\f')) {
+            break;
+        }
+        secondBegin = l;
+        ++secondLen;
+    }
+    if (!replaceText(firstBegin, firstLen, badCombination(firstBegin, -1, firstLen) ? " " : "")) {
+        if (isDebugMode()) {
+            report(
+                DiagnosticsEngine::Fatal,
+                "TODO: cannot rewrite opening parenthesis, needs investigation",
+                firstBegin);
+            report(
+                DiagnosticsEngine::Note, "when removing these parentheses", expr->getExprLoc())
+                << expr->getSourceRange();
+        }
+        return false;
+    }
+    if (!replaceText(secondBegin, secondLen, badCombination(secondBegin, -1, secondLen) ? " " : ""))
+    {
+        //TODO: roll back first change
+        if (isDebugMode()) {
+            report(
+                DiagnosticsEngine::Fatal,
+                "TODO: cannot rewrite closing parenthesis, needs investigation",
+                secondBegin);
+            report(
+                DiagnosticsEngine::Note, "when removing these parentheses", expr->getExprLoc())
+                << expr->getSourceRange();
+        }
+        return false;
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration< UnnecessaryParen > unnecessaryparen("unnecessaryparen", true);
+
+}
+
+#endif // LO_CLANG_SHARED_PLUGINS
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */