[include-cleaner] Handle decls/refs to concepts.

[sammccall]

I think we're not *that* far away from landing the AST change, and changing RecursiveASTVisitor now is probably confusing and not worth the churn.
So I'd prefer to wait for now...

clang-tools-extra/include-cleaner/lib/WalkAST.cpp

249

after D155858 this can be VisitConceptReference

clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp

217

to complete the set I think you want

void foo(Bar auto x) (abbreviated template param) and Bar auto x = 1 (deduced type).

Though these may not pass yet

[usaxena95]

Rebased over AST changes.

clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp

217

For some reason, Bar auto x = 1 is still failing; investigating.

[sammccall]

clang-tools-extra/include-cleaner/lib/WalkAST.cpp

244

I don't know why we're doing this, decls in general are not considered references to themselves.

Function/Var/Enum are in some cases, because their definition should be typechecked against a forward-declaration in the header. But that doesn't apply here: you can't forward-declare a concept.

clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp

201

AFAICT these are just normal AST nodes, so should be tested in WalkASTTest which is narrower and lighter-weight.

The tests in this file run a bit more code, and none of it seems specifically relevant to concepts.

[usaxena95]

Addressed comments.

[sammccall]

LGTM

Unclear to me whether the FIXME will be addressed by an AST bug or a local change, either way continuing to look into it SG but this is fine to land as-is.

[usaxena95]

closed by ac2d2652db8de9ea2b750dd2bf1232941039dffe

clang-tools-extra/include-cleaner/lib/WalkAST.cpp

public:
   bool VisitEnumDecl(EnumDecl *D) {
     // Definition of an enum with an underlying type references declaration for
     // type-checking purposes.
     if (D->isThisDeclarationADefinition() && D->getIntegerTypeSourceInfo())
       report(D->getLocation(), D);
     return true;
   }
 
+  bool VisitConceptDecl(ConceptDecl *CD) {
+    report(CD->getLocation(), CD);
+    return true;
+  }
+
+  bool VisitConceptReference(const ConceptReference *CR) {
+    report(CR->getConceptNameLoc(), CR->getFoundDecl());
+    return true;
+  }
+
   // Report a reference from explicit specializations to the specialized
   // template. Implicit ones are filtered out by RAV and explicit instantiations
   // are already traversed through typelocs.
   bool
   VisitClassTemplateSpecializationDecl(ClassTemplateSpecializationDecl *CTSD) {
     if (CTSD->isExplicitSpecialization())
       report(CTSD->getLocation(),
              CTSD->getSpecializedTemplate()->getTemplatedDecl());

clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp

EXPECT_THAT(
                RefType::Explicit}}),
       UnorderedElementsAre(
           Pair(Code.point("1"), UnorderedElementsAre(HdrFile)),
           Pair(Code.point("2"), UnorderedElementsAre(HdrFile)),
           Pair(Code.point("3"), UnorderedElementsAre(MainFile)),
           Pair(Code.point("4"), UnorderedElementsAre(MainFile))));
 }
 
+TEST_F(WalkUsedTest, Concepts) {
+  llvm::Annotations ConceptHdr(guard(R"cpp(
+    template<typename T>
+    concept Foo = true;
+  )cpp"));
+  llvm::Annotations Code(R"cpp(
+    #include "concept.h"
+
+    template<typename T>
+    concept $Bar1^Bar = $Foo1^Foo<T> && true;
+
+    template<$Bar2^Bar T> requires $Bar3^Bar<T> && $Foo2^Foo<T>
+    void $1^func1() {}
+
+    template<$Foo3^Foo T>
+    void $2^func2() requires $Bar4^Bar<T> {}
+
+    void $3^func3($Bar5^Bar auto x) {
+      $Foo4^Foo auto $y^y = 1;
+    }
+  )cpp");
+  Inputs.Code = Code.code();
+  Inputs.ExtraFiles["concept.h"] = ConceptHdr.code();
+  Inputs.ExtraArgs.push_back("--std=c++20");
+  TestAST AST(Inputs);
+  auto &SM = AST.sourceManager();
+  const auto *ConceptHdrFile = SM.getFileManager().getFile("concept.h").get();
+  auto MainFile = Header(SM.getFileEntryForID(SM.getMainFileID()));
+
+  EXPECT_THAT(
+      offsetToProviders(AST),
+      UnorderedElementsAre(
+          Pair(Code.point("Foo1"), UnorderedElementsAre(ConceptHdrFile)),
+          Pair(Code.point("Foo2"), UnorderedElementsAre(ConceptHdrFile)),
+          Pair(Code.point("Foo3"), UnorderedElementsAre(ConceptHdrFile)),
+          Pair(Code.point("Bar1"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("Bar2"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("Bar3"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("Bar4"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("Bar5"), UnorderedElementsAre(MainFile)),
+          // FIXME: Foo4 should be reported.
+          // Pair(Code.point("Foo4"), UnorderedElementsAre(ConceptHdrFile)),
+          Pair(Code.point("1"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("2"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("3"), UnorderedElementsAre(MainFile)),
+          Pair(Code.point("y"), UnorderedElementsAre(MainFile))))
+      << Code.code();
+}
+
 class AnalyzeTest : public testing::Test {
 protected:
   TestInputs Inputs;
   PragmaIncludes PI;
   RecordedPP PP;
   AnalyzeTest() {
     Inputs.MakeAction = [this] {
       struct Hook : public SyntaxOnlyAction {
)cpp";
   AnalysisResults Results;
   Results.Missing.push_back("\"aa.h\"");
   Results.Missing.push_back("\"ab.h\"");
   Results.Missing.push_back("<e.h>");
   Results.Unused.push_back(Inc.atLine(3));
   Results.Unused.push_back(Inc.atLine(4));
 
   EXPECT_EQ(fixIncludes(Results, "d.cc", Code, format::getLLVMStyle()),
             R"cpp(#include "d.h"
 #include "a.h"
 #include "aa.h"
 #include "ab.h"
 #include <e.h>
 )cpp");
 
   Results = {};
   Results.Missing.push_back("\"d.h\"");
   Code = R"cpp(#include "a.h")cpp";
   EXPECT_EQ(fixIncludes(Results, "d.cc", Code, format::getLLVMStyle()),
             R"cpp(#include "d.h"
 #include "a.h")cpp");
 }
 
 MATCHER_P3(expandedAt, FileID, Offset, SM, "") {
   auto [ExpanedFileID, ExpandedOffset] = SM->getDecomposedExpansionLoc(arg);
   return ExpanedFileID == FileID && ExpandedOffset == Offset;
 }
 MATCHER_P3(spelledAt, FileID, Offset, SM, "") {