[libclang] add supporting for indexing/visiting C++ concepts

[arphaman]

Summary

This patch builds upon recently added indexing support for C++ concepts from https://reviews.llvm.org/D124441 by extending libclang to support indexing and visiting concepts, constraints and requires expressions as well.

[egorzhdan]

Looks like index-concepts.cpp is failing on Windows, @arphaman could you please take a look?

[arphaman]

Yes, I'm going to check what's wrong with it.

[arphaman]

Fix the windows test failure (add -fno-delayed-template-parsing)

[egorzhdan]

I'm not super familiar with concepts but this LGTM, thanks!

[Jake-Egan]

Hi, these tests fail on AIX, could you take a look please?

https://lab.llvm.org/buildbot/#/builders/214/builds/1489

[arphaman]

Sure, investigating.

[arphaman]

@Jake-Egan
Do you happen to have suggestions for how to try to reproduce this? Looking at the failure it looks like this CI job somehow was unable to be affected by this change, for instance the CI output of index-concept-kind.cpp does not have any concepts output:

+ : 'RUN: at line 1'
+ /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/build/bin/c-index-test -index-file /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/llvm-project/clang/test/Index/index-concept-kind.cpp -std=gnu++20
+ /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/build/bin/FileCheck /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/llvm-project/clang/test/Index/index-concept-kind.cpp
/scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/llvm-project/clang/test/Index/index-concept-kind.cpp:5:11: error: CHECK: expected string not found in input
// CHECK: [indexDeclaration]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: ConceptDecl=LargeType:[[@LINE-1]]:9 (Definition) | loc: [[@LINE-1]]:9 | semantic-container: [TU] | lexical-container: [TU] | isRedecl: 0 | isDef: 1 | isContainer: 0 | isImplicit: 0
          ^
<stdin>:1:1: note: scanning from here
[startedTranslationUnit]
^
<stdin>:1:1: note: with "@LINE-1" equal to "4"
[startedTranslationUnit]
^
<stdin>:1:1: note: with "@LINE-1" equal to "4"
[startedTranslationUnit]
^
Input file: <stdin>
Check file: /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/llvm-project/clang/test/Index/index-concept-kind.cpp
-dump-input=help explains the following input dump.
Input was:
<<<<<<
           1: [startedTranslationUnit] 
check:5'0     X~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
check:5'1                               with "@LINE-1" equal to "4"
check:5'2                               with "@LINE-1" equal to "4"
           2: [enteredMainFile]: /scratch/powerllvm/powerllvm_env/aix-ppc64/clang-ppc64-aix/llvm-project/clang/test/Index/index-concept-kind.cpp 
check:5'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           3: [indexDeclaration]: kind: function-template | name: f | USR: c:@FT@>1#Tf#v# | lang: C++ | cursor: FunctionDecl=f:9:6 | loc: 9:6 | semantic-container: [TU] | lexical-container: [TU] | isRedecl: 0 | isDef: 0 | isContainer: 0 | isImplicit: 0 
check:5'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>>

So far I was unable to reproduce this locally, and all the other CI jobs seem to pass.

[arphaman]

@Jake-Egan
I'm going to disable these tests for aix for now to unblock the bot as they're still failing.

[arphaman]

Marked them as unsupported on AIX in 1b34f1e996565bc5e4f2be14b89f881f8fe0f3b9.

[Jake-Egan]

@arphaman Thanks for the quick action. The tests pass on a clean build https://lab.llvm.org/buildbot/#/builders/214/builds/1493, so that's probably why there was trouble reproducing. I think we could revert 1b34f1e996565bc5e4f2be14b89f881f8fe0f3b9.

Reverted: https://reviews.llvm.org/rGbe3fc66f83b0

clang/include/clang-c/Index.h

enum CXCursorKind {
    * OpenMP 5.0 [2.1.6 Iterators]
    */
   CXCursor_OMPIteratorExpr = 151,
 
   /** OpenCL's addrspace_cast<> expression.
    */
   CXCursor_CXXAddrspaceCastExpr = 152,
 
-  CXCursor_LastExpr = CXCursor_CXXAddrspaceCastExpr,
+  /**
+   * Expression that references a C++20 concept.
+   */
+  CXCursor_ConceptSpecializationExpr = 153,
+
+  /**
+   * Expression that references a C++20 concept.
+   */
+  CXCursor_RequiresExpr = 154,
+
+  CXCursor_LastExpr = CXCursor_RequiresExpr,
 
   /* Statements */
   CXCursor_FirstStmt = 200,
   /**
    * A statement whose specific kind is not exposed via this
    * interface.
    *
    * Unexposed statements have the same operations as any other kind of
enum CXCursorKind {
   /**
    * A static_assert or _Static_assert node
    */
   CXCursor_StaticAssert = 602,
   /**
    * a friend declaration.
    */
   CXCursor_FriendDecl = 603,
+  /**
+   * a concept declaration.
+   */
+  CXCursor_ConceptDecl = 604,
+
   CXCursor_FirstExtraDecl = CXCursor_ModuleImportDecl,
-  CXCursor_LastExtraDecl = CXCursor_FriendDecl,
+  CXCursor_LastExtraDecl = CXCursor_ConceptDecl,
 
   /**
    * A code completion overload candidate.
    */
   CXCursor_OverloadCandidate = 700
 };
 
 /**
typedef enum {
   CXIdxEntity_CXXNamespaceAlias = 18,
   CXIdxEntity_CXXStaticVariable = 19,
   CXIdxEntity_CXXStaticMethod = 20,
   CXIdxEntity_CXXInstanceMethod = 21,
   CXIdxEntity_CXXConstructor = 22,
   CXIdxEntity_CXXDestructor = 23,
   CXIdxEntity_CXXConversionFunction = 24,
   CXIdxEntity_CXXTypeAlias = 25,
-  CXIdxEntity_CXXInterface = 26
+  CXIdxEntity_CXXInterface = 26,
+  CXIdxEntity_CXXConcept = 27
 
 } CXIdxEntityKind;
 
 typedef enum {
   CXIdxEntityLang_None = 0,
   CXIdxEntityLang_C = 1,
   CXIdxEntityLang_ObjC = 2,
   CXIdxEntityLang_CXX = 3,

clang/lib/Sema/SemaCodeComplete.cpp

case Decl::ObjCPropertyImpl:
     llvm_unreachable("Unexpected Kind!");
 
   case Decl::Import:
     return CXCursor_ModuleImportDecl;
 
   case Decl::ObjCTypeParam:
     return CXCursor_TemplateTypeParameter;
 
+  case Decl::Concept:
+    return CXCursor_ConceptDecl;
+
   default:
     if (const auto *TD = dyn_cast<TagDecl>(D)) {
       switch (TD->getTagKind()) {
       case TTK_Interface: // fall through
       case TTK_Struct:
         return CXCursor_StructDecl;
       case TTK_Class:
         return CXCursor_ClassDecl;

clang/test/Index/index-concept-kind.cpp

+// RUN: c-index-test -index-file %s -std=gnu++20 | FileCheck %s
+
+template <typename T>
+concept LargeType = sizeof(T) > 8;
+// CHECK: [indexDeclaration]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: ConceptDecl=LargeType:[[@LINE-1]]:9 (Definition) | loc: [[@LINE-1]]:9 | semantic-container: [TU] | lexical-container: [TU] | isRedecl: 0 | isDef: 1 | isContainer: 0 | isImplicit: 0
+
+template <LargeType T>
+// CHECK: [indexEntityReference]: kind: concept | name: LargeType | USR: c:@CT@LargeType | lang: C | cursor: TemplateRef=LargeType:4:9 | loc: [[@LINE-1]]:11 | <parent>:: kind: function-template | name: f | USR: c:@FT@>1#Tf#v# | lang: C++ | container: [<<NULL>>] | refkind: direct | role: ref
+void f();

clang/test/Index/index-concepts.cpp

+// RUN: c-index-test -test-load-source all %s -std=gnu++20 -fno-delayed-template-parsing | FileCheck %s
+
+template<class T>
+struct type_trait {
+    const static bool value = false;
+};
+
+template<>
+struct type_trait<int> {
+    const static bool value = true;
+};
+
+template <class T>
+requires (type_trait<T>::value)
+// CHECK: index-concepts.cpp:[[@LINE-1]]:10: ParenExpr= Extent=[[[@LINE-1]]:10 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-2]]:11: DeclRefExpr= Extent=[[[@LINE-2]]:11 - [[@LINE-2]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:11: TemplateRef=type_trait:4:8 Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:22: TypeRef=T:13:17 Extent=[[[@LINE-4]]:22 - [[@LINE-4]]:23]
+void indexRequiresClause() {
+}
+
+template<class T>
+requires (type_trait<T>::value)
+// CHECK: index-concepts.cpp:[[@LINE-1]]:10: ParenExpr= Extent=[[[@LINE-1]]:10 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-2]]:11: DeclRefExpr= Extent=[[[@LINE-2]]:11 - [[@LINE-2]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:11: TemplateRef=type_trait:4:8 Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:22: TypeRef=T:22:16 Extent=[[[@LINE-4]]:22 - [[@LINE-4]]:23]
+class IndexRequiresClauseInClass {};
+
+template <class T>
+concept Con1 = type_trait<T>::value;
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=Con1:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:18] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:16: DeclRefExpr= Extent=[[[@LINE-3]]:16 - [[@LINE-3]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateRef=type_trait:4:8 Extent=[[[@LINE-4]]:16 - [[@LINE-4]]:26]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:27: TypeRef=T:30:17 Extent=[[[@LINE-5]]:27 - [[@LINE-5]]:28]
+
+constexpr int sizeFunc() { return 4; }
+
+template <class T>
+concept ConWithLogicalAnd = Con1<T> && sizeof(T) > sizeFunc();
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=ConWithLogicalAnd:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:18] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:29: BinaryOperator= Extent=[[[@LINE-3]]:29 - [[@LINE-3]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:29: ConceptSpecializationExpr= Extent=[[[@LINE-4]]:29 - [[@LINE-4]]:36]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:29: TemplateRef=Con1:31:9 Extent=[[[@LINE-5]]:29 - [[@LINE-5]]:33]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:40: BinaryOperator= Extent=[[[@LINE-6]]:40 - [[@LINE-6]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:40: UnaryExpr= Extent=[[[@LINE-7]]:40 - [[@LINE-7]]:49]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:47: TypeRef=T:40:17 Extent=[[[@LINE-8]]:47 - [[@LINE-8]]:48]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:52: UnexposedExpr=sizeFunc:38:15 Extent=[[[@LINE-9]]:52 - [[@LINE-9]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:52: CallExpr=sizeFunc:38:15 Extent=[[[@LINE-10]]:52 - [[@LINE-10]]:62]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:52: UnexposedExpr=sizeFunc:38:15 Extent=[[[@LINE-11]]:52 - [[@LINE-11]]:60]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:52: DeclRefExpr=sizeFunc:38:15 Extent=[[[@LINE-12]]:52 - [[@LINE-12]]:60]
+
+namespace ns {
+
+template <class T>
+concept ConInNamespace = sizeof(T) > 4;
+
+}
+
+template <class T1, class T2>
+concept ConTwoTemplateParams = ns::ConInNamespace<T1> && ConWithLogicalAnd<T2>;
+// CHECK: index-concepts.cpp:[[@LINE-1]]:9: ConceptDecl=ConTwoTemplateParams:[[@LINE-1]]:9 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:17: TemplateTypeParameter=T1:[[@LINE-3]]:17 (Definition) Extent=[[[@LINE-3]]:11 - [[@LINE-3]]:19] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:27: TemplateTypeParameter=T2:[[@LINE-4]]:27 (Definition) Extent=[[[@LINE-4]]:21 - [[@LINE-4]]:29] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:36: BinaryOperator= Extent=[[[@LINE-4]]:36 - [[@LINE-4]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:36: ConceptSpecializationExpr= Extent=[[[@LINE-5]]:36 - [[@LINE-5]]:54]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:32: NamespaceRef=ns:55:11 Extent=[[[@LINE-6]]:32 - [[@LINE-6]]:34]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:36: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-7]]:36 - [[@LINE-7]]:50]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:58: ConceptSpecializationExpr= Extent=[[[@LINE-8]]:58 - [[@LINE-8]]:79]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:58: TemplateRef=ConWithLogicalAnd:41:9 Extent=[[[@LINE-9]]:58 - [[@LINE-9]]:75]
+
+
+struct ConcreteType {};
+
+template<class T>
+requires ConTwoTemplateParams<T, ConcreteType>
+struct UsesConceptInRequires {};
+// CHECK: index-concepts.cpp:[[@LINE-1]]:8: ClassTemplate=UsesConceptInRequires:[[@LINE-1]]:8 (Definition) Extent=[[[@LINE-3]]:1 - [[@LINE-1]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateTypeParameter=T:[[@LINE-4]]:16 (Definition) Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:10: ConceptSpecializationExpr= Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:10: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:31: TypeRef=T:[[@LINE-7]]:16 Extent=[[[@LINE-6]]:31 - [[@LINE-6]]:32]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:34: TypeRef=struct ConcreteType:[[@LINE-10]]:8 Extent=[[[@LINE-7]]:34 - [[@LINE-7]]:46]
+
+
+template<ConWithLogicalAnd T>
+struct UsesConceptInTemplateArg {};
+// CHECK: index-concepts.cpp:[[@LINE-1]]:8: ClassTemplate=UsesConceptInTemplateArg:[[@LINE-1]]:8 (Definition) Extent=[[[@LINE-2]]:1 - [[@LINE-1]]:35]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:28: TemplateTypeParameter=T:[[@LINE-3]]:28 (Definition) Extent=[[[@LINE-3]]:10 - [[@LINE-3]]:29] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:10: TemplateRef=ConWithLogicalAnd:41:9 Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:27]
+
+void usesConceptInAutoParam(ns::ConInNamespace auto x) {}
+// CHECK: index-concepts.cpp:[[@LINE-1]]:6: FunctionTemplate=usesConceptInAutoParam:[[@LINE-1]]:6 (Definition)
+// CHECK: index-concepts.cpp:[[@LINE-2]]:53: ParmDecl=x:[[@LINE-2]]:53 (Definition) Extent=[[[@LINE-2]]:29 - [[@LINE-2]]:54]
+// CHECK: index-concepts.cpp:[[@LINE-3]]:29: NamespaceRef=ns:55:11 Extent=[[[@LINE-3]]:29 - [[@LINE-3]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:33: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-4]]:33 - [[@LINE-4]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:48: TypeRef=ns::ConInNamespace auto:[[@LINE-5]]:53 Extent=[[[@LINE-5]]:48 - [[@LINE-5]]:52]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:56: CompoundStmt= Extent=[[[@LINE-6]]:56 - [[@LINE-6]]:58]
+
+
+template<class T>
+void testTrailingRequires(const T &x)
+requires ns::ConInNamespace<T> && ConTwoTemplateParams<T, ConcreteType> {}
+// CHECK: index-concepts.cpp:[[@LINE-2]]:6: FunctionTemplate=testTrailingRequires:[[@LINE-2]]:6 (Definition) Extent=[[[@LINE-3]]:1 - [[@LINE-1]]:75]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:16: TemplateTypeParameter=T:[[@LINE-4]]:16 (Definition) Extent=[[[@LINE-4]]:10 - [[@LINE-4]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-4]]:36: ParmDecl=x:[[@LINE-4]]:36 (Definition) Extent=[[[@LINE-4]]:27 - [[@LINE-4]]:37]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:33: TypeRef=T:[[@LINE-6]]:16 Extent=[[[@LINE-5]]:33 - [[@LINE-5]]:34]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:14: ConceptSpecializationExpr= Extent=[[[@LINE-5]]:14 - [[@LINE-5]]:31]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:10: NamespaceRef=ns:55:11 Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:12]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:14: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-7]]:14 - [[@LINE-7]]:28]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:29: TypeRef=T:[[@LINE-10]]:16 Extent=[[[@LINE-8]]:29 - [[@LINE-8]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:35: ConceptSpecializationExpr= Extent=[[[@LINE-9]]:35 - [[@LINE-9]]:72]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:35: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-10]]:35 - [[@LINE-10]]:55]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:56: TypeRef=T:[[@LINE-13]]:16 Extent=[[[@LINE-11]]:56 - [[@LINE-11]]:57]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:59: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-12]]:59 - [[@LINE-12]]:71]
+
+
+void concreteFunc(ConcreteType);
+
+template<class T>
+void genericFunc(const T&x);
+
+template<class T>
+concept ConWithRequires = requires(const T& x, ConcreteType value) {
+  concreteFunc(value);
+  genericFunc(x);
+};
+// CHECK: index-concepts.cpp:[[@LINE-4]]:9: ConceptDecl=ConWithRequires:[[@LINE-4]]:9 (Definition) Extent=[[[@LINE-5]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateTypeParameter=T:[[@LINE-6]]:16 (Definition) Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:27: RequiresExpr= Extent=[[[@LINE-6]]:27 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:61: ParmDecl=value:[[@LINE-7]]:61 (Definition) Extent=[[[@LINE-7]]:48 - [[@LINE-7]]:66]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:48: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-8]]:48 - [[@LINE-8]]:60]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:45: ParmDecl=x:[[@LINE-9]]:45 (Definition) Extent=[[[@LINE-9]]:36 - [[@LINE-9]]:46]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:42: TypeRef=T:[[@LINE-11]]:16 Extent=[[[@LINE-10]]:42 - [[@LINE-10]]:43]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:3: UnexposedExpr=concreteFunc:[[@LINE-17]]:6 Extent=[[[@LINE-10]]:3 - [[@LINE-10]]:15]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:3: DeclRefExpr=concreteFunc:[[@LINE-18]]:6 Extent=[[[@LINE-11]]:3 - [[@LINE-11]]:15]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:16: CallExpr=ConcreteType:75:8 Extent=[[[@LINE-12]]:16 - [[@LINE-12]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-13]]:16: UnexposedExpr=value:[[@LINE-14]]:61 Extent=[[[@LINE-13]]:16 - [[@LINE-13]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:16: DeclRefExpr=value:[[@LINE-15]]:61 Extent=[[[@LINE-14]]:16 - [[@LINE-14]]:21]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:3: DeclRefExpr=[[[@LINE-19]]:6] Extent=[[[@LINE-14]]:3 - [[@LINE-14]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-15]]:3: OverloadedDeclRef=genericFunc[[[@LINE-20]]:6] Extent=[[[@LINE-15]]:3 - [[@LINE-15]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-16]]:15: DeclRefExpr=x:[[@LINE-18]]:45 Extent=[[[@LINE-16]]:15 - [[@LINE-16]]:16]
+
+template<class T>
+concept ConWithCompRequires = requires {
+  { genericFunc(T()) } -> ns::ConInNamespace;
+  { genericFunc(T()) } -> ConTwoTemplateParams<ConcreteType>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-4]]:9: ConceptDecl=ConWithCompRequires:[[@LINE-4]]:9 (Definition) Extent=[[[@LINE-5]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateTypeParameter=T:[[@LINE-6]]:16 (Definition) Extent=[[[@LINE-6]]:10 - [[@LINE-6]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:31: RequiresExpr= Extent=[[[@LINE-6]]:31 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:5: DeclRefExpr=[123:6] Extent=[[[@LINE-6]]:5 - [[@LINE-6]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:5: OverloadedDeclRef=genericFunc[123:6] Extent=[[[@LINE-7]]:5 - [[@LINE-7]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-8]]:17: CallExpr= Extent=[[[@LINE-8]]:17 - [[@LINE-8]]:20]
+// CHECK: index-concepts.cpp:[[@LINE-9]]:17: TypeRef=T:[[@LINE-11]]:16 Extent=[[[@LINE-9]]:17 - [[@LINE-9]]:18]
+// CHECK: index-concepts.cpp:[[@LINE-10]]:27: NamespaceRef=ns:55:11 Extent=[[[@LINE-10]]:27 - [[@LINE-10]]:29]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:31: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-11]]:31 - [[@LINE-11]]:45]
+// CHECK: index-concepts.cpp:[[@LINE-11]]:5: DeclRefExpr=[123:6] Extent=[[[@LINE-11]]:5 - [[@LINE-11]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-12]]:5: OverloadedDeclRef=genericFunc[123:6] Extent=[[[@LINE-12]]:5 - [[@LINE-12]]:16]
+// CHECK: index-concepts.cpp:[[@LINE-13]]:17: CallExpr= Extent=[[[@LINE-13]]:17 - [[@LINE-13]]:20]
+// CHECK: index-concepts.cpp:[[@LINE-14]]:17: TypeRef=T:[[@LINE-17]]:16 Extent=[[[@LINE-14]]:17 - [[@LINE-14]]:18]
+// CHECK: index-concepts.cpp:[[@LINE-15]]:27: TemplateRef=ConTwoTemplateParams:63:9 Extent=[[[@LINE-15]]:27 - [[@LINE-15]]:47]
+// CHECK: index-concepts.cpp:[[@LINE-16]]:48: TypeRef=struct ConcreteType:75:8 Extent=[[[@LINE-16]]:48 - [[@LINE-16]]:60]
+
+template<class T>
+concept ConWithTypeReq = requires {
+  typename type_trait<T>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-3]]:9: ConceptDecl=ConWithTypeReq:[[@LINE-3]]:9 (Definition) Extent=[[[@LINE-4]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:16: TemplateTypeParameter=T:[[@LINE-5]]:16 (Definition) Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:26: RequiresExpr= Extent=[[[@LINE-5]]:26 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:12: TemplateRef=type_trait:4:8 Extent=[[[@LINE-5]]:12 - [[@LINE-5]]:22]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:23: TypeRef=T:[[@LINE-8]]:16 Extent=[[[@LINE-6]]:23 - [[@LINE-6]]:24]
+
+template<class T>
+concept ConWithNestedReq = requires {
+  requires ns::ConInNamespace<T>;
+};
+// CHECK: index-concepts.cpp:[[@LINE-3]]:9: ConceptDecl=ConWithNestedReq:[[@LINE-3]]:9 (Definition) Extent=[[[@LINE-4]]:1 - [[@LINE-1]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:16: TemplateTypeParameter=T:[[@LINE-5]]:16 (Definition) Extent=[[[@LINE-5]]:10 - [[@LINE-5]]:17] [access=public]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:28: RequiresExpr= Extent=[[[@LINE-5]]:28 - [[@LINE-3]]:2]
+// CHECK: index-concepts.cpp:[[@LINE-5]]:12: NamespaceRef=ns:55:11 Extent=[[[@LINE-5]]:12 - [[@LINE-5]]:14]
+// CHECK: index-concepts.cpp:[[@LINE-6]]:16: TemplateRef=ConInNamespace:58:9 Extent=[[[@LINE-6]]:16 - [[@LINE-6]]:30]
+// CHECK: index-concepts.cpp:[[@LINE-7]]:31: TypeRef=T:[[@LINE-9]]:16 Extent=[[[@LINE-7]]:31 - [[@LINE-7]]:32]

clang/tools/c-index-test/c-index-test.c

static const char *getEntityKindString(CXIdxEntityKind kind) {
   case CXIdxEntity_CXXStaticVariable: return "c++-static-var";
   case CXIdxEntity_CXXStaticMethod: return "c++-static-method";
   case CXIdxEntity_CXXInstanceMethod: return "c++-instance-method";
   case CXIdxEntity_CXXConstructor: return "constructor";
   case CXIdxEntity_CXXDestructor: return "destructor";
   case CXIdxEntity_CXXConversionFunction: return "conversion-func";
   case CXIdxEntity_CXXTypeAlias: return "type-alias";
   case CXIdxEntity_CXXInterface: return "c++-__interface";
+  case CXIdxEntity_CXXConcept:
+    return "concept";
   }
   assert(0 && "Garbage entity kind");
   return 0;
 }
 
 static const char *getEntityTemplateKindString(CXIdxEntityCXXTemplateKind kind) {
   switch (kind) {
   case CXIdxEntity_NonTemplate: return "";

clang/tools/libclang/CIndex.cpp

bool CursorVisitor::VisitClassTemplatePartialSpecializationDecl(
   for (unsigned I = 0, N = Info->NumTemplateArgs; I != N; ++I)
     if (VisitTemplateArgumentLoc(TemplateArgs[I]))
       return true;
 
   return VisitCXXRecordDecl(D);
 }
 
 bool CursorVisitor::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
-  if (const auto *TC = D->getTypeConstraint())
-    if (Visit(MakeCXCursor(TC->getImmediatelyDeclaredConstraint(), StmtParent,
-                           TU, RegionOfInterest)))
+  if (const auto *TC = D->getTypeConstraint()) {
+    if (VisitTypeConstraint(*TC))
       return true;
+  }
 
   // Visit the default argument.
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited())
     if (TypeSourceInfo *DefArg = D->getDefaultArgumentInfo())
       if (Visit(DefArg->getTypeLoc()))
         return true;
 
   return false;
if (TypeSourceInfo *TSInfo = ND->getTypeSourceInfo()) {
 
     // Visit the function's trailing return type.
     if (FTL && HasTrailingRT && Visit(FTL.getReturnLoc()))
       return true;
 
     // FIXME: Attributes?
   }
 
+  if (auto *E = ND->getTrailingRequiresClause()) {
+    if (Visit(E))
+      return true;
+  }
+
   if (ND->doesThisDeclarationHaveABody() && !ND->isLateTemplateParsed()) {
     if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(ND)) {
       // Find the initializers that were written in the source.
       SmallVector<CXXCtorInitializer *, 4> WrittenInits;
       for (auto *I : Constructor->inits()) {
         if (!I->isWritten())
           continue;
 

 bool CursorVisitor::VisitDecompositionDecl(DecompositionDecl *D) {
   for (auto *B : D->bindings()) {
     if (Visit(MakeCXCursor(B, TU, RegionOfInterest)))
       return true;
   }
   return VisitVarDecl(D);
 }
 
+bool CursorVisitor::VisitConceptDecl(ConceptDecl *D) {
+  if (VisitTemplateParameters(D->getTemplateParameters()))
+    return true;
+
+  if (auto *E = D->getConstraintExpr()) {
+    if (Visit(MakeCXCursor(E, D, TU, RegionOfInterest)))
+      return true;
+  }
+  return false;
+}
+
+bool CursorVisitor::VisitTypeConstraint(const TypeConstraint &TC) {
+  if (TC.getNestedNameSpecifierLoc()) {
+    if (VisitNestedNameSpecifierLoc(TC.getNestedNameSpecifierLoc()))
+      return true;
+  }
+  if (TC.getNamedConcept()) {
+    if (Visit(MakeCursorTemplateRef(TC.getNamedConcept(),
+                                    TC.getConceptNameLoc(), TU)))
+      return true;
+  }
+  if (auto Args = TC.getTemplateArgsAsWritten()) {
+    for (const auto &Arg : Args->arguments()) {
+      if (VisitTemplateArgumentLoc(Arg))
+        return true;
+    }
+  }
+  return false;
+}
+
+bool CursorVisitor::VisitConceptRequirement(const concepts::Requirement &R) {
+  using namespace concepts;
+  switch (R.getKind()) {
+  case Requirement::RK_Type: {
+    const TypeRequirement &TR = cast<TypeRequirement>(R);
+    if (!TR.isSubstitutionFailure()) {
+      if (Visit(TR.getType()->getTypeLoc()))
+        return true;
+    }
+    break;
+  }
+  case Requirement::RK_Simple:
+  case Requirement::RK_Compound: {
+    const ExprRequirement &ER = cast<ExprRequirement>(R);
+    if (!ER.isExprSubstitutionFailure()) {
+      if (Visit(ER.getExpr()))
+        return true;
+    }
+    if (ER.getKind() == Requirement::RK_Compound) {
+      const auto &RTR = ER.getReturnTypeRequirement();
+      if (RTR.isTypeConstraint()) {
+        if (const auto *Cons = RTR.getTypeConstraint())
+          VisitTypeConstraint(*Cons);
+      }
+    }
+    break;
+  }
+  case Requirement::RK_Nested: {
+    const NestedRequirement &NR = cast<NestedRequirement>(R);
+    if (!NR.isSubstitutionFailure()) {
+      if (Visit(NR.getConstraintExpr()))
+        return true;
+    }
+    break;
+  }
+  }
+  return false;
+}
+
 bool CursorVisitor::VisitDeclarationNameInfo(DeclarationNameInfo Name) {
   switch (Name.getName().getNameKind()) {
   case clang::DeclarationName::Identifier:
   case clang::DeclarationName::CXXLiteralOperatorName:
   case clang::DeclarationName::CXXDeductionGuideName:
   case clang::DeclarationName::CXXOperatorName:
   case clang::DeclarationName::CXXUsingDirective:
     return false;
bool CursorVisitor::VisitTemplateParameters(
 
   for (TemplateParameterList::const_iterator P = Params->begin(),
                                              PEnd = Params->end();
        P != PEnd; ++P) {
     if (Visit(MakeCXCursor(*P, TU, RegionOfInterest)))
       return true;
   }
 
+  if (const auto *E = Params->getRequiresClause()) {
+    if (Visit(MakeCXCursor(Params->getRequiresClause(), nullptr, TU,
+                           RegionOfInterest)))
+      return true;
+  }
+
   return false;
 }
 
 bool CursorVisitor::VisitTemplateName(TemplateName Name, SourceLocation Loc) {
   switch (Name.getKind()) {
   case TemplateName::Template:
   case TemplateName::UsingTemplate:
   case TemplateName::QualifiedTemplate: // FIXME: Visit nested-name-specifier.

 bool CursorVisitor::VisitTagTypeLoc(TagTypeLoc TL) {
   if (TL.isDefinition())
     return Visit(MakeCXCursor(TL.getDecl(), TU, RegionOfInterest));
 
   return Visit(MakeCursorTypeRef(TL.getDecl(), TL.getNameLoc(), TU));
 }
 
 bool CursorVisitor::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
+  if (const auto *TC = TL.getDecl()->getTypeConstraint()) {
+    if (VisitTypeConstraint(*TC))
+      return true;
+  }
+
   return Visit(MakeCursorTypeRef(TL.getDecl(), TL.getNameLoc(), TU));
 }
 
 bool CursorVisitor::VisitObjCInterfaceTypeLoc(ObjCInterfaceTypeLoc TL) {
   return Visit(MakeCursorObjCClassRef(TL.getIFaceDecl(), TL.getNameLoc(), TU));
 }
 
 bool CursorVisitor::VisitObjCTypeParamTypeLoc(ObjCTypeParamTypeLoc TL) {
#define DEF_JOB(NAME, DATA, KIND)                                              \
   };
 
 DEF_JOB(StmtVisit, Stmt, StmtVisitKind)
 DEF_JOB(MemberExprParts, MemberExpr, MemberExprPartsKind)
 DEF_JOB(DeclRefExprParts, DeclRefExpr, DeclRefExprPartsKind)
 DEF_JOB(OverloadExprParts, OverloadExpr, OverloadExprPartsKind)
 DEF_JOB(SizeOfPackExprParts, SizeOfPackExpr, SizeOfPackExprPartsKind)
 DEF_JOB(LambdaExprParts, LambdaExpr, LambdaExprPartsKind)
+DEF_JOB(ConceptSpecializationExprVisit, ConceptSpecializationExpr,
+        ConceptSpecializationExprVisitKind)
+DEF_JOB(RequiresExprVisit, RequiresExpr, RequiresExprVisitKind)
 DEF_JOB(PostChildrenVisit, void, PostChildrenVisitKind)
 #undef DEF_JOB
 
 class ExplicitTemplateArgsVisit : public VisitorJob {
 public:
   ExplicitTemplateArgsVisit(const TemplateArgumentLoc *Begin,
                             const TemplateArgumentLoc *End, CXCursor parent)
       : VisitorJob(parent, VisitorJob::ExplicitTemplateArgsVisitKind, Begin,
public:
   void VisitArrayTypeTraitExpr(const ArrayTypeTraitExpr *E);
   void VisitExpressionTraitExpr(const ExpressionTraitExpr *E);
   void VisitUnresolvedMemberExpr(const UnresolvedMemberExpr *U);
   void VisitVAArgExpr(const VAArgExpr *E);
   void VisitSizeOfPackExpr(const SizeOfPackExpr *E);
   void VisitPseudoObjectExpr(const PseudoObjectExpr *E);
   void VisitOpaqueValueExpr(const OpaqueValueExpr *E);
   void VisitLambdaExpr(const LambdaExpr *E);
+  void VisitConceptSpecializationExpr(const ConceptSpecializationExpr *E);
+  void VisitRequiresExpr(const RequiresExpr *E);
   void VisitOMPExecutableDirective(const OMPExecutableDirective *D);
   void VisitOMPLoopBasedDirective(const OMPLoopBasedDirective *D);
   void VisitOMPLoopDirective(const OMPLoopDirective *D);
   void VisitOMPParallelDirective(const OMPParallelDirective *D);
   void VisitOMPSimdDirective(const OMPSimdDirective *D);
   void
   VisitOMPLoopTransformationDirective(const OMPLoopTransformationDirective *D);
   void VisitOMPTileDirective(const OMPTileDirective *D);
void EnqueueVisitor::VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
   // visit that.  This is useful for (e.g.) pseudo-object expressions.
   if (Expr *SourceExpr = E->getSourceExpr())
     return Visit(SourceExpr);
 }
 void EnqueueVisitor::VisitLambdaExpr(const LambdaExpr *E) {
   AddStmt(E->getBody());
   WL.push_back(LambdaExprParts(E, Parent));
 }
+void EnqueueVisitor::VisitConceptSpecializationExpr(
+    const ConceptSpecializationExpr *E) {
+  WL.push_back(ConceptSpecializationExprVisit(E, Parent));
+}
+void EnqueueVisitor::VisitRequiresExpr(const RequiresExpr *E) {
+  WL.push_back(RequiresExprVisit(E, Parent));
+  for (ParmVarDecl *VD : E->getLocalParameters())
+    AddDecl(VD);
+}
 void EnqueueVisitor::VisitPseudoObjectExpr(const PseudoObjectExpr *E) {
   // Treat the expression like its syntactic form.
   Visit(E->getSyntacticForm());
 }
 
 void EnqueueVisitor::VisitOMPExecutableDirective(
     const OMPExecutableDirective *D) {
   EnqueueChildren(D);
case VisitorJob::LambdaExprPartsKind: {
           // Visit result type.
           if (Visit(Proto.getReturnLoc()))
             return true;
         }
       }
       break;
     }
 
+    case VisitorJob::ConceptSpecializationExprVisitKind: {
+      const ConceptSpecializationExpr *E =
+          cast<ConceptSpecializationExprVisit>(&LI)->get();
+      if (NestedNameSpecifierLoc QualifierLoc =
+              E->getNestedNameSpecifierLoc()) {
+        if (VisitNestedNameSpecifierLoc(QualifierLoc))
+          return true;
+      }
+
+      if (E->getNamedConcept() &&
+          Visit(MakeCursorTemplateRef(E->getNamedConcept(),
+                                      E->getConceptNameLoc(), TU)))
+        return true;
+
+      if (auto Args = E->getTemplateArgsAsWritten()) {
+        for (const auto &Arg : Args->arguments()) {
+          if (VisitTemplateArgumentLoc(Arg))
+            return true;
+        }
+      }
+      break;
+    }
+
+    case VisitorJob::RequiresExprVisitKind: {
+      const RequiresExpr *E = cast<RequiresExprVisit>(&LI)->get();
+      for (const concepts::Requirement *R : E->getRequirements())
+        VisitConceptRequirement(*R);
+      break;
+    }
+
     case VisitorJob::PostChildrenVisitKind:
       if (PostChildrenVisitor(Parent, ClientData))
         return true;
       break;
     }
   }
   return false;
 }
CXString clang_getCursorKindSpelling(enum CXCursorKind Kind) {
   case CXCursor_MemberRefExpr:
     return cxstring::createRef("MemberRefExpr");
   case CXCursor_CallExpr:
     return cxstring::createRef("CallExpr");
   case CXCursor_ObjCMessageExpr:
     return cxstring::createRef("ObjCMessageExpr");
   case CXCursor_BuiltinBitCastExpr:
     return cxstring::createRef("BuiltinBitCastExpr");
+  case CXCursor_ConceptSpecializationExpr:
+    return cxstring::createRef("ConceptSpecializationExpr");
+  case CXCursor_RequiresExpr:
+    return cxstring::createRef("RequiresExpr");
   case CXCursor_UnexposedStmt:
     return cxstring::createRef("UnexposedStmt");
   case CXCursor_DeclStmt:
     return cxstring::createRef("DeclStmt");
   case CXCursor_LabelStmt:
     return cxstring::createRef("LabelStmt");
   case CXCursor_CompoundStmt:
     return cxstring::createRef("CompoundStmt");
CXString clang_getCursorKindSpelling(enum CXCursorKind Kind) {
   case CXCursor_ConvergentAttr:
     return cxstring::createRef("attribute(convergent)");
   case CXCursor_WarnUnusedAttr:
     return cxstring::createRef("attribute(warn_unused)");
   case CXCursor_WarnUnusedResultAttr:
     return cxstring::createRef("attribute(warn_unused_result)");
   case CXCursor_AlignedAttr:
     return cxstring::createRef("attribute(aligned)");
+  case CXCursor_ConceptDecl:
+    return cxstring::createRef("ConceptDecl");
   }
 
   llvm_unreachable("Unhandled CXCursorKind");
 }
 
 struct GetCursorData {
   SourceLocation TokenBeginLoc;
   bool PointsAtMacroArgExpansion;

clang/tools/libclang/CXCursor.cpp

case Stmt::CoreturnStmtClass:
     break;
 
   case Stmt::ArrayTypeTraitExprClass:
   case Stmt::AsTypeExprClass:
   case Stmt::AtomicExprClass:
   case Stmt::BinaryConditionalOperatorClass:
   case Stmt::TypeTraitExprClass:
   case Stmt::CoawaitExprClass:
-  case Stmt::ConceptSpecializationExprClass:
-  case Stmt::RequiresExprClass:
   case Stmt::DependentCoawaitExprClass:
   case Stmt::CoyieldExprClass:
   case Stmt::CXXBindTemporaryExprClass:
   case Stmt::CXXDefaultArgExprClass:
   case Stmt::CXXDefaultInitExprClass:
   case Stmt::CXXFoldExprClass:
   case Stmt::CXXRewrittenBinaryOperatorClass:
   case Stmt::CXXStdInitializerListExprClass:
if (RegionOfInterest.isValid() &&
           llvm::find(SelLocs, RegionOfInterest.getBegin());
       if (I != SelLocs.end())
         SelectorIdIndex = I - SelLocs.begin();
     }
     CXCursor C = {K, 0, {Parent, S, TU}};
     return getSelectorIdentifierCursor(SelectorIdIndex, C);
   }
 
+  case Stmt::ConceptSpecializationExprClass:
+    K = CXCursor_ConceptSpecializationExpr;
+    break;
+
+  case Stmt::RequiresExprClass:
+    K = CXCursor_RequiresExpr;
+    break;
+
   case Stmt::MSDependentExistsStmtClass:
     K = CXCursor_UnexposedStmt;
     break;
   case Stmt::OMPCanonicalLoopClass:
     K = CXCursor_OMPCanonicalLoop;
     break;
   case Stmt::OMPMetaDirectiveClass:
     K = CXCursor_OMPMetaDirective;

clang/tools/libclang/CXIndexDataConsumer.h

public:
   bool handleObjCProperty(const ObjCPropertyDecl *D);
 
   bool handleNamespace(const NamespaceDecl *D);
 
   bool handleClassTemplate(const ClassTemplateDecl *D);
   bool handleFunctionTemplate(const FunctionTemplateDecl *D);
   bool handleTypeAliasTemplate(const TypeAliasTemplateDecl *D);
 
+  bool handleConcept(const ConceptDecl *D);
+
   bool handleReference(const NamedDecl *D, SourceLocation Loc, CXCursor Cursor,
                        const NamedDecl *Parent,
                        const DeclContext *DC,
                        const Expr *E = nullptr,
                        CXIdxEntityRefKind Kind = CXIdxEntityRef_Direct,
                        CXSymbolRole Role = CXSymbolRole_None);
 
   bool isNotFromSourceFile(SourceLocation Loc) const;

clang/tools/libclang/CXIndexDataConsumer.cpp

bool VisitTypeAliasTemplateDecl(const TypeAliasTemplateDecl *D) {
     DataConsumer.handleTypeAliasTemplate(D);
     return true;
   }
 
   bool VisitImportDecl(const ImportDecl *D) {
     DataConsumer.importedModule(D);
     return true;
   }
+
+  bool VisitConceptDecl(const ConceptDecl *D) {
+    DataConsumer.handleConcept(D);
+    return true;
+  }
 };
 
 CXSymbolRole getSymbolRole(SymbolRoleSet Role) {
   // CXSymbolRole mirrors low 9 bits of clang::index::SymbolRole.
   return CXSymbolRole(static_cast<uint32_t>(Role) & ((1 << 9) - 1));
 }
 }
 

 }
 
 bool CXIndexDataConsumer::handleTypeAliasTemplate(const TypeAliasTemplateDecl *D) {
   DeclInfo DInfo(/*isRedeclaration=*/!D->isCanonicalDecl(),
                  /*isDefinition=*/true, /*isContainer=*/false);
   return handleDecl(D, D->getLocation(), getCursor(D), DInfo);
 }
 
+bool CXIndexDataConsumer::handleConcept(const ConceptDecl *D) {
+  DeclInfo DInfo(/*isRedeclaration=*/!D->isCanonicalDecl(),
+                 /*isDefinition=*/true, /*isContainer=*/false);
+  return handleDecl(D, D->getLocation(), getCursor(D), DInfo);
+}
+
 bool CXIndexDataConsumer::handleReference(const NamedDecl *D, SourceLocation Loc,
                                       CXCursor Cursor,
                                       const NamedDecl *Parent,
                                       const DeclContext *DC,
                                       const Expr *E,
                                       CXIdxEntityRefKind Kind,
                                       CXSymbolRole Role) {
   if (!CB.indexEntityReference)
static CXIdxEntityKind getEntityKindFromSymbolKind(SymbolKind K, SymbolLanguage Lang) {
   case SymbolKind::Unknown:
   case SymbolKind::Module:
   case SymbolKind::Macro:
   case SymbolKind::ClassProperty:
   case SymbolKind::Using:
   case SymbolKind::TemplateTypeParm:
   case SymbolKind::TemplateTemplateParm:
   case SymbolKind::NonTypeTemplateParm:
-  case SymbolKind::Concept:
     return CXIdxEntity_Unexposed;
 
   case SymbolKind::Enum: return CXIdxEntity_Enum;
   case SymbolKind::Struct: return CXIdxEntity_Struct;
   case SymbolKind::Union: return CXIdxEntity_Union;
   case SymbolKind::TypeAlias:
     if (Lang == SymbolLanguage::CXX)
       return CXIdxEntity_CXXTypeAlias;
static CXIdxEntityKind getEntityKindFromSymbolKind(SymbolKind K, SymbolLanguage Lang) {
   case SymbolKind::InstanceProperty: return CXIdxEntity_ObjCProperty;
   case SymbolKind::StaticProperty: return CXIdxEntity_CXXStaticVariable;
   case SymbolKind::Namespace: return CXIdxEntity_CXXNamespace;
   case SymbolKind::NamespaceAlias: return CXIdxEntity_CXXNamespaceAlias;
   case SymbolKind::Constructor: return CXIdxEntity_CXXConstructor;
   case SymbolKind::Destructor: return CXIdxEntity_CXXDestructor;
   case SymbolKind::ConversionFunction: return CXIdxEntity_CXXConversionFunction;
   case SymbolKind::Parameter: return CXIdxEntity_Variable;
+  case SymbolKind::Concept:
+    return CXIdxEntity_CXXConcept;
   }
   llvm_unreachable("invalid symbol kind");
 }
 
 static CXIdxEntityCXXTemplateKind
 getEntityKindFromSymbolProperties(SymbolPropertySet K) {
   if (K & (SymbolPropertySet)SymbolProperty::TemplatePartialSpecialization)
     return CXIdxEntity_TemplatePartialSpecialization;

clang/tools/libclang/CursorVisitor.h

 #include "Index_Internal.h"
 #include "clang/AST/DeclVisitor.h"
 #include "clang/AST/TypeLocVisitor.h"
 
 namespace clang {
 class PreprocessingRecord;
 class ASTUnit;
 
+namespace concepts {
+class Requirement;
+}
+
 namespace cxcursor {
 
 class VisitorJob {
 public:
   enum Kind {
     DeclVisitKind,
     StmtVisitKind,
     MemberExprPartsKind,
     TypeLocVisitKind,
     OverloadExprPartsKind,
     DeclRefExprPartsKind,
     LabelRefVisitKind,
     ExplicitTemplateArgsVisitKind,
     NestedNameSpecifierLocVisitKind,
     DeclarationNameInfoVisitKind,
     MemberRefVisitKind,
     SizeOfPackExprPartsKind,
     LambdaExprPartsKind,
+    ConceptSpecializationExprVisitKind,
+    RequiresExprVisitKind,
     PostChildrenVisitKind
   };
 
 protected:
   const void *data[3];
   CXCursor parent;
   Kind K;
   VisitorJob(CXCursor C, Kind k, const void *d1, const void *d2 = nullptr,
public:
   bool VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
   bool VisitUsingDirectiveDecl(UsingDirectiveDecl *D);
   bool VisitUsingDecl(UsingDecl *D);
   bool VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
   bool VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
   bool VisitStaticAssertDecl(StaticAssertDecl *D);
   bool VisitFriendDecl(FriendDecl *D);
   bool VisitDecompositionDecl(DecompositionDecl *D);
+  bool VisitConceptDecl(ConceptDecl *D);
+  bool VisitTypeConstraint(const TypeConstraint &TC);
+  bool VisitConceptRequirement(const concepts::Requirement &R);
 
   // Name visitor
   bool VisitDeclarationNameInfo(DeclarationNameInfo Name);
   bool VisitNestedNameSpecifier(NestedNameSpecifier *NNS, SourceRange Range);
   bool VisitNestedNameSpecifierLoc(NestedNameSpecifierLoc NNS);
 
   // Template visitors
   bool VisitTemplateParameters(const TemplateParameterList *Params);