package org.checkerframework.checker.units.qual;
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;
import org.checkerframework.framework.qual.PolymorphicQualifier;
/**
* A polymorphic qualifier for the units-of-measure type system implemented by the Units Checker.
*
* <p>Any method written using @PolyUnit conceptually has many versions: in each one, every instance
* of @PolyUnit has been replaced by a different unit qualifier such as @kg (kilograms) or @h
* (hours).
*
* <p>The following example shows how method {@code triplePolyUnit} can be used to process either
* meters or seconds:
*
* <pre><code>
* {@literal @}PolyUnit int triplePolyUnit(@PolyUnit int amount) {
* return 3*amount;
* }
*
* void testPolyUnit() {
* {@literal @}m int m1 = 7 * UnitsTools.m;
* {@literal @}m int m2 = triplePolyUnit(m1);
*
* {@literal @}s int sec1 = 7 * UnitsTools.s;
* {@literal @}s int sec2 = triplePolyUnit(sec1);
*
* //:: error: (assignment.type.incompatible)
* {@literal @}s int sec3 = triplePolyUnit(m1);
* }
* </code></pre>
*
* @checker_framework.manual #units-checker Units Checker
* @checker_framework.manual #qualifier-polymorphism Qualifier polymorphism
*/
@Documented
@PolymorphicQualifier(UnknownUnits.class)
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE_USE, ElementType.TYPE_PARAMETER})
public @interface PolyUnit {}