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package com.signalfx.shaded.checkerframework.framework.qual;
import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* A meta-annotation that indicates that an annotation R is a precondition annotation, i.e., R is a
* type-specialized version of {@link RequiresQualifier}. The value {@code qualifier} that is
* necessary for a precondition specified with {@link RequiresQualifier} is specified here with the
* value {@code qualifier}.
*
* The annotation R that is meta-annotated as {@link PreconditionAnnotation} must have an element
* called {@code value} that is an array of {@code String}s of the same format and with the same
* meaning as the value {@code expression} in {@link RequiresQualifier}.
*
*
The established precondition P has type specified by the {@code qualifier} field of this
* annotation. If the annotation R has elements annotated by {@link QualifierArgument}, their values
* are copied to the arguments (elements) of annotation P with the same names. Different element
* names may be used in R and P, if a {@link QualifierArgument} in R gives the name of the
* corresponding element in P.
*
*
For example, the following code declares a precondition annotation for the {@link
* com.signalfx.shaded.checkerframework.common.value.qual.MinLen} qualifier:
*
*
* {@literal @}PreconditionAnnotation(qualifier = MinLen.class)
* {@literal @}Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
* public {@literal @}interface RequiresMinLen {
* String[] value();
* {@literal @}QualifierArgument("value")
* int targetValue() default 0;
*
*
* The {@code value} element holds the expressions to which the qualifier applies and {@code
* targetValue} holds the value for the {@code value} argument of {@link
* com.signalfx.shaded.checkerframework.common.value.qual.MinLen}.
*
* The following code then uses the annotation on a method that requires {@code field} to be
* {@code @MinLen(2)} upon entry.
*
*
* {@literal @}RequiresMinLen(value = "field", targetValue = 2")
* public char getThirdCharacter() {
* return field.charAt(2);
* }
*
*
* @see RequiresQualifier
* @see QualifierArgument
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.ANNOTATION_TYPE})
public @interface PreconditionAnnotation {
/** The qualifier that must be established as a precondition. */
Class qualifier();
}