java/dagger/internal/codegen/xprocessing/XElements.java - platform/external/dagger2 - Git at Google

 /*
  * Copyright (C) 2021 The Dagger Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package dagger.internal.codegen.xprocessing;

 import static androidx.room.compiler.processing.XElementKt.isConstructor;
 import static androidx.room.compiler.processing.XElementKt.isField;
 import static androidx.room.compiler.processing.XElementKt.isMethod;
 import static androidx.room.compiler.processing.XElementKt.isMethodParameter;
 import static androidx.room.compiler.processing.XElementKt.isTypeElement;
 import static androidx.room.compiler.processing.XElementKt.isVariableElement;
 import static androidx.room.compiler.processing.compat.XConverters.getProcessingEnv;
 import static androidx.room.compiler.processing.compat.XConverters.toJavac;
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 import static dagger.internal.codegen.extension.DaggerStreams.toImmutableSet;
 import static java.util.stream.Collectors.joining;

 import androidx.room.compiler.processing.XAnnotated;
 import androidx.room.compiler.processing.XAnnotation;
 import androidx.room.compiler.processing.XConstructorElement;
 import androidx.room.compiler.processing.XElement;
 import androidx.room.compiler.processing.XEnumEntry;
 import androidx.room.compiler.processing.XEnumTypeElement;
 import androidx.room.compiler.processing.XExecutableElement;
 import androidx.room.compiler.processing.XExecutableParameterElement;
 import androidx.room.compiler.processing.XFieldElement;
 import androidx.room.compiler.processing.XHasModifiers;
 import androidx.room.compiler.processing.XMemberContainer;
 import androidx.room.compiler.processing.XMethodElement;
 import androidx.room.compiler.processing.XProcessingEnv;
 import androidx.room.compiler.processing.XTypeElement;
 import androidx.room.compiler.processing.XTypeParameterElement;
 import androidx.room.compiler.processing.XVariableElement;
 import com.google.auto.common.MoreElements;
 import com.google.common.collect.ImmutableSet;
 import com.squareup.javapoet.ClassName;
 import java.util.Collection;
 import java.util.Optional;
 import javax.lang.model.element.Element;
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.QualifiedNameable;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
 import javax.lang.model.type.ArrayType;
 import javax.lang.model.type.DeclaredType;
 import javax.lang.model.type.ErrorType;
 import javax.lang.model.type.ExecutableType;
 import javax.lang.model.type.IntersectionType;
 import javax.lang.model.type.NoType;
 import javax.lang.model.type.PrimitiveType;
 import javax.lang.model.type.TypeMirror;
 import javax.lang.model.type.TypeVariable;
 import javax.lang.model.type.WildcardType;
 import javax.lang.model.util.SimpleTypeVisitor8;

 // TODO(bcorso): Consider moving these methods into XProcessing library.
 /** A utility class for {@link XElement} helper methods. */
 public final class XElements {

   // TODO(bcorso): Replace usages with getJvmName() once it exists.
   /** Returns the simple name of the member container. */
   public static String getSimpleName(XMemberContainer memberContainer) {
     return memberContainer.getClassName().simpleName();
   }

   /** Returns the simple name of the element. */
   public static String getSimpleName(XElement element) {
     if (isTypeElement(element)) {
       return asTypeElement(element)
           .getName(); // SUPPRESS_GET_NAME_CHECK: This uses java simple name implementation under
       // the hood.
     } else if (isVariableElement(element)) {
       return asVariable(element).getName(); // SUPPRESS_GET_NAME_CHECK
     } else if (isEnumEntry(element)) {
       return asEnumEntry(element).getName(); // SUPPRESS_GET_NAME_CHECK
     } else if (isMethod(element)) {
       return asMethod(element).getJvmName();
     } else if (isConstructor(element)) {
       return "<init>";
     }
     throw new AssertionError("No simple name for: " + element);
   }

   /**
    * Returns the closest enclosing element that is a {@link XTypeElement} or throws an {@link
    * IllegalStateException} if one doesn't exists.
    */
   public static XTypeElement closestEnclosingTypeElement(XElement element) {
     return optionalClosestEnclosingTypeElement(element)
         .orElseThrow(() -> new IllegalStateException("No enclosing TypeElement for: " + element));
   }

   /**
    * Returns {@code true} if {@code encloser} is equal to or transitively encloses {@code enclosed}.
    */
   public static boolean transitivelyEncloses(XElement encloser, XElement enclosed) {
     XElement current = enclosed;
     while (current != null) {
       if (current.equals(encloser)) {
         return true;
       }
       current = current.getEnclosingElement();
     }
     return false;
   }

   private static Optional<XTypeElement> optionalClosestEnclosingTypeElement(XElement element) {
     if (isTypeElement(element)) {
       return Optional.of(asTypeElement(element));
     } else if (isConstructor(element)) {
       return Optional.of(asConstructor(element).getEnclosingElement());
     } else if (isMethod(element)) {
       return optionalClosestEnclosingTypeElement(asMethod(element).getEnclosingElement());
     } else if (isField(element)) {
       return optionalClosestEnclosingTypeElement(asField(element).getEnclosingElement());
     } else if (isMethodParameter(element)) {
       return optionalClosestEnclosingTypeElement(asMethodParameter(element).getEnclosingElement());
     }
     return Optional.empty();
   }

   public static boolean isAbstract(XElement element) {
     return asHasModifiers(element).isAbstract();
   }

   public static boolean isPublic(XElement element) {
     return asHasModifiers(element).isPublic();
   }

   public static boolean isPrivate(XElement element) {
     return asHasModifiers(element).isPrivate();
   }

   public static boolean isStatic(XElement element) {
     return asHasModifiers(element).isStatic();
   }

   // TODO(bcorso): Ideally we would modify XElement to extend XHasModifiers to prevent possible
   // runtime exceptions if the element does not extend XHasModifiers. However, for Dagger's purpose
   // all usages should be on elements that do extend XHasModifiers, so generalizing this for
   // XProcessing is probably overkill for now.
   private static XHasModifiers asHasModifiers(XElement element) {
     // In javac, Element implements HasModifiers but in XProcessing XElement does not.
     // Currently, the elements that do not extend XHasModifiers are XMemberContainer, XEnumEntry,
     // XVariableElement. Though most instances of XMemberContainer will extend XHasModifiers through
     // XTypeElement instead.
     checkArgument(element instanceof XHasModifiers, "Element %s does not have modifiers", element);
     return (XHasModifiers) element;
   }

   // Note: This method always returns `false` but I'd rather not remove it from our codebase since
   // if XProcessing adds package elements to their model I'd like to catch it here and fail early.
   public static boolean isPackage(XElement element) {
     // Currently, XProcessing doesn't represent package elements so this method always returns
     // false, but we check the state in Javac just to be sure. There's nothing to check in KSP since
     // there is no concept of package elements in KSP.
     if (getProcessingEnv(element).getBackend() == XProcessingEnv.Backend.JAVAC) {
       checkState(toJavac(element).getKind() != ElementKind.PACKAGE);
     }
     return false;
   }

   public static boolean isTypeParameter(XElement element) {
     return element instanceof XTypeParameterElement;
   }

   public static XTypeParameterElement asTypeParameter(XElement element) {
     return (XTypeParameterElement) element;
   }

   public static boolean isEnumEntry(XElement element) {
     return element instanceof XEnumEntry;
   }

   public static boolean isEnum(XElement element) {
     return element instanceof XEnumTypeElement;
   }

   public static boolean isExecutable(XElement element) {
     return isConstructor(element) || isMethod(element);
   }

   public static XExecutableElement asExecutable(XElement element) {
     checkState(isExecutable(element));
     return (XExecutableElement) element;
   }

   public static XTypeElement asTypeElement(XElement element) {
     checkState(isTypeElement(element));
     return (XTypeElement) element;
   }

   // TODO(bcorso): Rename this and the XElementKt.isMethodParameter to isExecutableParameter.
   public static XExecutableParameterElement asMethodParameter(XElement element) {
     checkState(isMethodParameter(element));
     return (XExecutableParameterElement) element;
   }

   public static XFieldElement asField(XElement element) {
     checkState(isField(element));
     return (XFieldElement) element;
   }

   public static XEnumEntry asEnumEntry(XElement element) {
     return (XEnumEntry) element;
   }

   public static XVariableElement asVariable(XElement element) {
     checkState(isVariableElement(element));
     return (XVariableElement) element;
   }

   public static XConstructorElement asConstructor(XElement element) {
     checkState(isConstructor(element));
     return (XConstructorElement) element;
   }

   public static XMethodElement asMethod(XElement element) {
     checkState(isMethod(element));
     return (XMethodElement) element;
   }

   public static ImmutableSet<XAnnotation> getAnnotatedAnnotations(
       XAnnotated annotated, ClassName annotationName) {
     return annotated.getAllAnnotations().stream()
         .filter(annotation -> annotation.getType().getTypeElement().hasAnnotation(annotationName))
         .collect(toImmutableSet());
   }

   /** Returns {@code true} if {@code annotated} is annotated with any of the given annotations. */
   public static boolean hasAnyAnnotation(XAnnotated annotated, ClassName... annotations) {
     return hasAnyAnnotation(annotated, ImmutableSet.copyOf(annotations));
   }

   /** Returns {@code true} if {@code annotated} is annotated with any of the given annotations. */
   public static boolean hasAnyAnnotation(XAnnotated annotated, Collection<ClassName> annotations) {
     return annotations.stream().anyMatch(annotated::hasAnnotation);
   }

   /**
    * Returns any annotation from {@code annotations} that annotates {@code annotated} or else {@code
    * Optional.empty()}.
    */
   public static Optional<XAnnotation> getAnyAnnotation(
       XAnnotated annotated, ClassName... annotations) {
     return getAnyAnnotation(annotated, ImmutableSet.copyOf(annotations));
   }

   /**
    * Returns any annotation from {@code annotations} that annotates {@code annotated} or else {@code
    * Optional.empty()}.
    */
   public static Optional<XAnnotation> getAnyAnnotation(
       XAnnotated annotated, Collection<ClassName> annotations) {
     return annotations.stream()
         .filter(annotated::hasAnnotation)
         .map(annotated::getAnnotation)
         .findFirst();
   }

   /** Returns all annotations from {@code annotations} that annotate {@code annotated}. */
   public static ImmutableSet<XAnnotation> getAllAnnotations(
       XAnnotated annotated, Collection<ClassName> annotations) {
     return annotations.stream()
         .filter(annotated::hasAnnotation)
         .map(annotated::getAnnotation)
         .collect(toImmutableSet());
   }

   /**
    * Returns the field descriptor of the given {@code element}.
    *
    * <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
    *
    * <p>For reference, see the <a
    * href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.2">JVM
    * specification, section 4.3.2</a>.
    */
   public static String getFieldDescriptor(XFieldElement element) {
     return getFieldDescriptor(toJavac(element));
   }

   /**
    * Returns the field descriptor of the given {@code element}.
    *
    * <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
    *
    * <p>For reference, see the <a
    * href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.2">JVM
    * specification, section 4.3.2</a>.
    */
   public static String getFieldDescriptor(VariableElement element) {
     return element.getSimpleName() + ":" + getDescriptor(element.asType());
   }

   /**
    * Returns the method descriptor of the given {@code element}.
    *
    * <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
    *
    * <p>For reference, see the <a
    * href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.3">JVM
    * specification, section 4.3.3</a>.
    */
   // TODO(bcorso): Expose getMethodDescriptor() method in XProcessing instead.
   public static String getMethodDescriptor(XMethodElement element) {
     return getMethodDescriptor(toJavac(element));
   }

   /**
    * Returns the method descriptor of the given {@code element}.
    *
    * <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
    *
    * <p>For reference, see the <a
    * href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.3">JVM
    * specification, section 4.3.3</a>.
    */
   public static String getMethodDescriptor(ExecutableElement element) {
     return element.getSimpleName() + getDescriptor(element.asType());
   }

   private static String getDescriptor(TypeMirror type) {
     return type.accept(JVM_DESCRIPTOR_TYPE_VISITOR, null);
   }

   private static final SimpleTypeVisitor8<String, Void> JVM_DESCRIPTOR_TYPE_VISITOR =
       new SimpleTypeVisitor8<String, Void>() {

         @Override
         public String visitArray(ArrayType arrayType, Void v) {
           return "[" + getDescriptor(arrayType.getComponentType());
         }

         @Override
         public String visitDeclared(DeclaredType declaredType, Void v) {
           return "L" + getInternalName(declaredType.asElement()) + ";";
         }

         @Override
         public String visitError(ErrorType errorType, Void v) {
           // For descriptor generating purposes we don't need a fully modeled type since we are
           // only interested in obtaining the class name in its "internal form".
           return visitDeclared(errorType, v);
         }

         @Override
         public String visitExecutable(ExecutableType executableType, Void v) {
           String parameterDescriptors =
               executableType.getParameterTypes().stream()
                   .map(XElements::getDescriptor)
                   .collect(joining());
           String returnDescriptor = getDescriptor(executableType.getReturnType());
           return "(" + parameterDescriptors + ")" + returnDescriptor;
         }

         @Override
         public String visitIntersection(IntersectionType intersectionType, Void v) {
           // For a type variable with multiple bounds: "the erasure of a type variable is determined
           // by the first type in its bound" - JVM Spec Sec 4.4
           return getDescriptor(intersectionType.getBounds().get(0));
         }

         @Override
         public String visitNoType(NoType noType, Void v) {
           return "V";
         }

         @Override
         public String visitPrimitive(PrimitiveType primitiveType, Void v) {
           switch (primitiveType.getKind()) {
             case BOOLEAN:
               return "Z";
             case BYTE:
               return "B";
             case SHORT:
               return "S";
             case INT:
               return "I";
             case LONG:
               return "J";
             case CHAR:
               return "C";
             case FLOAT:
               return "F";
             case DOUBLE:
               return "D";
             default:
               throw new IllegalArgumentException("Unknown primitive type.");
           }
         }

         @Override
         public String visitTypeVariable(TypeVariable typeVariable, Void v) {
           // The erasure of a type variable is the erasure of its leftmost bound. - JVM Spec Sec 4.6
           return getDescriptor(typeVariable.getUpperBound());
         }

         @Override
         public String defaultAction(TypeMirror typeMirror, Void v) {
           throw new IllegalArgumentException("Unsupported type: " + typeMirror);
         }

         @Override
         public String visitWildcard(WildcardType wildcardType, Void v) {
           return "";
         }

         /**
          * Returns the name of this element in its "internal form".
          *
          * <p>For reference, see the <a
          * href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2">JVM
          * specification, section 4.2</a>.
          */
         private String getInternalName(Element element) {
           try {
             TypeElement typeElement = MoreElements.asType(element);
             switch (typeElement.getNestingKind()) {
               case TOP_LEVEL:
                 return typeElement.getQualifiedName().toString().replace('.', '/');
               case MEMBER:
                 return getInternalName(typeElement.getEnclosingElement())
                     + "$"
                     + typeElement.getSimpleName();
               default:
                 throw new IllegalArgumentException("Unsupported nesting kind.");
             }
           } catch (IllegalArgumentException e) {
             // Not a TypeElement, try something else...
           }

           if (element instanceof QualifiedNameable) {
             QualifiedNameable qualifiedNameElement = (QualifiedNameable) element;
             return qualifiedNameElement.getQualifiedName().toString().replace('.', '/');
           }

           return element.getSimpleName().toString();
         }
       };

   private XElements() {}
 }
	/*
	* Copyright (C) 2021 The Dagger Authors.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package dagger.internal.codegen.xprocessing;

	import static androidx.room.compiler.processing.XElementKt.isConstructor;
	import static androidx.room.compiler.processing.XElementKt.isField;
	import static androidx.room.compiler.processing.XElementKt.isMethod;
	import static androidx.room.compiler.processing.XElementKt.isMethodParameter;
	import static androidx.room.compiler.processing.XElementKt.isTypeElement;
	import static androidx.room.compiler.processing.XElementKt.isVariableElement;
	import static androidx.room.compiler.processing.compat.XConverters.getProcessingEnv;
	import static androidx.room.compiler.processing.compat.XConverters.toJavac;
	import static com.google.common.base.Preconditions.checkArgument;
	import static com.google.common.base.Preconditions.checkState;
	import static dagger.internal.codegen.extension.DaggerStreams.toImmutableSet;
	import static java.util.stream.Collectors.joining;

	import androidx.room.compiler.processing.XAnnotated;
	import androidx.room.compiler.processing.XAnnotation;
	import androidx.room.compiler.processing.XConstructorElement;
	import androidx.room.compiler.processing.XElement;
	import androidx.room.compiler.processing.XEnumEntry;
	import androidx.room.compiler.processing.XEnumTypeElement;
	import androidx.room.compiler.processing.XExecutableElement;
	import androidx.room.compiler.processing.XExecutableParameterElement;
	import androidx.room.compiler.processing.XFieldElement;
	import androidx.room.compiler.processing.XHasModifiers;
	import androidx.room.compiler.processing.XMemberContainer;
	import androidx.room.compiler.processing.XMethodElement;
	import androidx.room.compiler.processing.XProcessingEnv;
	import androidx.room.compiler.processing.XTypeElement;
	import androidx.room.compiler.processing.XTypeParameterElement;
	import androidx.room.compiler.processing.XVariableElement;
	import com.google.auto.common.MoreElements;
	import com.google.common.collect.ImmutableSet;
	import com.squareup.javapoet.ClassName;
	import java.util.Collection;
	import java.util.Optional;
	import javax.lang.model.element.Element;
	import javax.lang.model.element.ElementKind;
	import javax.lang.model.element.ExecutableElement;
	import javax.lang.model.element.QualifiedNameable;
	import javax.lang.model.element.TypeElement;
	import javax.lang.model.element.VariableElement;
	import javax.lang.model.type.ArrayType;
	import javax.lang.model.type.DeclaredType;
	import javax.lang.model.type.ErrorType;
	import javax.lang.model.type.ExecutableType;
	import javax.lang.model.type.IntersectionType;
	import javax.lang.model.type.NoType;
	import javax.lang.model.type.PrimitiveType;
	import javax.lang.model.type.TypeMirror;
	import javax.lang.model.type.TypeVariable;
	import javax.lang.model.type.WildcardType;
	import javax.lang.model.util.SimpleTypeVisitor8;

	// TODO(bcorso): Consider moving these methods into XProcessing library.
	/** A utility class for {@link XElement} helper methods. */
	public final class XElements {

	// TODO(bcorso): Replace usages with getJvmName() once it exists.
	/** Returns the simple name of the member container. */
	public static String getSimpleName(XMemberContainer memberContainer) {
	return memberContainer.getClassName().simpleName();
	}

	/** Returns the simple name of the element. */
	public static String getSimpleName(XElement element) {
	if (isTypeElement(element)) {
	return asTypeElement(element)
	.getName(); // SUPPRESS_GET_NAME_CHECK: This uses java simple name implementation under
	// the hood.
	} else if (isVariableElement(element)) {
	return asVariable(element).getName(); // SUPPRESS_GET_NAME_CHECK
	} else if (isEnumEntry(element)) {
	return asEnumEntry(element).getName(); // SUPPRESS_GET_NAME_CHECK
	} else if (isMethod(element)) {
	return asMethod(element).getJvmName();
	} else if (isConstructor(element)) {
	return "<init>";
	}
	throw new AssertionError("No simple name for: " + element);
	}

	/**
	* Returns the closest enclosing element that is a {@link XTypeElement} or throws an {@link
	* IllegalStateException} if one doesn't exists.
	*/
	public static XTypeElement closestEnclosingTypeElement(XElement element) {
	return optionalClosestEnclosingTypeElement(element)
	.orElseThrow(() -> new IllegalStateException("No enclosing TypeElement for: " + element));
	}

	/**
	* Returns {@code true} if {@code encloser} is equal to or transitively encloses {@code enclosed}.
	*/
	public static boolean transitivelyEncloses(XElement encloser, XElement enclosed) {
	XElement current = enclosed;
	while (current != null) {
	if (current.equals(encloser)) {
	return true;
	}
	current = current.getEnclosingElement();
	}
	return false;
	}

	private static Optional<XTypeElement> optionalClosestEnclosingTypeElement(XElement element) {
	if (isTypeElement(element)) {
	return Optional.of(asTypeElement(element));
	} else if (isConstructor(element)) {
	return Optional.of(asConstructor(element).getEnclosingElement());
	} else if (isMethod(element)) {
	return optionalClosestEnclosingTypeElement(asMethod(element).getEnclosingElement());
	} else if (isField(element)) {
	return optionalClosestEnclosingTypeElement(asField(element).getEnclosingElement());
	} else if (isMethodParameter(element)) {
	return optionalClosestEnclosingTypeElement(asMethodParameter(element).getEnclosingElement());
	}
	return Optional.empty();
	}

	public static boolean isAbstract(XElement element) {
	return asHasModifiers(element).isAbstract();
	}

	public static boolean isPublic(XElement element) {
	return asHasModifiers(element).isPublic();
	}

	public static boolean isPrivate(XElement element) {
	return asHasModifiers(element).isPrivate();
	}

	public static boolean isStatic(XElement element) {
	return asHasModifiers(element).isStatic();
	}

	// TODO(bcorso): Ideally we would modify XElement to extend XHasModifiers to prevent possible
	// runtime exceptions if the element does not extend XHasModifiers. However, for Dagger's purpose
	// all usages should be on elements that do extend XHasModifiers, so generalizing this for
	// XProcessing is probably overkill for now.
	private static XHasModifiers asHasModifiers(XElement element) {
	// In javac, Element implements HasModifiers but in XProcessing XElement does not.
	// Currently, the elements that do not extend XHasModifiers are XMemberContainer, XEnumEntry,
	// XVariableElement. Though most instances of XMemberContainer will extend XHasModifiers through
	// XTypeElement instead.
	checkArgument(element instanceof XHasModifiers, "Element %s does not have modifiers", element);
	return (XHasModifiers) element;
	}

	// Note: This method always returns `false` but I'd rather not remove it from our codebase since
	// if XProcessing adds package elements to their model I'd like to catch it here and fail early.
	public static boolean isPackage(XElement element) {
	// Currently, XProcessing doesn't represent package elements so this method always returns
	// false, but we check the state in Javac just to be sure. There's nothing to check in KSP since
	// there is no concept of package elements in KSP.
	if (getProcessingEnv(element).getBackend() == XProcessingEnv.Backend.JAVAC) {
	checkState(toJavac(element).getKind() != ElementKind.PACKAGE);
	}
	return false;
	}

	public static boolean isTypeParameter(XElement element) {
	return element instanceof XTypeParameterElement;
	}

	public static XTypeParameterElement asTypeParameter(XElement element) {
	return (XTypeParameterElement) element;
	}

	public static boolean isEnumEntry(XElement element) {
	return element instanceof XEnumEntry;
	}

	public static boolean isEnum(XElement element) {
	return element instanceof XEnumTypeElement;
	}

	public static boolean isExecutable(XElement element) {
	return isConstructor(element) \|\| isMethod(element);
	}

	public static XExecutableElement asExecutable(XElement element) {
	checkState(isExecutable(element));
	return (XExecutableElement) element;
	}

	public static XTypeElement asTypeElement(XElement element) {
	checkState(isTypeElement(element));
	return (XTypeElement) element;
	}

	// TODO(bcorso): Rename this and the XElementKt.isMethodParameter to isExecutableParameter.
	public static XExecutableParameterElement asMethodParameter(XElement element) {
	checkState(isMethodParameter(element));
	return (XExecutableParameterElement) element;
	}

	public static XFieldElement asField(XElement element) {
	checkState(isField(element));
	return (XFieldElement) element;
	}

	public static XEnumEntry asEnumEntry(XElement element) {
	return (XEnumEntry) element;
	}

	public static XVariableElement asVariable(XElement element) {
	checkState(isVariableElement(element));
	return (XVariableElement) element;
	}

	public static XConstructorElement asConstructor(XElement element) {
	checkState(isConstructor(element));
	return (XConstructorElement) element;
	}

	public static XMethodElement asMethod(XElement element) {
	checkState(isMethod(element));
	return (XMethodElement) element;
	}

	public static ImmutableSet<XAnnotation> getAnnotatedAnnotations(
	XAnnotated annotated, ClassName annotationName) {
	return annotated.getAllAnnotations().stream()
	.filter(annotation -> annotation.getType().getTypeElement().hasAnnotation(annotationName))
	.collect(toImmutableSet());
	}

	/** Returns {@code true} if {@code annotated} is annotated with any of the given annotations. */
	public static boolean hasAnyAnnotation(XAnnotated annotated, ClassName... annotations) {
	return hasAnyAnnotation(annotated, ImmutableSet.copyOf(annotations));
	}

	/** Returns {@code true} if {@code annotated} is annotated with any of the given annotations. */
	public static boolean hasAnyAnnotation(XAnnotated annotated, Collection<ClassName> annotations) {
	return annotations.stream().anyMatch(annotated::hasAnnotation);
	}

	/**
	* Returns any annotation from {@code annotations} that annotates {@code annotated} or else {@code
	* Optional.empty()}.
	*/
	public static Optional<XAnnotation> getAnyAnnotation(
	XAnnotated annotated, ClassName... annotations) {
	return getAnyAnnotation(annotated, ImmutableSet.copyOf(annotations));
	}

	/**
	* Returns any annotation from {@code annotations} that annotates {@code annotated} or else {@code
	* Optional.empty()}.
	*/
	public static Optional<XAnnotation> getAnyAnnotation(
	XAnnotated annotated, Collection<ClassName> annotations) {
	return annotations.stream()
	.filter(annotated::hasAnnotation)
	.map(annotated::getAnnotation)
	.findFirst();
	}

	/** Returns all annotations from {@code annotations} that annotate {@code annotated}. */
	public static ImmutableSet<XAnnotation> getAllAnnotations(
	XAnnotated annotated, Collection<ClassName> annotations) {
	return annotations.stream()
	.filter(annotated::hasAnnotation)
	.map(annotated::getAnnotation)
	.collect(toImmutableSet());
	}

	/**
	* Returns the field descriptor of the given {@code element}.
	*
	* <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
	*
	* <p>For reference, see the <a
	* href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.2">JVM
	* specification, section 4.3.2</a>.
	*/
	public static String getFieldDescriptor(XFieldElement element) {
	return getFieldDescriptor(toJavac(element));
	}

	/**
	* Returns the field descriptor of the given {@code element}.
	*
	* <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
	*
	* <p>For reference, see the <a
	* href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.2">JVM
	* specification, section 4.3.2</a>.
	*/
	public static String getFieldDescriptor(VariableElement element) {
	return element.getSimpleName() + ":" + getDescriptor(element.asType());
	}

	/**
	* Returns the method descriptor of the given {@code element}.
	*
	* <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
	*
	* <p>For reference, see the <a
	* href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.3">JVM
	* specification, section 4.3.3</a>.
	*/
	// TODO(bcorso): Expose getMethodDescriptor() method in XProcessing instead.
	public static String getMethodDescriptor(XMethodElement element) {
	return getMethodDescriptor(toJavac(element));
	}

	/**
	* Returns the method descriptor of the given {@code element}.
	*
	* <p>This is useful for matching Kotlin Metadata JVM Signatures with elements from the AST.
	*
	* <p>For reference, see the <a
	* href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.3">JVM
	* specification, section 4.3.3</a>.
	*/
	public static String getMethodDescriptor(ExecutableElement element) {
	return element.getSimpleName() + getDescriptor(element.asType());
	}

	private static String getDescriptor(TypeMirror type) {
	return type.accept(JVM_DESCRIPTOR_TYPE_VISITOR, null);
	}

	private static final SimpleTypeVisitor8<String, Void> JVM_DESCRIPTOR_TYPE_VISITOR =
	new SimpleTypeVisitor8<String, Void>() {

	@Override
	public String visitArray(ArrayType arrayType, Void v) {
	return "[" + getDescriptor(arrayType.getComponentType());
	}

	@Override
	public String visitDeclared(DeclaredType declaredType, Void v) {
	return "L" + getInternalName(declaredType.asElement()) + ";";
	}

	@Override
	public String visitError(ErrorType errorType, Void v) {
	// For descriptor generating purposes we don't need a fully modeled type since we are
	// only interested in obtaining the class name in its "internal form".
	return visitDeclared(errorType, v);
	}

	@Override
	public String visitExecutable(ExecutableType executableType, Void v) {
	String parameterDescriptors =
	executableType.getParameterTypes().stream()
	.map(XElements::getDescriptor)
	.collect(joining());
	String returnDescriptor = getDescriptor(executableType.getReturnType());
	return "(" + parameterDescriptors + ")" + returnDescriptor;
	}

	@Override
	public String visitIntersection(IntersectionType intersectionType, Void v) {
	// For a type variable with multiple bounds: "the erasure of a type variable is determined
	// by the first type in its bound" - JVM Spec Sec 4.4
	return getDescriptor(intersectionType.getBounds().get(0));
	}

	@Override
	public String visitNoType(NoType noType, Void v) {
	return "V";
	}

	@Override
	public String visitPrimitive(PrimitiveType primitiveType, Void v) {
	switch (primitiveType.getKind()) {
	case BOOLEAN:
	return "Z";
	case BYTE:
	return "B";
	case SHORT:
	return "S";
	case INT:
	return "I";
	case LONG:
	return "J";
	case CHAR:
	return "C";
	case FLOAT:
	return "F";
	case DOUBLE:
	return "D";
	default:
	throw new IllegalArgumentException("Unknown primitive type.");
	}
	}

	@Override
	public String visitTypeVariable(TypeVariable typeVariable, Void v) {
	// The erasure of a type variable is the erasure of its leftmost bound. - JVM Spec Sec 4.6
	return getDescriptor(typeVariable.getUpperBound());
	}

	@Override
	public String defaultAction(TypeMirror typeMirror, Void v) {
	throw new IllegalArgumentException("Unsupported type: " + typeMirror);
	}

	@Override
	public String visitWildcard(WildcardType wildcardType, Void v) {
	return "";
	}

	/**
	* Returns the name of this element in its "internal form".
	*
	* <p>For reference, see the <a
	* href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2">JVM
	* specification, section 4.2</a>.
	*/
	private String getInternalName(Element element) {
	try {
	TypeElement typeElement = MoreElements.asType(element);
	switch (typeElement.getNestingKind()) {
	case TOP_LEVEL:
	return typeElement.getQualifiedName().toString().replace('.', '/');
	case MEMBER:
	return getInternalName(typeElement.getEnclosingElement())
	+ "$"
	+ typeElement.getSimpleName();
	default:
	throw new IllegalArgumentException("Unsupported nesting kind.");
	}
	} catch (IllegalArgumentException e) {
	// Not a TypeElement, try something else...
	}

	if (element instanceof QualifiedNameable) {
	QualifiedNameable qualifiedNameElement = (QualifiedNameable) element;
	return qualifiedNameElement.getQualifiedName().toString().replace('.', '/');
	}

	return element.getSimpleName().toString();
	}
	};

	private XElements() {}
	}