[analyzer] Add ExprMutationAnalyzer

[shuaiwang]

Summary

This is 1/2 of moving ExprMutationAnalyzer from clangtidy to
clang/Analysis.
This diff along simply copies the ExprMutationAnalyzer over with trivial
modifications (e.g. include path, namespace)
2/2 will migrate existing usage of ExprMutationAnalyzer and remove the
original copy inside clangtidy.

[george.karpenkov]

Wow, thanks a lot, I'm really looking forward to using this!

[thakis]

Old review, but clang binary should not depend on ASTMatchers.

It's fine if ExprMutationAnalyzer isn't used within clang, but then it should go into a different library, not into clang/lib/Analysis, which is used by clang.

cfe/trunk/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h

+//===---------- ExprMutationAnalyzer.h ------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_EXPRMUTATIONANALYZER_H
+#define LLVM_CLANG_ANALYSIS_ANALYSES_EXPRMUTATIONANALYZER_H
+
+#include <type_traits>
+
+#include "clang/AST/AST.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "llvm/ADT/DenseMap.h"
+
+namespace clang {
+
+/// Analyzes whether any mutative operations are applied to an expression within
+/// a given statement.
+class ExprMutationAnalyzer {
+public:
+  ExprMutationAnalyzer(const Stmt &Stm, ASTContext &Context)
+      : Stm(Stm), Context(Context) {}
+
+  bool isMutated(const Decl *Dec) { return findDeclMutation(Dec) != nullptr; }
+  bool isMutated(const Expr *Exp) { return findMutation(Exp) != nullptr; }
+  const Stmt *findMutation(const Expr *Exp);
+
+private:
+  bool isUnevaluated(const Expr *Exp);
+
+  const Stmt *findExprMutation(ArrayRef<ast_matchers::BoundNodes> Matches);
+  const Stmt *findDeclMutation(ArrayRef<ast_matchers::BoundNodes> Matches);
+  const Stmt *findDeclMutation(const Decl *Dec);
+
+  const Stmt *findDirectMutation(const Expr *Exp);
+  const Stmt *findMemberMutation(const Expr *Exp);
+  const Stmt *findArrayElementMutation(const Expr *Exp);
+  const Stmt *findCastMutation(const Expr *Exp);
+  const Stmt *findRangeLoopMutation(const Expr *Exp);
+  const Stmt *findReferenceMutation(const Expr *Exp);
+
+  const Stmt &Stm;
+  ASTContext &Context;
+  llvm::DenseMap<const Expr *, const Stmt *> Results;
+};
+
+} // namespace clang
+
+#endif // LLVM_CLANG_ANALYSIS_ANALYSES_EXPRMUTATIONANALYZER_H

cfe/trunk/lib/Analysis/CMakeLists.txt

add_clang_library(clangAnalysis
   CFGStmtMap.cpp
   CallGraph.cpp
   CloneDetection.cpp
   CocoaConventions.cpp
   ConstructionContext.cpp
   Consumed.cpp
   CodeInjector.cpp
   Dominators.cpp
+  ExprMutationAnalyzer.cpp
   FormatString.cpp
   LiveVariables.cpp
   OSLog.cpp
   ObjCNoReturn.cpp
   PostOrderCFGView.cpp
   PrintfFormatString.cpp
   ProgramPoint.cpp
   PseudoConstantAnalysis.cpp

cfe/trunk/lib/Analysis/ExprMutationAnalyzer.cpp

+//===---------- ExprMutationAnalyzer.cpp ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/STLExtras.h"
+
+namespace clang {
+using namespace ast_matchers;
+
+namespace {
+
+AST_MATCHER_P(LambdaExpr, hasCaptureInit, const Expr *, E) {
+  return llvm::is_contained(Node.capture_inits(), E);
+}
+
+AST_MATCHER_P(CXXForRangeStmt, hasRangeStmt,
+              ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
+  const DeclStmt *const Range = Node.getRangeStmt();
+  return InnerMatcher.matches(*Range, Finder, Builder);
+}
+
+const ast_matchers::internal::VariadicDynCastAllOfMatcher<Stmt, CXXTypeidExpr>
+    cxxTypeidExpr;
+
+AST_MATCHER(CXXTypeidExpr, isPotentiallyEvaluated) {
+  return Node.isPotentiallyEvaluated();
+}
+
+const ast_matchers::internal::VariadicDynCastAllOfMatcher<Stmt, CXXNoexceptExpr>
+    cxxNoexceptExpr;
+
+const ast_matchers::internal::VariadicDynCastAllOfMatcher<Stmt,
+                                                          GenericSelectionExpr>
+    genericSelectionExpr;
+
+AST_MATCHER_P(GenericSelectionExpr, hasControllingExpr,
+              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
+  return InnerMatcher.matches(*Node.getControllingExpr(), Finder, Builder);
+}
+
+const auto nonConstReferenceType = [] {
+  return hasUnqualifiedDesugaredType(
+      referenceType(pointee(unless(isConstQualified()))));
+};
+
+const auto nonConstPointerType = [] {
+  return hasUnqualifiedDesugaredType(
+      pointerType(pointee(unless(isConstQualified()))));
+};
+
+const auto isMoveOnly = [] {
+  return cxxRecordDecl(
+      hasMethod(cxxConstructorDecl(isMoveConstructor(), unless(isDeleted()))),
+      hasMethod(cxxMethodDecl(isMoveAssignmentOperator(), unless(isDeleted()))),
+      unless(anyOf(hasMethod(cxxConstructorDecl(isCopyConstructor(),
+                                                unless(isDeleted()))),
+                   hasMethod(cxxMethodDecl(isCopyAssignmentOperator(),
+                                           unless(isDeleted()))))));
+};
+
+} // namespace
+
+const Stmt *ExprMutationAnalyzer::findMutation(const Expr *Exp) {
+  const auto Memoized = Results.find(Exp);
+  if (Memoized != Results.end())
+    return Memoized->second;
+
+  if (isUnevaluated(Exp))
+    return Results[Exp] = nullptr;
+
+  for (const auto &Finder : {&ExprMutationAnalyzer::findDirectMutation,
+                             &ExprMutationAnalyzer::findMemberMutation,
+                             &ExprMutationAnalyzer::findArrayElementMutation,
+                             &ExprMutationAnalyzer::findCastMutation,
+                             &ExprMutationAnalyzer::findRangeLoopMutation,
+                             &ExprMutationAnalyzer::findReferenceMutation}) {
+    if (const Stmt *S = (this->*Finder)(Exp))
+      return Results[Exp] = S;
+  }
+
+  return Results[Exp] = nullptr;
+}
+
+bool ExprMutationAnalyzer::isUnevaluated(const Expr *Exp) {
+  return selectFirst<Expr>(
+             "expr",
+             match(
+                 findAll(
+                     expr(equalsNode(Exp),
+                          anyOf(
+                              // `Exp` is part of the underlying expression of
+                              // decltype/typeof if it has an ancestor of
+                              // typeLoc.
+                              hasAncestor(typeLoc(unless(
+                                  hasAncestor(unaryExprOrTypeTraitExpr())))),
+                              hasAncestor(expr(anyOf(
+                                  // `UnaryExprOrTypeTraitExpr` is unevaluated
+                                  // unless it's sizeof on VLA.
+                                  unaryExprOrTypeTraitExpr(unless(sizeOfExpr(
+                                      hasArgumentOfType(variableArrayType())))),
+                                  // `CXXTypeidExpr` is unevaluated unless it's
+                                  // applied to an expression of glvalue of
+                                  // polymorphic class type.
+                                  cxxTypeidExpr(
+                                      unless(isPotentiallyEvaluated())),
+                                  // The controlling expression of
+                                  // `GenericSelectionExpr` is unevaluated.
+                                  genericSelectionExpr(hasControllingExpr(
+                                      hasDescendant(equalsNode(Exp)))),
+                                  cxxNoexceptExpr())))))
+                         .bind("expr")),
+                 Stm, Context)) != nullptr;
+}
+
+const Stmt *
+ExprMutationAnalyzer::findExprMutation(ArrayRef<BoundNodes> Matches) {
+  for (const auto &Nodes : Matches) {
+    if (const Stmt *S = findMutation(Nodes.getNodeAs<Expr>("expr")))
+      return S;
+  }
+  return nullptr;
+}
+
+const Stmt *
+ExprMutationAnalyzer::findDeclMutation(ArrayRef<BoundNodes> Matches) {
+  for (const auto &DeclNodes : Matches) {
+    if (const Stmt *S = findDeclMutation(DeclNodes.getNodeAs<Decl>("decl")))
+      return S;
+  }
+  return nullptr;
+}
+
+const Stmt *ExprMutationAnalyzer::findDeclMutation(const Decl *Dec) {
+  const auto Refs = match(
+      findAll(declRefExpr(to(equalsNode(Dec))).bind("expr")), Stm, Context);
+  for (const auto &RefNodes : Refs) {
+    const auto *E = RefNodes.getNodeAs<Expr>("expr");
+    if (findMutation(E))
+      return E;
+  }
+  return nullptr;
+}
+
+const Stmt *ExprMutationAnalyzer::findDirectMutation(const Expr *Exp) {
+  // LHS of any assignment operators.
+  const auto AsAssignmentLhs =
+      binaryOperator(isAssignmentOperator(), hasLHS(equalsNode(Exp)));
+
+  // Operand of increment/decrement operators.
+  const auto AsIncDecOperand =
+      unaryOperator(anyOf(hasOperatorName("++"), hasOperatorName("--")),
+                    hasUnaryOperand(equalsNode(Exp)));
+
+  // Invoking non-const member function.
+  // A member function is assumed to be non-const when it is unresolved.
+  const auto NonConstMethod = cxxMethodDecl(unless(isConst()));
+  const auto AsNonConstThis =
+      expr(anyOf(cxxMemberCallExpr(callee(NonConstMethod), on(equalsNode(Exp))),
+                 cxxOperatorCallExpr(callee(NonConstMethod),
+                                     hasArgument(0, equalsNode(Exp))),
+                 callExpr(callee(expr(anyOf(
+                     unresolvedMemberExpr(hasObjectExpression(equalsNode(Exp))),
+                     cxxDependentScopeMemberExpr(
+                         hasObjectExpression(equalsNode(Exp)))))))));
+
+  // Taking address of 'Exp'.
+  // We're assuming 'Exp' is mutated as soon as its address is taken, though in
+  // theory we can follow the pointer and see whether it escaped `Stm` or is
+  // dereferenced and then mutated. This is left for future improvements.
+  const auto AsAmpersandOperand =
+      unaryOperator(hasOperatorName("&"),
+                    // A NoOp implicit cast is adding const.
+                    unless(hasParent(implicitCastExpr(hasCastKind(CK_NoOp)))),
+                    hasUnaryOperand(equalsNode(Exp)));
+  const auto AsPointerFromArrayDecay =
+      castExpr(hasCastKind(CK_ArrayToPointerDecay),
+               unless(hasParent(arraySubscriptExpr())), has(equalsNode(Exp)));
+  // Treat calling `operator->()` of move-only classes as taking address.
+  // These are typically smart pointers with unique ownership so we treat
+  // mutation of pointee as mutation of the smart pointer itself.
+  const auto AsOperatorArrowThis =
+      cxxOperatorCallExpr(hasOverloadedOperatorName("->"),
+                          callee(cxxMethodDecl(ofClass(isMoveOnly()),
+                                               returns(nonConstPointerType()))),
+                          argumentCountIs(1), hasArgument(0, equalsNode(Exp)));
+
+  // Used as non-const-ref argument when calling a function.
+  // An argument is assumed to be non-const-ref when the function is unresolved.
+  const auto NonConstRefParam = forEachArgumentWithParam(
+      equalsNode(Exp), parmVarDecl(hasType(nonConstReferenceType())));
+  const auto AsNonConstRefArg = anyOf(
+      callExpr(NonConstRefParam), cxxConstructExpr(NonConstRefParam),
+      callExpr(callee(expr(anyOf(unresolvedLookupExpr(), unresolvedMemberExpr(),
+                                 cxxDependentScopeMemberExpr(),
+                                 hasType(templateTypeParmType())))),
+               hasAnyArgument(equalsNode(Exp))),
+      cxxUnresolvedConstructExpr(hasAnyArgument(equalsNode(Exp))));
+
+  // Captured by a lambda by reference.
+  // If we're initializing a capture with 'Exp' directly then we're initializing
+  // a reference capture.
+  // For value captures there will be an ImplicitCastExpr <LValueToRValue>.
+  const auto AsLambdaRefCaptureInit = lambdaExpr(hasCaptureInit(Exp));
+
+  // Returned as non-const-ref.
+  // If we're returning 'Exp' directly then it's returned as non-const-ref.
+  // For returning by value there will be an ImplicitCastExpr <LValueToRValue>.
+  // For returning by const-ref there will be an ImplicitCastExpr <NoOp> (for
+  // adding const.)
+  const auto AsNonConstRefReturn = returnStmt(hasReturnValue(equalsNode(Exp)));
+
+  const auto Matches =
+      match(findAll(stmt(anyOf(AsAssignmentLhs, AsIncDecOperand, AsNonConstThis,
+                               AsAmpersandOperand, AsPointerFromArrayDecay,
+                               AsOperatorArrowThis, AsNonConstRefArg,
+                               AsLambdaRefCaptureInit, AsNonConstRefReturn))
+                        .bind("stmt")),
+            Stm, Context);
+  return selectFirst<Stmt>("stmt", Matches);
+}
+
+const Stmt *ExprMutationAnalyzer::findMemberMutation(const Expr *Exp) {
+  // Check whether any member of 'Exp' is mutated.
+  const auto MemberExprs =
+      match(findAll(expr(anyOf(memberExpr(hasObjectExpression(equalsNode(Exp))),
+                               cxxDependentScopeMemberExpr(
+                                   hasObjectExpression(equalsNode(Exp)))))
+                        .bind("expr")),
+            Stm, Context);
+  return findExprMutation(MemberExprs);
+}
+
+const Stmt *ExprMutationAnalyzer::findArrayElementMutation(const Expr *Exp) {
+  // Check whether any element of an array is mutated.
+  const auto SubscriptExprs = match(
+      findAll(arraySubscriptExpr(hasBase(ignoringImpCasts(equalsNode(Exp))))
+                  .bind("expr")),
+      Stm, Context);
+  return findExprMutation(SubscriptExprs);
+}
+
+const Stmt *ExprMutationAnalyzer::findCastMutation(const Expr *Exp) {
+  // If 'Exp' is casted to any non-const reference type, check the castExpr.
+  const auto Casts =
+      match(findAll(castExpr(hasSourceExpression(equalsNode(Exp)),
+                             anyOf(explicitCastExpr(hasDestinationType(
+                                       nonConstReferenceType())),
+                                   implicitCastExpr(hasImplicitDestinationType(
+                                       nonConstReferenceType()))))
+                        .bind("expr")),
+            Stm, Context);
+  return findExprMutation(Casts);
+}
+
+const Stmt *ExprMutationAnalyzer::findRangeLoopMutation(const Expr *Exp) {
+  // If range for looping over 'Exp' with a non-const reference loop variable,
+  // check all declRefExpr of the loop variable.
+  const auto LoopVars =
+      match(findAll(cxxForRangeStmt(
+                hasLoopVariable(
+                    varDecl(hasType(nonConstReferenceType())).bind("decl")),
+                hasRangeInit(equalsNode(Exp)))),
+            Stm, Context);
+  return findDeclMutation(LoopVars);
+}
+
+const Stmt *ExprMutationAnalyzer::findReferenceMutation(const Expr *Exp) {
+  // Follow non-const reference returned by `operator*()` of move-only classes.
+  // These are typically smart pointers with unique ownership so we treat
+  // mutation of pointee as mutation of the smart pointer itself.
+  const auto Ref = match(
+      findAll(cxxOperatorCallExpr(
+                  hasOverloadedOperatorName("*"),
+                  callee(cxxMethodDecl(ofClass(isMoveOnly()),
+                                       returns(hasUnqualifiedDesugaredType(
+                                           nonConstReferenceType())))),
+                  argumentCountIs(1), hasArgument(0, equalsNode(Exp)))
+                  .bind("expr")),
+      Stm, Context);
+  if (const Stmt *S = findExprMutation(Ref))
+    return S;
+
+  // If 'Exp' is bound to a non-const reference, check all declRefExpr to that.
+  const auto Refs = match(
+      stmt(forEachDescendant(
+          varDecl(
+              hasType(nonConstReferenceType()),
+              hasInitializer(anyOf(equalsNode(Exp),
+                                   conditionalOperator(anyOf(
+                                       hasTrueExpression(equalsNode(Exp)),
+                                       hasFalseExpression(equalsNode(Exp)))))),
+              hasParent(declStmt().bind("stmt")),
+              // Don't follow the reference in range statement, we've handled
+              // that separately.
+              unless(hasParent(declStmt(hasParent(
+                  cxxForRangeStmt(hasRangeStmt(equalsBoundNode("stmt"))))))))
+              .bind("decl"))),
+      Stm, Context);
+  return findDeclMutation(Refs);
+}
+
+} // namespace clang

cfe/trunk/unittests/Analysis/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Support
   )
 
 add_clang_unittest(ClangAnalysisTests
   CFGTest.cpp
   CloneDetectionTest.cpp
+  ExprMutationAnalyzerTest.cpp
   )
 
 target_link_libraries(ClangAnalysisTests
   PRIVATE
   clangAnalysis
   clangAST
   clangASTMatchers
   clangBasic
   clangFrontend
   clangTooling
   )

cfe/trunk/unittests/Analysis/ExprMutationAnalyzerTest.cpp

+//===---------- ExprMutationAnalyzerTest.cpp ------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Tooling/Tooling.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include <cctype>
+
+namespace clang {
+
+using namespace clang::ast_matchers;
+using ::testing::ElementsAre;
+using ::testing::IsEmpty;
+using ::testing::ResultOf;
+using ::testing::StartsWith;
+using ::testing::Values;
+
+namespace {
+
+using ExprMatcher = internal::Matcher<Expr>;
+using StmtMatcher = internal::Matcher<Stmt>;
+
+ExprMatcher declRefTo(StringRef Name) {
+  return declRefExpr(to(namedDecl(hasName(Name))));
+}
+
+StmtMatcher withEnclosingCompound(ExprMatcher Matcher) {
+  return expr(Matcher, hasAncestor(compoundStmt().bind("stmt"))).bind("expr");
+}
+
+bool isMutated(const SmallVectorImpl<BoundNodes> &Results, ASTUnit *AST) {
+  const auto *const S = selectFirst<Stmt>("stmt", Results);
+  const auto *const E = selectFirst<Expr>("expr", Results);
+  return ExprMutationAnalyzer(*S, AST->getASTContext()).isMutated(E);
+}
+
+SmallVector<std::string, 1>
+mutatedBy(const SmallVectorImpl<BoundNodes> &Results, ASTUnit *AST) {
+  const auto *const S = selectFirst<Stmt>("stmt", Results);
+  SmallVector<std::string, 1> Chain;
+  ExprMutationAnalyzer Analyzer(*S, AST->getASTContext());
+  for (const auto *E = selectFirst<Expr>("expr", Results); E != nullptr;) {
+    const Stmt *By = Analyzer.findMutation(E);
+    std::string buffer;
+    llvm::raw_string_ostream stream(buffer);
+    By->printPretty(stream, nullptr, AST->getASTContext().getPrintingPolicy());
+    Chain.push_back(StringRef(stream.str()).trim().str());
+    E = dyn_cast<DeclRefExpr>(By);
+  }
+  return Chain;
+}
+
+std::string removeSpace(std::string s) {
+  s.erase(std::remove_if(s.begin(), s.end(),
+                         [](char c) { return std::isspace(c); }),
+          s.end());
+  return s;
+}
+
+} // namespace
+
+TEST(ExprMutationAnalyzerTest, Trivial) {
+  const auto AST = tooling::buildASTFromCode("void f() { int x; x; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+class AssignmentTest : public ::testing::TestWithParam<std::string> {};
+
+TEST_P(AssignmentTest, AssignmentModifies) {
+  const std::string ModExpr = "x " + GetParam() + " 10";
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; " + ModExpr + "; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre(ModExpr));
+}
+
+INSTANTIATE_TEST_CASE_P(AllAssignmentOperators, AssignmentTest,
+                        Values("=", "+=", "-=", "*=", "/=", "%=", "&=", "|=",
+                               "^=", "<<=", ">>="), );
+
+class IncDecTest : public ::testing::TestWithParam<std::string> {};
+
+TEST_P(IncDecTest, IncDecModifies) {
+  const std::string ModExpr = GetParam();
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; " + ModExpr + "; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre(ModExpr));
+}
+
+INSTANTIATE_TEST_CASE_P(AllIncDecOperators, IncDecTest,
+                        Values("++x", "--x", "x++", "x--"), );
+
+TEST(ExprMutationAnalyzerTest, NonConstMemberFunc) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { struct Foo { void mf(); }; Foo x; x.mf(); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.mf()"));
+}
+
+TEST(ExprMutationAnalyzerTest, AssumedNonConstMemberFunc) {
+  auto AST = tooling::buildASTFromCodeWithArgs(
+      "struct X { template <class T> void mf(); };"
+      "template <class T> void f() { X x; x.mf<T>(); }",
+      {"-fno-delayed-template-parsing"});
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.mf<T>()"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f() { T x; x.mf(); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.mf()"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> struct X;"
+      "template <class T> void f() { X<T> x; x.mf(); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.mf()"));
+}
+
+TEST(ExprMutationAnalyzerTest, ConstMemberFunc) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { struct Foo { void mf() const; }; Foo x; x.mf(); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, NonConstOperator) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { struct Foo { Foo& operator=(int); }; Foo x; x = 10; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, ConstOperator) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { struct Foo { int operator()() const; }; Foo x; x(); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ByValueArgument) {
+  auto AST =
+      tooling::buildASTFromCode("void g(int); void f() { int x; g(x); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void g(int*); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("typedef int* IntPtr;"
+                                  "void g(IntPtr); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(A, int); A x; x + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(int); }; int x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(); A(A); }; A x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ByConstValueArgument) {
+  auto AST =
+      tooling::buildASTFromCode("void g(const int); void f() { int x; g(x); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void g(int* const); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST =
+      tooling::buildASTFromCode("typedef int* const CIntPtr;"
+                                "void g(CIntPtr); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(const A, int); A x; x + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(const int); }; int x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(); A(const A); }; A x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ByNonConstRefArgument) {
+  auto AST =
+      tooling::buildASTFromCode("void g(int&); void f() { int x; g(x); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCode("typedef int& IntRef;"
+                                  "void g(IntRef); void f() { int x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST =
+      tooling::buildASTFromCode("template <class T> using TRef = T&;"
+                                "void g(TRef<int>); void f() { int x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCode(
+      "template <class T> struct identity { using type = T; };"
+      "template <class T, class U = T&> void g(typename identity<U>::type);"
+      "void f() { int x; g<int>(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g<int>(x)"));
+
+  AST =
+      tooling::buildASTFromCode("typedef int* IntPtr;"
+                                "void g(IntPtr&); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCode(
+      "typedef int* IntPtr; typedef IntPtr& IntPtrRef;"
+      "void g(IntPtrRef); void f() { int* x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(A&, int); A x; x + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x + 1"));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(int&); }; int x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x"));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(); A(A&); }; A x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x"));
+}
+
+TEST(ExprMutationAnalyzerTest, ByConstRefArgument) {
+  auto AST = tooling::buildASTFromCode(
+      "void g(const int&); void f() { int x; g(x); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("typedef const int& CIntRef;"
+                                  "void g(CIntRef); void f() { int x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "template <class T> using CTRef = const T&;"
+      "void g(CTRef<int>); void f() { int x; g(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "template <class T> struct identity { using type = T; };"
+      "template <class T, class U = const T&>"
+      "void g(typename identity<U>::type);"
+      "void f() { int x; g<int>(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(const A&, int); A x; x + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(const int&); }; int x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A { A(); A(const A&); }; A x; A y(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ByNonConstRRefArgument) {
+  auto AST = tooling::buildASTFromCode(
+      "void g(int&&); void f() { int x; g(static_cast<int &&>(x)); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("g(static_cast<int &&>(x))"));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(A&&, int); "
+      "A x; static_cast<A &&>(x) + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("static_cast<A &&>(x) + 1"));
+
+  AST = tooling::buildASTFromCode("void f() { struct A { A(int&&); }; "
+                                  "int x; A y(static_cast<int &&>(x)); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("static_cast<int &&>(x)"));
+
+  AST = tooling::buildASTFromCode("void f() { struct A { A(); A(A&&); }; "
+                                  "A x; A y(static_cast<A &&>(x)); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("static_cast<A &&>(x)"));
+}
+
+TEST(ExprMutationAnalyzerTest, ByConstRRefArgument) {
+  auto AST = tooling::buildASTFromCode(
+      "void g(const int&&); void f() { int x; g(static_cast<int&&>(x)); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { struct A {}; A operator+(const A&&, int); "
+      "A x; static_cast<A&&>(x) + 1; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void f() { struct A { A(const int&&); }; "
+                                  "int x; A y(static_cast<int&&>(x)); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void f() { struct A { A(); A(const A&&); }; "
+                                  "A x; A y(static_cast<A&&>(x)); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, Move) {
+  // Technically almost the same as ByNonConstRRefArgument, just double checking
+  const auto AST = tooling::buildASTFromCode(
+      "namespace std {"
+      "template<class T> struct remove_reference { typedef T type; };"
+      "template<class T> struct remove_reference<T&> { typedef T type; };"
+      "template<class T> struct remove_reference<T&&> { typedef T type; };"
+      "template<class T> typename std::remove_reference<T>::type&& "
+      "move(T&& t) noexcept; }"
+      "void f() { struct A {}; A x; std::move(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("std::move(x)"));
+}
+
+TEST(ExprMutationAnalyzerTest, Forward) {
+  // Technically almost the same as ByNonConstRefArgument, just double checking
+  const auto AST = tooling::buildASTFromCode(
+      "namespace std {"
+      "template<class T> struct remove_reference { typedef T type; };"
+      "template<class T> struct remove_reference<T&> { typedef T type; };"
+      "template<class T> struct remove_reference<T&&> { typedef T type; };"
+      "template<class T> T&& "
+      "forward(typename std::remove_reference<T>::type&) noexcept;"
+      "template<class T> T&& "
+      "forward(typename std::remove_reference<T>::type&&) noexcept;"
+      "void f() { struct A {}; A x; std::forward<A &>(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("std::forward<A &>(x)"));
+}
+
+TEST(ExprMutationAnalyzerTest, CallUnresolved) {
+  auto AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f() { T x; g(x); }",
+      {"-fno-delayed-template-parsing"});
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <int N> void f() { char x[N]; g(x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f(T t) { int x; g(t, x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(t, x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f(T t) { int x; t.mf(x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("t.mf(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> struct S;"
+      "template <class T> void f() { S<T> s; int x; s.mf(x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("s.mf(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "struct S { template <class T> void mf(); };"
+      "template <class T> void f(S s) { int x; s.mf<T>(x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("s.mf<T>(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs("template <class F>"
+                                          "void g(F f) { int x; f(x); } ",
+                                          {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("f(x)"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f() { int x; (void)T(x); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("T(x)"));
+}
+
+TEST(ExprMutationAnalyzerTest, ReturnAsValue) {
+  auto AST = tooling::buildASTFromCode("int f() { int x; return x; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("int* f() { int* x; return x; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("typedef int* IntPtr;"
+                                  "IntPtr f() { int* x; return x; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ReturnAsNonConstRef) {
+  const auto AST = tooling::buildASTFromCode("int& f() { int x; return x; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("return x;"));
+}
+
+TEST(ExprMutationAnalyzerTest, ReturnAsConstRef) {
+  const auto AST =
+      tooling::buildASTFromCode("const int& f() { int x; return x; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ReturnAsNonConstRRef) {
+  const auto AST = tooling::buildASTFromCode(
+      "int&& f() { int x; return static_cast<int &&>(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("return static_cast<int &&>(x);"));
+}
+
+TEST(ExprMutationAnalyzerTest, ReturnAsConstRRef) {
+  const auto AST = tooling::buildASTFromCode(
+      "const int&& f() { int x; return static_cast<int&&>(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, TakeAddress) {
+  const auto AST =
+      tooling::buildASTFromCode("void g(int*); void f() { int x; g(&x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("&x"));
+}
+
+TEST(ExprMutationAnalyzerTest, ArrayToPointerDecay) {
+  const auto AST =
+      tooling::buildASTFromCode("void g(int*); void f() { int x[2]; g(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x"));
+}
+
+TEST(ExprMutationAnalyzerTest, TemplateWithArrayToPointerDecay) {
+  const auto AST = tooling::buildASTFromCodeWithArgs(
+      "template <typename T> struct S { static constexpr int v = 8; };"
+      "template <> struct S<int> { static constexpr int v = 4; };"
+      "void g(char*);"
+      "template <typename T> void f() { char x[S<T>::v]; g(x); }"
+      "template <> void f<int>() { char y[S<int>::v]; g(y); }",
+      {"-fno-delayed-template-parsing"});
+  const auto ResultsX =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(ResultsX, AST.get()), ElementsAre("g(x)"));
+  const auto ResultsY =
+      match(withEnclosingCompound(declRefTo("y")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(ResultsY, AST.get()), ElementsAre("y"));
+}
+
+TEST(ExprMutationAnalyzerTest, FollowRefModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x; int& r0 = x; int& r1 = r0; int& r2 = r1; "
+      "int& r3 = r2; r3 = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("r0", "r1", "r2", "r3", "r3 = 10"));
+
+  AST = tooling::buildASTFromCode(
+      "typedef int& IntRefX;"
+      "using IntRefY = int&;"
+      "void f() { int x; IntRefX r0 = x; IntRefY r1 = r0;"
+      "decltype((x)) r2 = r1; r2 = 10; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("r0", "r1", "r2", "r2 = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, FollowRefNotModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x; int& r0 = x; int& r1 = r0; int& r2 = r1; "
+      "int& r3 = r2; int& r4 = r3; int& r5 = r4;}");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { int x; int& r0 = x; const int& r1 = r0;}");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "typedef const int& CIntRefX;"
+      "using CIntRefY = const int&;"
+      "void f() { int x; int& r0 = x; CIntRefX r1 = r0;"
+      "CIntRefY r2 = r1; decltype((r1)) r3 = r2;}");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, FollowConditionalRefModified) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { int x, y; bool b; int &r = b ? x : y; r = 10; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("r", "r = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, FollowConditionalRefNotModified) {
+  const auto AST = tooling::buildASTFromCode(
+      "void f() { int x, y; bool b; int& r = b ? x : y; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, ArrayElementModified) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x[2]; x[0] = 10; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x[0] = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, ArrayElementNotModified) {
+  const auto AST = tooling::buildASTFromCode("void f() { int x[2]; x[0]; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, NestedMemberModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { struct A { int vi; }; struct B { A va; }; "
+      "struct C { B vb; }; C x; x.vb.va.vi = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.vb.va.vi = 10"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f() { T x; x.y.z = 10; }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.y.z = 10"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> struct S;"
+      "template <class T> void f() { S<T> x; x.y.z = 10; }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.y.z = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, NestedMemberNotModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { struct A { int vi; }; struct B { A va; }; "
+      "struct C { B vb; }; C x; x.vb.va.vi; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> void f() { T x; x.y.z; }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "template <class T> struct S;"
+      "template <class T> void f() { S<T> x; x.y.z; }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, CastToValue) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; static_cast<double>(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, CastToRefModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x; static_cast<int &>(x) = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("static_cast<int &>(x) = 10"));
+
+  AST = tooling::buildASTFromCode(
+      "typedef int& IntRef;"
+      "void f() { int x; static_cast<IntRef>(x) = 10; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre("static_cast<IntRef>(x) = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, CastToRefNotModified) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; static_cast<int&>(x); }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, CastToConstRef) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x; static_cast<const int&>(x); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST =
+      tooling::buildASTFromCode("typedef const int& CIntRef;"
+                                "void f() { int x; static_cast<CIntRef>(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, LambdaDefaultCaptureByValue) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; [=]() { x = 10; }; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, LambdaExplicitCaptureByValue) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; [x]() { x = 10; }; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, LambdaDefaultCaptureByRef) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; [&]() { x = 10; }; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre(ResultOf(removeSpace, "[&](){x=10;}")));
+}
+
+TEST(ExprMutationAnalyzerTest, LambdaExplicitCaptureByRef) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x; [&x]() { x = 10; }; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()),
+              ElementsAre(ResultOf(removeSpace, "[&x](){x=10;}")));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForArrayByRefModified) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x[2]; for (int& e : x) e = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("e", "e = 10"));
+
+  AST = tooling::buildASTFromCode(
+      "typedef int& IntRef;"
+      "void f() { int x[2]; for (IntRef e : x) e = 10; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("e", "e = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForArrayByRefNotModified) {
+  const auto AST =
+      tooling::buildASTFromCode("void f() { int x[2]; for (int& e : x) e; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForArrayByValue) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x[2]; for (int e : x) e = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { int* x[2]; for (int* e : x) e = nullptr; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "typedef int* IntPtr;"
+      "void f() { int* x[2]; for (IntPtr e : x) e = nullptr; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForArrayByConstRef) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x[2]; for (const int& e : x) e; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "typedef const int& CIntRef;"
+      "void f() { int x[2]; for (CIntRef e : x) e; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForNonArrayByRefModified) {
+  const auto AST =
+      tooling::buildASTFromCode("struct V { int* begin(); int* end(); };"
+                                "void f() { V x; for (int& e : x) e = 10; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("e", "e = 10"));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForNonArrayByRefNotModified) {
+  const auto AST =
+      tooling::buildASTFromCode("struct V { int* begin(); int* end(); };"
+                                "void f() { V x; for (int& e : x) e; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForNonArrayByValue) {
+  const auto AST = tooling::buildASTFromCode(
+      "struct V { const int* begin() const; const int* end() const; };"
+      "void f() { V x; for (int e : x) e; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, RangeForNonArrayByConstRef) {
+  const auto AST = tooling::buildASTFromCode(
+      "struct V { const int* begin() const; const int* end() const; };"
+      "void f() { V x; for (const int& e : x) e; }");
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, UnevaluatedExpressions) {
+  auto AST = tooling::buildASTFromCode(
+      "void f() { int x, y; decltype(x = 10) z = y; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { int x, y; __typeof(x = 10) z = y; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { int x, y; __typeof__(x = 10) z = y; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void f() { int x; sizeof(x = 10); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void f() { int x; alignof(x = 10); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode("void f() { int x; noexcept(x = 10); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCodeWithArgs("namespace std { class type_info; }"
+                                          "void f() { int x; typeid(x = 10); }",
+                                          {"-frtti"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(
+      "void f() { int x; _Generic(x = 10, int: 0, default: 1); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+}
+
+TEST(ExprMutationAnalyzerTest, NotUnevaluatedExpressions) {
+  auto AST = tooling::buildASTFromCode("void f() { int x; sizeof(int[x++]); }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x++"));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      "namespace std { class type_info; }"
+      "struct A { virtual ~A(); }; struct B : A {};"
+      "struct X { A& f(); }; void f() { X x; typeid(x.f()); }",
+      {"-frtti"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x.f()"));
+}
+
+TEST(ExprMutationAnalyzerTest, UniquePtr) {
+  const std::string UniquePtrDef =
+      "template <class T> struct UniquePtr {"
+      "  UniquePtr();"
+      "  UniquePtr(const UniquePtr&) = delete;"
+      "  UniquePtr(UniquePtr&&);"
+      "  UniquePtr& operator=(const UniquePtr&) = delete;"
+      "  UniquePtr& operator=(UniquePtr&&);"
+      "  T& operator*() const;"
+      "  T* operator->() const;"
+      "};";
+
+  auto AST = tooling::buildASTFromCode(
+      UniquePtrDef + "void f() { UniquePtr<int> x; *x = 10; }");
+  auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("* x = 10"));
+
+  AST = tooling::buildASTFromCode(UniquePtrDef +
+                                  "void f() { UniquePtr<int> x; *x; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(UniquePtrDef +
+                                  "void f() { UniquePtr<const int> x; *x; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(UniquePtrDef +
+                                  "struct S { int v; };"
+                                  "void f() { UniquePtr<S> x; x->v; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x"));
+
+  AST = tooling::buildASTFromCode(UniquePtrDef +
+                                  "struct S { int v; };"
+                                  "void f() { UniquePtr<const S> x; x->v; }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCode(UniquePtrDef +
+                                  "struct S { void mf(); };"
+                                  "void f() { UniquePtr<S> x; x->mf(); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x"));
+
+  AST = tooling::buildASTFromCode(
+      UniquePtrDef + "struct S { void mf() const; };"
+                     "void f() { UniquePtr<const S> x; x->mf(); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = tooling::buildASTFromCodeWithArgs(
+      UniquePtrDef + "template <class T> void f() { UniquePtr<T> x; x->mf(); }",
+      {"-fno-delayed-template-parsing"});
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("x->mf()"));
+}
+
+} // namespace clang