[clang-tidy] implement utility-function to add 'const' to variables

[JonasToth]

Summary

This patch extends the already existing facility to add 'const' to variables
to be more flexible and correct. The previous version did not consider pointers
as value AND pointee. For future automatic introduction for const-correctness
this shortcoming needs to be fixed.
It always allows configuration where the 'const' token is inserted, either on
the left side (if possible) or the right side.
It adds many unit-tests to the utility-function that did not exist before, as
the function was implicitly tested through clang-tidy checks. These
tests were not changed, as the API is still compatible.

[alexfh]

unittests/clang-tidy/AddConstTest.cpp

733 ↗

(On Diff #173569)

It would be interesting to see test cases with multiple instantiations of the template the fix applies to.

[JonasToth]

add tests for different template instantiations

[JonasToth]

unittests/clang-tidy/AddConstTest.cpp

733 ↗

(On Diff #173569)

I added test for a template function with many instantiations, but there should not be a difference between the instantiations, because only the original code would be transformed, and there the 'how it looks' counts, so in this case it will be treated as a value.
Did I misinterpret your question?

[JonasToth]

reabse to master + ping :)

[lebedev.ri]

Looks reasonable to me (or at least all these tests make this look good :)), but i'm not sure i can fully review this.

[JonasToth]

In D54395#1309423, @lebedev.ri wrote:

Looks reasonable to me (or at least all these tests make this look good :)), but i'm not sure i can fully review this.

No problem ;)

[aaron.ballman]

clang-tidy/utils/FixItHintUtils.cpp

35 ↗

(On Diff #175444)

This file is replicating a bunch of functionality that exists on the Type* already. Why do this rather than have the caller do QT->isArrayType() and skip this function entirely? (Same exists elsewhere here.)

109 ↗

(On Diff #175444)

always right -> always to the right

clang-tidy/utils/FixItHintUtils.h

47 ↗

(On Diff #175444)

I feel like this could be trivially generalized to any type qualifier, not just const. How would you feel about renaming this to: addQualifierToVarDecl() and adding a parameter of type DeclSpec::TQ to specify which qualifier to add?

[JonasToth]

clang-tidy/utils/FixItHintUtils.cpp

35 ↗

(On Diff #175444)

I had the issue that typedefs are resolved, but shouldn't. If I am not mistaken QT->isArrayType() would go to the canconical type.

using MyPtr = int*;
MyPtr foo = nullptr;

Is treated wrong in that case.

clang-tidy/utils/FixItHintUtils.h

47 ↗

(On Diff #175444)

Yes, sounds good.

[JonasToth]

• generalize to DeclSpec::TQ
• add dependent type-tests with typename

[JonasToth]

ping :)

[JonasToth]

ping.

[JonasToth]

ping

[JonasToth]

another ping. @alexfh and @aaron.ballman you commented on prior versions. Would be nice if you could take a (final) look at this patch!

[alexfh]

A few more comments.

clang-tidy/utils/FixItHintUtils.cpp

83 ↗

(On Diff #182345)

The first operand being llvm::Twine is enough for the whole chained concatenation expression to be llvm::Twine.

unittests/clang-tidy/AddConstTest.cpp

15 ↗

(On Diff #182345)

What's the point of default values of template arguments here?

53 ↗

(On Diff #182345)

Is this still needed? If yes, please use "FIXME" instead and expand on what exactly is missing or needs to be done.

[JonasToth]

• address review comments
• rebase to master

[JonasToth]

unittests/clang-tidy/AddConstTest.cpp

15 ↗

(On Diff #182345)

Wups, relict of older version.

[JonasToth]

ping :)

[lebedev.ri]

I think this looks good now, one nit about test coverage.
Did you run this through your buildbot, any issues?

clang-tidy/utils/FixItHintUtils.cpp

35 ↗

(On Diff #175444)

There is a test for that, right?

unittests/clang-tidy/AddConstTest.cpp

733 ↗

(On Diff #173569)

How about https://en.cppreference.com/w/cpp/language/function_template#Explicit_instantiation ?
I don't see any tests for that.

[lebedev.ri]

unittests/clang-tidy/AddConstTest.cpp

733 ↗

(On Diff #173569)

Also, is there any test coverage missing for
https://en.cppreference.com/w/cpp/language/template_specialization
and
https://en.cppreference.com/w/cpp/language/partial_specialization
?

[JonasToth]

clang-tidy/utils/FixItHintUtils.cpp

35 ↗

(On Diff #175444)

Yes, both typedef and using.

unittests/clang-tidy/AddConstTest.cpp

733 ↗

(On Diff #173569)

i added tests for specializations.

[JonasToth]

• [Misc] port patch to monorepo
• add more test cases for the transformation

[JonasToth]

I know it has been a long time, but this patch is ready, i think :)
i would appreciate some reviews ;)

[aaron.ballman]

clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp

31–32

ObjC pointer types?

35–42

I don't see how these are improvements over checking QT->isArrayType() and friends within the caller.

83

Do you need both casts for Twine? I would imagine only the first is needed.

151

I think this path is reachable -- it should be an assert() instead and return None.

177

I think Context should be by reference instead of by pointer.

213–214

I think this is reachable as well.

clang-tools-extra/clang-tidy/utils/FixItHintUtils.h

27

const -> qualifier (similar for the comments in the enumerators)

33

Same here.

37

goes for -> attaches to?

45

Comment seems out of date here as well.

[JonasToth]

• create fresh branch with latest diff of the revision
• fix review comments

clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp

35–42

True!

83

In case of ' ' it is necessary, in case of " " its not. I go with " ", should not be more expensive or anything, right?

151

When testing LLVM i saw some path triggering the assertions and unreachables.

I want to go the None-route for now and only emit warnings without fixit. That will help to find false-positives unhandled cases better and is less problematic.

Is it only objc-code that could trigger this?

[JonasToth]

• fix brace

[JonasToth]

• improve test situation and fix a crash coming from invalid source locations

[JonasToth]

• adjust skipLParens code slightly to remove redundant checks

[JonasToth]

• clarify FIXME problem

[aaron.ballman]

I think this generally looks good, thank you for all the hard work on this! I just found some minor nits and testing requests. Assuming no surprises with the tests, LGTM.

clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp

175–176

Unrelated change?

clang-tools-extra/clang-tidy/utils/FixItHintUtils.h

37

attaches for -> attaches to

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

66

I don't think this is needed -- just add a newline between the literals and let string concat work its magic? (Same elsewhere)

StringRef S = "typedef int MyInt;"
              "MyInt target = 0;";

83–84

This does what I would expect, but boy does it make me sad to see (because target is not actually a const int * but is instead an int * const).

535

Can you add a test for this scenario:

struct S {
  int i;
} x = { 0 };

where you want to apply the const to the type of x?

1006

Can you also add some ObjC pointer tests?

[JonasToth]

• address review comments

[JonasToth]

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

66

My Idea was to highlight the expected code-change and create both the before and after-version from the same snippets.
With S being all the code, i would need to test for the full code.

I think with your proposal the test looks like this:

StringRef S = "typedef int MyInt;"
              "MyInt target = 0;";
EXPECT_EQ("typedef int MyInt;"
          "const MyInt target = 0;",
          runCheckOnCode<ValueLTransform>(S));

I prefer the current version, especially with the bigger test later this file.

83–84

You are right, but I am not sure what the proper policy should be. I think the smarts to detect such potential improper const should be in the library code calling the transformation.
The utility should allow both transformations.

1006

i added the most basic test, do you think more is necessary? I don't know a lot about the objc languages.

[aaron.ballman]

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

66

Okay, that's a good point. Also, this is testing code, so if it's a bit... odd... it's not an issue.

83–84

I think the API behaves how I would expect it to and agree that the caller should be the one deciding what to add the qualifier to. It just hurts me to see the test code verifying it (but the test code is good). ;-)

1006

Ah, those are regular C pointers, not ObjC pointers. I was thinking more along the lines of:

@class Object;
Object *g; // Try adding const to this

@interface Inter
- (void) foo1: (int *)arg1; // Try adding const to this parameter
@end

[JonasToth]

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

1006

Well, those don't work well.
Can i still commit? :) FIXMEs are there.

[JonasToth]

• add proper objc test, that fail mostly

[aaron.ballman]

Still LG with a small nit in one of the FIXME tests.

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

1006

Can i still commit? :) FIXMEs are there.

Yes, I think you've still made good progress with the patch as-is. We can correct the ObjC stuff in a follow-up.

1056

The whitespace looks incorrect here.

[JonasToth]

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

1056

It does, but it is actually how it is expected to look.
All pointer transformations create a double-blank if there was a blank before the star. My thought was, that clang-format should be used anyway, so it should do this cleanup. (especially with the -format option for clang-tidy).
The additional whitespace needs to be inserted to avoid intconst* target; for int* target; variables. Thats why it is always added, if necessary or not.

[aaron.ballman]

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

1056

It does, but it is actually how it is expected to look.

Okay, that's fair -- we usually let clang-format handle that sort of thing anyway and I cannot think of a case where the transformation would be incorrect.

[JonasToth]

Thank you for all the review over the time this took to land! :)

[thakis]

This breaks tests on Windows: http://45.33.8.238/win/5061/step_8.txt

Please take a look, and if takes a while to investigate, please revert in the meantime. (Probably needs the fno-delayed-template-instantiation kludge that's in many other tests.)

[JonasToth]

In D54395#1803552, @thakis wrote:

This breaks tests on Windows: http://45.33.8.238/win/5061/step_8.txt

Please take a look, and if takes a while to investigate, please revert in the meantime. (Probably needs the fno-delayed-template-instantiation kludge that's in many other tests.)

you are right. I belive it is "-fno-delayed-template-parsing" though. I added it to the default arguments runCheckOnCode for quickfix.

clang-tools-extra/clang-tidy/performance/ForRangeCopyCheck.cpp

 //===--- ForRangeCopyCheck.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 "ForRangeCopyCheck.h"
 #include "../utils/DeclRefExprUtils.h"
 #include "../utils/FixItHintUtils.h"
 #include "../utils/Matchers.h"
 #include "../utils/OptionsUtils.h"
 #include "../utils/TypeTraits.h"
 #include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
+#include "clang/Basic/Diagnostic.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace performance {
 
 ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
llvm::Optional<bool> Expensive =
       utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
   if (!Expensive || !*Expensive)
     return false;
   auto Diagnostic =
       diag(LoopVar.getLocation(),
            "the loop variable's type is not a reference type; this creates a "
            "copy in each iteration; consider making this a reference")
       << utils::fixit::changeVarDeclToReference(LoopVar, Context);
-  if (!LoopVar.getType().isConstQualified())
-    Diagnostic << utils::fixit::changeVarDeclToConst(LoopVar);
+  if (!LoopVar.getType().isConstQualified()) {
+    if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
+            LoopVar, Context, DeclSpec::TQ::TQ_const))
+      Diagnostic << *Fix;
+  }
   return true;
 }
 
 bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
     const VarDecl &LoopVar, const CXXForRangeStmt &ForRange,
     ASTContext &Context) {
   llvm::Optional<bool> Expensive =
       utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
   if (LoopVar.getType().isConstQualified() || !Expensive || !*Expensive)
     return false;
   // We omit the case where the loop variable is not used in the loop body. E.g.
   //
   // for (auto _ : benchmark_state) {
   // }
   //
   // Because the fix (changing to `const auto &`) will introduce an unused
   // compiler warning which can't be suppressed.
   // Since this case is very rare, it is safe to ignore it.
   if (!ExprMutationAnalyzer(*ForRange.getBody(), Context).isMutated(&LoopVar) &&
       !utils::decl_ref_expr::allDeclRefExprs(LoopVar, *ForRange.getBody(),
                                              Context)
            .empty()) {
-    diag(LoopVar.getLocation(),
-         "loop variable is copied but only used as const reference; consider "
-         "making it a const reference")
-        << utils::fixit::changeVarDeclToConst(LoopVar)
-        << utils::fixit::changeVarDeclToReference(LoopVar, Context);
+    auto Diag = diag(
+        LoopVar.getLocation(),
+        "making it a const reference");
+
+    if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
+            LoopVar, Context, DeclSpec::TQ::TQ_const))
+      Diag << *Fix << utils::fixit::changeVarDeclToReference(LoopVar, Context);
+
     return true;
   }
   return false;
 }
 
 } // namespace performance
 } // namespace tidy
 } // namespace clang

clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp

 //===--- UnnecessaryCopyInitialization.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 "UnnecessaryCopyInitialization.h"
 
 #include "../utils/DeclRefExprUtils.h"
 #include "../utils/FixItHintUtils.h"
 #include "../utils/Matchers.h"
 #include "../utils/OptionsUtils.h"
+#include "clang/Basic/Diagnostic.h"
 
 namespace clang {
 namespace tidy {
 namespace performance {
 namespace {
 
 void recordFixes(const VarDecl &Var, ASTContext &Context,
                  DiagnosticBuilder &Diagnostic) {
   Diagnostic << utils::fixit::changeVarDeclToReference(Var, Context);
-  if (!Var.getType().isLocalConstQualified())
-    Diagnostic << utils::fixit::changeVarDeclToConst(Var);
+  if (!Var.getType().isLocalConstQualified()) {
+    if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
+            Var, Context, DeclSpec::TQ::TQ_const))
+      Diagnostic << *Fix;
+  }
 }
 
 } // namespace
 
 using namespace ::clang::ast_matchers;
 using utils::decl_ref_expr::isOnlyUsedAsConst;
 
 UnnecessaryCopyInitialization::UnnecessaryCopyInitialization(

clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp

void UnnecessaryValueParamCheck::check(const MatchFinder::MatchResult &Result) {
   for (const auto *FunctionDecl = Function; FunctionDecl != nullptr;
        FunctionDecl = FunctionDecl->getPreviousDecl()) {
     const auto &CurrentParam = *FunctionDecl->getParamDecl(Index);
     Diag << utils::fixit::changeVarDeclToReference(CurrentParam,
                                                    *Result.Context);
     // The parameter of each declaration needs to be checked individually as to
     // whether it is const or not as constness can differ between definition and
     // declaration.
-    if (!CurrentParam.getType().getCanonicalType().isConstQualified())
-      Diag << utils::fixit::changeVarDeclToConst(CurrentParam);
+    if (!CurrentParam.getType().getCanonicalType().isConstQualified()) {
+      if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl(
+              CurrentParam, *Result.Context, DeclSpec::TQ::TQ_const))
+        Diag << *Fix;
+    }
   }
 }
 
 void UnnecessaryValueParamCheck::registerPPCallbacks(
     const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
-  Inserter = std::make_unique<utils::IncludeInserter>(SM, getLangOpts(),
-                                                       IncludeStyle);
+  Inserter =
+      std::make_unique<utils::IncludeInserter>(SM, getLangOpts(), IncludeStyle);
   PP->addPPCallbacks(Inserter->CreatePPCallbacks());
 }
 
 void UnnecessaryValueParamCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "IncludeStyle",
                 utils::IncludeSorter::toString(IncludeStyle));
   Options.store(Opts, "AllowedTypes",

clang-tools-extra/clang-tidy/utils/FixItHintUtils.h

 //===--- FixItHintUtils.h - clang-tidy---------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_FIXITHINTUTILS_H
 #define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_FIXITHINTUTILS_H
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
+#include "clang/Sema/DeclSpec.h"
 
 namespace clang {
 namespace tidy {
 namespace utils {
 namespace fixit {
 
 /// Creates fix to make ``VarDecl`` a reference by adding ``&``.
 FixItHint changeVarDeclToReference(const VarDecl &Var, ASTContext &Context);
 
 /// Creates fix to make ``VarDecl`` const qualified.
 FixItHint changeVarDeclToConst(const VarDecl &Var);
 
+/// This enum defines where the qualifier shall be preferably added.
+enum class QualifierPolicy {
+  Left,  // Add the qualifier always to the left side, if that is possible.
+  Right, // Add the qualifier always to the right side.
+};
+
+/// This enum defines which entity is the target for adding the qualifier. This
+/// makes only a difference for pointer-types. Other types behave identical
+/// for either value of \c ConstTarget.
+enum class QualifierTarget {
+  Pointee, /// Transforming a pointer attaches for the pointee and not the
+           /// pointer itself. For references and normal values this option has
+           /// no effect. `int * p = &i;` -> `const int * p = &i` or `int const
+           /// * p = &i`.
+  Value,   /// Transforming pointers will consider the pointer itself.
+           /// `int * p = &i;` -> `int * const = &i`
+};
+
+/// \brief Creates fix to qualify ``VarDecl`` with the specified \c Qualifier.
+/// Requires that `Var` is isolated in written code like in `int foo = 42;`.
+Optional<FixItHint>
+addQualifierToVarDecl(const VarDecl &Var, const ASTContext &Context,
+                      DeclSpec::TQ Qualifier,
+                      QualifierTarget CT = QualifierTarget::Pointee,
+                      QualifierPolicy CP = QualifierPolicy::Left);
 } // namespace fixit
 } // namespace utils
 } // namespace tidy
 } // namespace clang
 
 #endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_UTILS_FIXITHINTUTILS_H

clang-tools-extra/clang-tidy/utils/FixItHintUtils.cpp

 //===--- FixItHintUtils.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 "FixItHintUtils.h"
 #include "LexerUtils.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Type.h"
 
 namespace clang {
 namespace tidy {
 namespace utils {
 namespace fixit {
 
 FixItHint changeVarDeclToReference(const VarDecl &Var, ASTContext &Context) {
   SourceLocation AmpLocation = Var.getLocation();
   auto Token = utils::lexer::getPreviousToken(
       AmpLocation, Context.getSourceManager(), Context.getLangOpts());
   if (!Token.is(tok::unknown))
     AmpLocation = Lexer::getLocForEndOfToken(Token.getLocation(), 0,
                                              Context.getSourceManager(),
                                              Context.getLangOpts());
   return FixItHint::CreateInsertion(AmpLocation, "&");
 }
 
-FixItHint changeVarDeclToConst(const VarDecl &Var) {
-  return FixItHint::CreateInsertion(Var.getTypeSpecStartLoc(), "const ");
+static bool isValueType(const Type *T) {
+  return !(isa<PointerType>(T) || isa<ReferenceType>(T) || isa<ArrayType>(T) ||
+           isa<MemberPointerType>(T) || isa<ObjCObjectPointerType>(T));
 }
+static bool isValueType(QualType QT) { return isValueType(QT.getTypePtr()); }
+static bool isMemberOrFunctionPointer(QualType QT) {
+  return (QT->isPointerType() && QT->isFunctionPointerType()) ||
+         isa<MemberPointerType>(QT.getTypePtr());
+}
+
+static bool locDangerous(SourceLocation S) {
+  return S.isInvalid() || S.isMacroID();
+}
+
+static Optional<SourceLocation>
+skipLParensBackwards(SourceLocation Start, const ASTContext &Context) {
+  if (locDangerous(Start))
+    return None;
+
+  auto PreviousTokenLParen = [&Start, &Context]() {
+    Token T;
+    T = lexer::getPreviousToken(Start, Context.getSourceManager(),
+                                Context.getLangOpts());
+    return T.is(tok::l_paren);
+  };
+
+  while (Start.isValid() && PreviousTokenLParen())
+    Start = lexer::findPreviousTokenStart(Start, Context.getSourceManager(),
+                                          Context.getLangOpts());
+
+  if (locDangerous(Start))
+    return None;
+  return Start;
+}
+
+static Optional<FixItHint> fixIfNotDangerous(SourceLocation Loc,
+                                             StringRef Text) {
+  if (locDangerous(Loc))
+    return None;
+  return FixItHint::CreateInsertion(Loc, Text);
+}
+
+// Build a string that can be emitted as FixIt with either a space in before
+// or after the qualifier, either ' const' or 'const '.
+static std::string buildQualifier(DeclSpec::TQ Qualifier,
+                                  bool WhitespaceBefore = false) {
+  if (WhitespaceBefore)
+    return (llvm::Twine(' ') + DeclSpec::getSpecifierName(Qualifier)).str();
+  return (llvm::Twine(DeclSpec::getSpecifierName(Qualifier)) + " ").str();
+}
+
+static Optional<FixItHint> changeValue(const VarDecl &Var,
+                                       DeclSpec::TQ Qualifier,
+                                       QualifierTarget QualTarget,
+                                       QualifierPolicy QualPolicy,
+                                       const ASTContext &Context) {
+  switch (QualPolicy) {
+  case QualifierPolicy::Left:
+    return fixIfNotDangerous(Var.getTypeSpecStartLoc(),
+                             buildQualifier(Qualifier));
+  case QualifierPolicy::Right:
+    Optional<SourceLocation> IgnoredParens =
+        skipLParensBackwards(Var.getLocation(), Context);
+
+    if (IgnoredParens)
+      return fixIfNotDangerous(*IgnoredParens, buildQualifier(Qualifier));
+    return None;
+  }
+}
+
+static Optional<FixItHint> changePointerItself(const VarDecl &Var,
+                                               DeclSpec::TQ Qualifier,
+                                               const ASTContext &Context) {
+  if (locDangerous(Var.getLocation()))
+    return None;
+
+  Optional<SourceLocation> IgnoredParens =
+      skipLParensBackwards(Var.getLocation(), Context);
+  if (IgnoredParens)
+    return fixIfNotDangerous(*IgnoredParens, buildQualifier(Qualifier));
+  return None;
+}
+
+static Optional<FixItHint>
+changePointer(const VarDecl &Var, DeclSpec::TQ Qualifier, const Type *Pointee,
+              QualifierTarget QualTarget, QualifierPolicy QualPolicy,
+              const ASTContext &Context) {
+  // The pointer itself shall be marked as `const`. This is always to the right
+  // of the '*' or in front of the identifier.
+  if (QualTarget == QualifierTarget::Value)
+    return changePointerItself(Var, Qualifier, Context);
+
+  // Mark the pointee `const` that is a normal value (`int* p = nullptr;`).
+  if (QualTarget == QualifierTarget::Pointee && isValueType(Pointee)) {
+    // Adding the `const` on the left side is just the beginning of the type
+    // specification. (`const int* p = nullptr;`)
+    if (QualPolicy == QualifierPolicy::Left)
+      return fixIfNotDangerous(Var.getTypeSpecStartLoc(),
+                               buildQualifier(Qualifier));
 
+    // Adding the `const` on the right side of the value type requires finding
+    // the `*` token and placing the `const` left of it.
+    // (`int const* p = nullptr;`)
+    if (QualPolicy == QualifierPolicy::Right) {
+      SourceLocation BeforeStar = lexer::findPreviousTokenKind(
+          Var.getLocation(), Context.getSourceManager(), Context.getLangOpts(),
+          tok::star);
+      if (locDangerous(BeforeStar))
+        return None;
+
+      Optional<SourceLocation> IgnoredParens =
+          skipLParensBackwards(BeforeStar, Context);
+
+      if (IgnoredParens)
+        return fixIfNotDangerous(*IgnoredParens,
+                                 buildQualifier(Qualifier, true));
+      return None;
+    }
+  }
+
+  if (QualTarget == QualifierTarget::Pointee && Pointee->isPointerType()) {
+    // Adding the `const` to the pointee if the pointee is a pointer
+    // is the same as 'QualPolicy == Right && isValueType(Pointee)'.
+    // The `const` must be left of the last `*` token.
+    // (`int * const* p = nullptr;`)
+    SourceLocation BeforeStar = lexer::findPreviousTokenKind(
+        Var.getLocation(), Context.getSourceManager(), Context.getLangOpts(),
+        tok::star);
+    return fixIfNotDangerous(BeforeStar, buildQualifier(Qualifier, true));
+  }
+
+  return None;
+}
+
+static Optional<FixItHint>
+changeReferencee(const VarDecl &Var, DeclSpec::TQ Qualifier, QualType Pointee,
+                 QualifierTarget QualTarget, QualifierPolicy QualPolicy,
+                 const ASTContext &Context) {
+  if (QualPolicy == QualifierPolicy::Left && isValueType(Pointee))
+    return fixIfNotDangerous(Var.getTypeSpecStartLoc(),
+                             buildQualifier(Qualifier));
+
+  SourceLocation BeforeRef = lexer::findPreviousAnyTokenKind(
+      Var.getLocation(), Context.getSourceManager(), Context.getLangOpts(),
+      tok::amp, tok::ampamp);
+  Optional<SourceLocation> IgnoredParens =
+      skipLParensBackwards(BeforeRef, Context);
+  if (IgnoredParens)
+    return fixIfNotDangerous(*IgnoredParens, buildQualifier(Qualifier, true));
+
+  return None;
+}
+
+Optional<FixItHint> addQualifierToVarDecl(const VarDecl &Var,
+                                          const ASTContext &Context,
+                                          DeclSpec::TQ Qualifier,
+                                          QualifierTarget QualTarget,
+                                          QualifierPolicy QualPolicy) {
+  assert((QualPolicy == QualifierPolicy::Left ||
+          QualPolicy == QualifierPolicy::Right) &&
+         "Unexpected Insertion Policy");
+  assert((QualTarget == QualifierTarget::Pointee ||
+          QualTarget == QualifierTarget::Value) &&
+         "Unexpected Target");
+
+  QualType ParenStrippedType = Var.getType().IgnoreParens();
+  if (isValueType(ParenStrippedType))
+    return changeValue(Var, Qualifier, QualTarget, QualPolicy, Context);
+
+  if (ParenStrippedType->isReferenceType())
+    return changeReferencee(Var, Qualifier, Var.getType()->getPointeeType(),
+                            QualTarget, QualPolicy, Context);
+
+  if (isMemberOrFunctionPointer(ParenStrippedType))
+    return changePointerItself(Var, Qualifier, Context);
+
+  if (ParenStrippedType->isPointerType())
+    return changePointer(Var, Qualifier,
+                         ParenStrippedType->getPointeeType().getTypePtr(),
+                         QualTarget, QualPolicy, Context);
+
+  if (ParenStrippedType->isArrayType()) {
+    const Type *AT = ParenStrippedType->getBaseElementTypeUnsafe();
+    assert(AT && "Did not retrieve array element type for an array.");
+
+    if (isValueType(AT))
+      return changeValue(Var, Qualifier, QualTarget, QualPolicy, Context);
+
+    if (AT->isPointerType())
+      return changePointer(Var, Qualifier, AT->getPointeeType().getTypePtr(),
+                           QualTarget, QualPolicy, Context);
+  }
+
+  return None;
+}
 } // namespace fixit
 } // namespace utils
 } // namespace tidy
 } // namespace clang

clang-tools-extra/clang-tidy/utils/LexerUtils.h

 SourceLocation findNextTerminator(SourceLocation Start, const SourceManager &SM,
                                   const LangOptions &LangOpts);
 
 template <typename TokenKind, typename... TokenKinds>
 SourceLocation findPreviousAnyTokenKind(SourceLocation Start,
                                         const SourceManager &SM,
                                         const LangOptions &LangOpts,
                                         TokenKind TK, TokenKinds... TKs) {
+  if (Start.isInvalid() || Start.isMacroID())
+    return SourceLocation();
   while (true) {
     SourceLocation L = findPreviousTokenStart(Start, SM, LangOpts);
     if (L.isInvalid() || L.isMacroID())
       return SourceLocation();
 
     Token T;
     // Returning 'true' is used to signal failure to retrieve the token.
-    if (Lexer::getRawToken(L, T, SM, LangOpts))
+    if (Lexer::getRawToken(L, T, SM, LangOpts, /*IgnoreWhiteSpace=*/true))
       return SourceLocation();
 
     if (T.isOneOf(TK, TKs...))
       return T.getLocation();
 
     Start = L;
   }
 }

clang-tools-extra/clang-tidy/utils/LexerUtils.cpp

 namespace tidy {
 namespace utils {
 namespace lexer {
 
 Token getPreviousToken(SourceLocation Location, const SourceManager &SM,
                        const LangOptions &LangOpts, bool SkipComments) {
   Token Token;
   Token.setKind(tok::unknown);
+
   Location = Location.getLocWithOffset(-1);
+  if (Location.isInvalid())
+      return Token;
+
   auto StartOfFile = SM.getLocForStartOfFile(SM.getFileID(Location));
   while (Location != StartOfFile) {
     Location = Lexer::GetBeginningOfToken(Location, SM, LangOpts);
     if (!Lexer::getRawToken(Location, Token, SM, LangOpts) &&
         (!SkipComments || !Token.is(tok::comment))) {
       break;
     }
     Location = Location.getLocWithOffset(-1);
SourceLocation findPreviousTokenStart(SourceLocation Start,
 
   return Lexer::GetBeginningOfToken(BeforeStart, SM, LangOpts);
 }
 
 SourceLocation findPreviousTokenKind(SourceLocation Start,
                                      const SourceManager &SM,
                                      const LangOptions &LangOpts,
                                      tok::TokenKind TK) {
+  if (Start.isInvalid() || Start.isMacroID())
+    return SourceLocation();
+
   while (true) {
     SourceLocation L = findPreviousTokenStart(Start, SM, LangOpts);
     if (L.isInvalid() || L.isMacroID())
       return SourceLocation();
 
     Token T;
     if (Lexer::getRawToken(L, T, SM, LangOpts, /*IgnoreWhiteSpace=*/true))
       return SourceLocation();

clang-tools-extra/unittests/clang-tidy/AddConstTest.cpp

+#include "../clang-tidy/utils/FixItHintUtils.h"
+#include "ClangTidyTest.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Tooling/Tooling.h"
+#include "gtest/gtest.h"
+
+namespace clang {
+namespace tidy {
+
+namespace {
+using namespace clang::ast_matchers;
+using namespace utils::fixit;
+
+template <QualifierTarget CT, QualifierPolicy CP>
+class ConstTransform : public ClangTidyCheck {
+public:
+  ConstTransform(StringRef CheckName, ClangTidyContext *Context)
+      : ClangTidyCheck(CheckName, Context) {}
+
+  void registerMatchers(MatchFinder *Finder) override {
+    Finder->addMatcher(varDecl(hasName("target")).bind("var"), this);
+  }
+
+  void check(const MatchFinder::MatchResult &Result) override {
+    const auto *D = Result.Nodes.getNodeAs<VarDecl>("var");
+    using utils::fixit::addQualifierToVarDecl;
+    Optional<FixItHint> Fix = addQualifierToVarDecl(
+        *D, *Result.Context, DeclSpec::TQ::TQ_const, CT, CP);
+    auto Diag = diag(D->getBeginLoc(), "doing const transformation");
+    if (Fix)
+      Diag << *Fix;
+  }
+};
+} // namespace
+
+namespace test {
+using PointeeLTransform =
+    ConstTransform<QualifierTarget::Pointee, QualifierPolicy::Left>;
+using PointeeRTransform =
+    ConstTransform<QualifierTarget::Pointee, QualifierPolicy::Right>;
+
+using ValueLTransform =
+    ConstTransform<QualifierTarget::Value, QualifierPolicy::Left>;
+using ValueRTransform =
+    ConstTransform<QualifierTarget::Value, QualifierPolicy::Right>;
+
+// ----------------------------------------------------------------------------
+// Test Value-like types. Everything with indirection is done later.
+// ----------------------------------------------------------------------------
+
+TEST(Values, Builtin) {
+  StringRef Snippet = "int target = 0;";
+
+  EXPECT_EQ("const int target = 0;", runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("const int target = 0;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int const target = 0;", runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int const target = 0;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Values, TypedefBuiltin) {
+  StringRef T = "typedef int MyInt;";
+  StringRef S = "MyInt target = 0;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const MyInt target = 0;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const MyInt target = 0;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("MyInt const target = 0;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("MyInt const target = 0;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, TypedefBuiltinPointer) {
+  StringRef T = "typedef int* MyInt;";
+  StringRef S = "MyInt target = nullptr;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const MyInt target = nullptr;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const MyInt target = nullptr;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("MyInt const target = nullptr;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("MyInt const target = nullptr;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, UsingBuiltin) {
+  StringRef T = "using MyInt = int;";
+  StringRef S = "MyInt target = 0;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const MyInt target = 0;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const MyInt target = 0;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("MyInt const target = 0;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("MyInt const target = 0;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, UsingBuiltinPointer) {
+  StringRef T = "using MyInt = int*;";
+  StringRef S = "MyInt target = nullptr;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const MyInt target = nullptr;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const MyInt target = nullptr;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("MyInt const target = nullptr;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("MyInt const target = nullptr;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, AutoValue) {
+  StringRef T = "int f() { return 42; }\n";
+  StringRef S = "auto target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, AutoPointer) {
+  StringRef T = "int* f() { return nullptr; }\n";
+  StringRef S = "auto target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, AutoReference) {
+  StringRef T = "static int global = 42; int& f() { return global; }\n";
+  StringRef S = "auto target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const auto target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, DeclTypeValue) {
+  StringRef T = "int f() { return 42; }\n";
+  StringRef S = "decltype(f()) target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, DeclTypePointer) {
+  // The pointer itself will be changed to 'const'. There is no
+  // way to make the pointee 'const' with this syntax.
+  StringRef T = "int* f() { return nullptr; }\n";
+  StringRef S = "decltype(f()) target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, DeclTypeReference) {
+  // Same as pointer, but the reference itself will be marked 'const'.
+  // This has no effect and will result in a warning afterwards. The
+  // transformation itself is still correct.
+  StringRef T = "static int global = 42; int& f() { return global; }\n";
+  StringRef S = "decltype(f()) target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const decltype(f()) target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("decltype(f()) const target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Values, Parens) {
+  StringRef Snippet = "int ((target)) = 0;";
+
+  EXPECT_EQ("const int ((target)) = 0;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("const int ((target)) = 0;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int const ((target)) = 0;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int const ((target)) = 0;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+
+// ----------------------------------------------------------------------------
+// Test builtin-arrays
+// ----------------------------------------------------------------------------
+
+TEST(Arrays, Builtin) {
+  StringRef Snippet = "int target[][1] = {{1}, {2}, {3}};";
+
+  EXPECT_EQ("const int target[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("const int target[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<ValueLTransform>(Snippet));
+
+  EXPECT_EQ("int const target[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+  EXPECT_EQ("int const target[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<ValueRTransform>(Snippet));
+}
+TEST(Arrays, BuiltinParens) {
+  StringRef Snippet = "int ((target))[][1] = {{1}, {2}, {3}};";
+
+  EXPECT_EQ("const int ((target))[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("const int ((target))[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<ValueLTransform>(Snippet));
+
+  EXPECT_EQ("int const ((target))[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+  EXPECT_EQ("int const ((target))[][1] = {{1}, {2}, {3}};",
+            runCheckOnCode<ValueRTransform>(Snippet));
+}
+TEST(Arrays, Pointers) {
+  StringRef Snippet = "int x; int* target[] = {&x, &x, &x};";
+
+  EXPECT_EQ("int x; const int* target[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int x; int const* target[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+
+  EXPECT_EQ("int x; int* const target[] = {&x, &x, &x};",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int x; int* const target[] = {&x, &x, &x};",
+            runCheckOnCode<ValueRTransform>(Snippet));
+}
+TEST(Arrays, PointerPointers) {
+  StringRef Snippet = "int* x = nullptr; int** target[] = {&x, &x, &x};";
+
+  EXPECT_EQ("int* x = nullptr; int* const* target[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int* x = nullptr; int** const target[] = {&x, &x, &x};",
+            runCheckOnCode<ValueLTransform>(Snippet));
+
+  EXPECT_EQ("int* x = nullptr; int* const* target[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+  EXPECT_EQ("int* x = nullptr; int** const target[] = {&x, &x, &x};",
+            runCheckOnCode<ValueRTransform>(Snippet));
+}
+TEST(Arrays, PointersParens) {
+  StringRef Snippet = "int x; int* (target)[] = {&x, &x, &x};";
+
+  EXPECT_EQ("int x; const int* (target)[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int x; int const* (target)[] = {&x, &x, &x};",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+
+  EXPECT_EQ("int x; int* const (target)[] = {&x, &x, &x};",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int x; int* const (target)[] = {&x, &x, &x};",
+            runCheckOnCode<ValueRTransform>(Snippet));
+}
+
+// ----------------------------------------------------------------------------
+// Test reference types. This does not include pointers and arrays.
+// ----------------------------------------------------------------------------
+
+TEST(Reference, LValueBuiltin) {
+  StringRef Snippet = "int x = 42; int& target = x;";
+
+  EXPECT_EQ("int x = 42; const int& target = x;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int x = 42; const int& target = x;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int x = 42; int const& target = x;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int x = 42; int const& target = x;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Reference, RValueBuiltin) {
+  StringRef Snippet = "int&& target = 42;";
+  EXPECT_EQ("const int&& target = 42;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("const int&& target = 42;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int const&& target = 42;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int const&& target = 42;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Reference, LValueToPointer) {
+  StringRef Snippet = "int* p; int *& target = p;";
+  EXPECT_EQ("int* p; int * const& target = p;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int* p; int * const& target = p;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int* p; int * const& target = p;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int* p; int * const& target = p;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Reference, LValueParens) {
+  StringRef Snippet = "int x = 42; int ((& target)) = x;";
+
+  EXPECT_EQ("int x = 42; const int ((& target)) = x;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int x = 42; const int ((& target)) = x;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+
+  EXPECT_EQ("int x = 42; int  const((& target)) = x;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+  EXPECT_EQ("int x = 42; int  const((& target)) = x;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Reference, ToArray) {
+  StringRef ArraySnippet = "int a[4] = {1, 2, 3, 4};";
+  StringRef Snippet = "int (&target)[4] = a;";
+  auto Cat = [&ArraySnippet](StringRef S) { return (ArraySnippet + S).str(); };
+
+  EXPECT_EQ(Cat("const int (&target)[4] = a;"),
+            runCheckOnCode<ValueLTransform>(Cat(Snippet)));
+  EXPECT_EQ(Cat("const int (&target)[4] = a;"),
+            runCheckOnCode<PointeeLTransform>(Cat(Snippet)));
+
+  EXPECT_EQ(Cat("int  const(&target)[4] = a;"),
+            runCheckOnCode<ValueRTransform>(Cat(Snippet)));
+  EXPECT_EQ(Cat("int  const(&target)[4] = a;"),
+            runCheckOnCode<PointeeRTransform>(Cat(Snippet)));
+}
+TEST(Reference, Auto) {
+  StringRef T = "static int global = 42; int& f() { return global; }\n";
+  StringRef S = "auto& target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const auto& target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const& target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("const auto& target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const& target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+
+// ----------------------------------------------------------------------------
+// Test pointers types.
+// ----------------------------------------------------------------------------
+
+TEST(Pointers, SingleBuiltin) {
+  StringRef Snippet = "int* target = nullptr;";
+
+  EXPECT_EQ("int* const target = nullptr;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int* const target = nullptr;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+
+  EXPECT_EQ("const int* target = nullptr;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int const* target = nullptr;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Pointers, MultiBuiltin) {
+  StringRef Snippet = "int** target = nullptr;";
+
+  EXPECT_EQ("int** const target = nullptr;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int** const target = nullptr;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+
+  EXPECT_EQ("int* const* target = nullptr;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int* const* target = nullptr;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Pointers, ToArray) {
+  StringRef ArraySnippet = "int a[4] = {1, 2, 3, 4};";
+  StringRef Snippet = "int (*target)[4] = &a;";
+  auto Cat = [&ArraySnippet](StringRef S) { return (ArraySnippet + S).str(); };
+
+  EXPECT_EQ(Cat("int (*const target)[4] = &a;"),
+            runCheckOnCode<ValueLTransform>(Cat(Snippet)));
+  EXPECT_EQ(Cat("const int (*target)[4] = &a;"),
+            runCheckOnCode<PointeeLTransform>(Cat(Snippet)));
+
+  EXPECT_EQ(Cat("int (*const target)[4] = &a;"),
+            runCheckOnCode<ValueRTransform>(Cat(Snippet)));
+  EXPECT_EQ(Cat("int  const(*target)[4] = &a;"),
+            runCheckOnCode<PointeeRTransform>(Cat(Snippet)));
+}
+TEST(Pointers, Parens) {
+  StringRef Snippet = "int ((**target)) = nullptr;";
+
+  EXPECT_EQ("int ((**const target)) = nullptr;",
+            runCheckOnCode<ValueLTransform>(Snippet));
+  EXPECT_EQ("int ((**const target)) = nullptr;",
+            runCheckOnCode<ValueRTransform>(Snippet));
+
+  EXPECT_EQ("int ((* const*target)) = nullptr;",
+            runCheckOnCode<PointeeLTransform>(Snippet));
+  EXPECT_EQ("int ((* const*target)) = nullptr;",
+            runCheckOnCode<PointeeRTransform>(Snippet));
+}
+TEST(Pointers, Auto) {
+  StringRef T = "int* f() { return nullptr; }\n";
+  StringRef S = "auto* target = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("auto* const target = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto* const target = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("const auto* target = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto const* target = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Pointers, AutoParens) {
+  StringRef T = "int* f() { return nullptr; }\n";
+  StringRef S = "auto (((* target))) = f();";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("auto (((* const target))) = f();"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto (((* const target))) = f();"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("const auto (((* target))) = f();"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("auto  const(((* target))) = f();"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Pointers, FunctionPointer) {
+  StringRef S = "int (*target)(float, int, double) = nullptr;";
+
+  EXPECT_EQ("int (*const target)(float, int, double) = nullptr;",
+            runCheckOnCode<ValueLTransform>(S));
+  EXPECT_EQ("int (*const target)(float, int, double) = nullptr;",
+            runCheckOnCode<ValueRTransform>(S));
+
+  EXPECT_EQ("int (*const target)(float, int, double) = nullptr;",
+            runCheckOnCode<PointeeLTransform>(S));
+  EXPECT_EQ("int (*const target)(float, int, double) = nullptr;",
+            runCheckOnCode<PointeeRTransform>(S));
+
+  S = "int (((*target)))(float, int, double) = nullptr;";
+  EXPECT_EQ("int (((*const target)))(float, int, double) = nullptr;",
+            runCheckOnCode<PointeeRTransform>(S));
+}
+TEST(Pointers, MemberFunctionPointer) {
+  StringRef T = "struct A { int f() { return 1; } };";
+  StringRef S = "int (A::*target)() = &A::f;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("int (A::*const target)() = &A::f;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("int (A::*const target)() = &A::f;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("int (A::*const target)() = &A::f;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("int (A::*const target)() = &A::f;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "int (A::*((target)))() = &A::f;";
+  EXPECT_EQ(Cat("int (A::*const ((target)))() = &A::f;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+}
+TEST(Pointers, MemberDataPointer) {
+  StringRef T = "struct A { int member = 0; };";
+  StringRef S = "int A::*target = &A::member;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("int A::*const target = &A::member;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("int A::*const target = &A::member;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("int A::*const target = &A::member;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("int A::*const target = &A::member;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "int A::*((target)) = &A::member;";
+  EXPECT_EQ(Cat("int A::*const ((target)) = &A::member;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+
+// ----------------------------------------------------------------------------
+// Test TagTypes (struct, class, unions, enums)
+// ----------------------------------------------------------------------------
+
+TEST(TagTypes, Struct) {
+  StringRef T = "struct Foo { int data; int method(); };\n";
+  StringRef S = "struct Foo target{0};";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const struct Foo target{0};"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const struct Foo target{0};"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("struct Foo const target{0};"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("struct Foo const target{0};"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo target{0};";
+  EXPECT_EQ(Cat("const Foo target{0};"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo target{0};"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const target{0};"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const target{0};"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo (target){0};";
+  EXPECT_EQ(Cat("const Foo (target){0};"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo (target){0};"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const (target){0};"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const (target){0};"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(TagTypes, Class) {
+  StringRef T = "class Foo { int data; int method(); };\n";
+  StringRef S = "class Foo target;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const class Foo target;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const class Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("class Foo const target;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("class Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo target;";
+  EXPECT_EQ(Cat("const Foo target;"), runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const target;"), runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo (target);";
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(TagTypes, Enum) {
+  StringRef T = "enum Foo { N_ONE, N_TWO, N_THREE };\n";
+  StringRef S = "enum Foo target;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const enum Foo target;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const enum Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("enum Foo const target;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("enum Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo target;";
+  EXPECT_EQ(Cat("const Foo target;"), runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const target;"), runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo (target);";
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(TagTypes, Union) {
+  StringRef T = "union Foo { int yay; float nej; };\n";
+  StringRef S = "union Foo target;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("const union Foo target;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const union Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("union Foo const target;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("union Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo target;";
+  EXPECT_EQ(Cat("const Foo target;"), runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo target;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const target;"), runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const target;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+
+  S = "Foo (target);";
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("const Foo (target);"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("Foo const (target);"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+
+// ----------------------------------------------------------------------------
+// Test Macro expansions.
+// ----------------------------------------------------------------------------
+
+TEST(Macro, AllInMacro) {
+  StringRef T = "#define DEFINE_VARIABLE int target = 42\n";
+  StringRef S = "DEFINE_VARIABLE;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("DEFINE_VARIABLE;"), runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("DEFINE_VARIABLE;"), runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("DEFINE_VARIABLE;"), runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("DEFINE_VARIABLE;"), runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Macro, MacroParameter) {
+  StringRef T = "#define DEFINE_VARIABLE(X) int X = 42\n";
+  StringRef S = "DEFINE_VARIABLE(target);";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("DEFINE_VARIABLE(target);"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("DEFINE_VARIABLE(target);"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("DEFINE_VARIABLE(target);"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("DEFINE_VARIABLE(target);"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Macro, MacroTypeValue) {
+  StringRef T = "#define BAD_TYPEDEF int\n";
+  StringRef S = "BAD_TYPEDEF target = 42;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("BAD_TYPEDEF target = 42;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("BAD_TYPEDEF target = 42;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("BAD_TYPEDEF const target = 42;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("BAD_TYPEDEF const target = 42;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+}
+TEST(Macro, MacroTypePointer) {
+  StringRef T = "#define BAD_TYPEDEF int *\n";
+  StringRef S = "BAD_TYPEDEF target = nullptr;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("BAD_TYPEDEF const target = nullptr;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("BAD_TYPEDEF const target = nullptr;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  // FIXME: Failing even all parts seem to bail-out in for isMacroID()
+  // The macro itself is changed here and below which is not intended.
+  EXPECT_NE(Cat("BAD_TYPEDEF target = nullptr;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+  EXPECT_EQ(Cat("BAD_TYPEDEF target = nullptr;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+}
+TEST(Macro, MacroTypeReference) {
+  StringRef T = "static int g = 42;\n#define BAD_TYPEDEF int&\n";
+  StringRef S = "BAD_TYPEDEF target = g;";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("BAD_TYPEDEF target = g;"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  // FIXME: Failing even all parts seem to bail-out in for isMacroID()
+  EXPECT_NE(Cat("BAD_TYPEDEF target = g;"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("BAD_TYPEDEF target = g;"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  // FIXME: Failing even all parts seem to bail-out in for isMacroID()
+  EXPECT_NE(Cat("BAD_TYPEDEF target = g;"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+// This failed in LLVM.
+TEST(Macro, Variable) {
+  StringRef M = "#define DEBUG(X) do { if (1) { X; } } while (0)\n";
+  StringRef F = "void foo() ";
+  StringRef V = "{ DEBUG(int target = 42;); }";
+
+  auto Cat = [&](StringRef S) { return (M + F + V).str(); };
+
+  EXPECT_EQ(Cat("{ DEBUG(const int target = 42;); }"),
+            runCheckOnCode<ValueLTransform>(Cat(V)));
+  EXPECT_EQ(Cat("{ DEBUG(int const target = 42;); }"),
+            runCheckOnCode<ValueRTransform>(Cat(V)));
+}
+TEST(Macro, RangeLoop) {
+  StringRef M = "#define DEBUG(X) do { if (1) { X; }} while (false)\n";
+  StringRef F = "void foo() { char array[] = {'a', 'b', 'c'}; ";
+  StringRef V = "DEBUG( for(auto& target: array) 10 + target; );";
+  StringRef E = "}";
+
+  auto Cat = [&](StringRef S) { return (M + F + V + E).str(); };
+
+  EXPECT_EQ(Cat("DEBUG( for(const auto& target: array); );"),
+            runCheckOnCode<ValueLTransform>(Cat(V)));
+  EXPECT_EQ(Cat("DEBUG( for(auto const& target: array); );"),
+            runCheckOnCode<ValueRTransform>(Cat(V)));
+}
+
+// ----------------------------------------------------------------------------
+// Test template code.
+// ----------------------------------------------------------------------------
+
+TEST(Template, TemplateVariable) {
+  StringRef T = "template <typename T> T target = 3.1415;";
+
+  EXPECT_EQ("template <typename T> const T target = 3.1415;",
+            runCheckOnCode<ValueLTransform>(T));
+  EXPECT_EQ("template <typename T> T const target = 3.1415;",
+            runCheckOnCode<ValueRTransform>(T));
+
+  EXPECT_EQ("template <typename T> const T target = 3.1415;",
+            runCheckOnCode<PointeeLTransform>(T));
+  EXPECT_EQ("template <typename T> T const target = 3.1415;",
+            runCheckOnCode<PointeeRTransform>(T));
+}
+TEST(Template, FunctionValue) {
+  StringRef T = "template <typename T> void f(T v) \n";
+  StringRef S = "{ T target = v; }";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, FunctionPointer) {
+  StringRef T = "template <typename T> void f(T* v) \n";
+  StringRef S = "{ T* target = v; }";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("{ T* const target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T* const target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T* target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const* target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, FunctionReference) {
+  StringRef T = "template <typename T> void f(T& v) \n";
+  StringRef S = "{ T& target = v; }";
+  auto Cat = [&T](StringRef S) { return (T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const T& target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const& target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T& target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const& target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, MultiInstantiationsFunction) {
+  StringRef T = "template <typename T> void f(T v) \n";
+  StringRef S = "{ T target = v; }";
+  StringRef InstantStart = "void calls() {\n";
+  StringRef InstValue = "f<int>(42);\n";
+  StringRef InstConstValue = "f<const int>(42);\n";
+  StringRef InstPointer = "f<int*>(nullptr);\n";
+  StringRef InstPointerConst = "f<int* const>(nullptr);\n";
+  StringRef InstConstPointer = "f<const int*>(nullptr);\n";
+  StringRef InstConstPointerConst = "f<const int* const>(nullptr);\n";
+  StringRef InstRef = "int i = 42;\nf<int&>(i);\n";
+  StringRef InstConstRef = "f<const int&>(i);\n";
+  StringRef InstantEnd = "}";
+  auto Cat = [&](StringRef Target) {
+    return (T + Target + InstantStart + InstValue + InstConstValue +
+            InstPointer + InstPointerConst + InstConstPointer +
+            InstConstPointerConst + InstRef + InstConstRef + InstantEnd)
+        .str();
+  };
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+
+TEST(Template, StructValue) {
+  StringRef T = "template <typename T> struct S { void f(T& v) \n";
+  StringRef S = "{ T target = v; }";
+  StringRef End = "\n};";
+  auto Cat = [&T, &End](StringRef S) { return (T + S + End).str(); };
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, StructPointer) {
+  StringRef T = "template <typename T> struct S { void f(T* v) \n";
+  StringRef S = "{ T* target = v; }";
+  StringRef End = "\n};";
+  auto Cat = [&T, &End](StringRef S) { return (T + S + End).str(); };
+
+  EXPECT_EQ(Cat("{ T* const target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T* const target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T* target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const* target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, StructReference) {
+  StringRef T = "template <typename T> struct S { void f(T& v) \n";
+  StringRef S = "{ T& target = v; }";
+  StringRef End = "\n};";
+  auto Cat = [&T, &End](StringRef S) { return (T + S + End).str(); };
+
+  EXPECT_EQ(Cat("{ const T& target = v; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const& target = v; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const T& target = v; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ T const& target = v; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, DependentReturnFunction) {
+  StringRef TS = "template <typename T> struct TS { using value_type = T; };";
+  StringRef T = "template <typename T> void foo() ";
+  StringRef S = "{ typename T::value_type target; }";
+  auto Cat = [&TS, &T](StringRef S) { return (TS + T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const typename T::value_type target; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type const target; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const typename T::value_type target; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type const target; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, DependentReturnPointerFunction) {
+  StringRef TS = "template <typename T> struct TS { using value_type = T; };";
+  StringRef T = "template <typename T> void foo() ";
+  StringRef S = "{ typename T::value_type *target; }";
+  auto Cat = [&TS, &T](StringRef S) { return (TS + T + S).str(); };
+
+  EXPECT_EQ(Cat("{ typename T::value_type *const target; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type *const target; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const typename T::value_type *target; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type  const*target; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, DependentReturnReferenceFunction) {
+  StringRef TS = "template <typename T> struct TS { using value_type = T; };";
+  StringRef T = "template <typename T> void foo(T& f) ";
+  StringRef S = "{ typename T::value_type &target = f; }";
+  auto Cat = [&TS, &T](StringRef S) { return (TS + T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const typename T::value_type &target = f; }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type  const&target = f; }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const typename T::value_type &target = f; }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ typename T::value_type  const&target = f; }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, VectorLikeType) {
+  StringRef TS = "template <typename T> struct TS { TS(const T&) {} }; ";
+  StringRef T = "void foo() ";
+  StringRef S = "{ TS<int> target(42); }";
+  auto Cat = [&TS, &T](StringRef S) { return (TS + T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const TS<int> target(42); }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ TS<int> const target(42); }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const TS<int> target(42); }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ TS<int> const target(42); }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+TEST(Template, SpecializedTemplate) {
+  StringRef TS = "template <typename T = int> struct TS { TS(const T&) {} }; ";
+  StringRef TS2 = "template <> struct TS<double> { TS(const double&) {} }; ";
+  StringRef T = "void foo() ";
+  StringRef S = "{ TS<double> target(42.42); }";
+  auto Cat = [&](StringRef S) { return (TS + TS2 + T + S).str(); };
+
+  EXPECT_EQ(Cat("{ const TS<double> target(42.42); }"),
+            runCheckOnCode<ValueLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ TS<double> const target(42.42); }"),
+            runCheckOnCode<ValueRTransform>(Cat(S)));
+
+  EXPECT_EQ(Cat("{ const TS<double> target(42.42); }"),
+            runCheckOnCode<PointeeLTransform>(Cat(S)));
+  EXPECT_EQ(Cat("{ TS<double> const target(42.42); }"),
+            runCheckOnCode<PointeeRTransform>(Cat(S)));
+}
+
+} // namespace test
+} // namespace tidy
+} // namespace clang

clang-tools-extra/unittests/clang-tidy/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   support
   )
 
 get_filename_component(CLANG_LINT_SOURCE_DIR
   ${CMAKE_CURRENT_SOURCE_DIR}/../../clang-tidy REALPATH)
 include_directories(${CLANG_LINT_SOURCE_DIR})
 
 add_extra_unittest(ClangTidyTests
+  AddConstTest.cpp
   ClangTidyDiagnosticConsumerTest.cpp
   ClangTidyOptionsTest.cpp
   IncludeInserterTest.cpp
   GlobListTest.cpp
   GoogleModuleTest.cpp
   LLVMModuleTest.cpp
   NamespaceAliaserTest.cpp
   ObjCModuleTest.cpp