SLTypes.java

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package com.oracle.truffle.sl.nodes;

import java.math.BigInteger;

import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.api.dsl.ImplicitCast;
import com.oracle.truffle.api.dsl.TypeCast;
import com.oracle.truffle.api.dsl.TypeCheck;
import com.oracle.truffle.api.dsl.TypeSystem;
import com.oracle.truffle.sl.SLLanguage;
import com.oracle.truffle.sl.runtime.SLFunction;
import com.oracle.truffle.sl.runtime.SLNull;

/**
 * The type system of SL, as explained in {@link SLLanguage}. Based on the {@link TypeSystem}
 * annotation, the Truffle DSL generates the subclass {@link SLTypesGen} with type test and type
 * conversion methods for all types. In this class, we only cover types where the automatically
 * generated ones would not be sufficient.
 */
@TypeSystem({long.class, BigInteger.class, boolean.class, String.class, SLFunction.class, SLNull.class})
public abstract class SLTypes {

    /**
     * Example of a manually specified type check that replaces the automatically generated type
     * check that the Truffle DSL would generate. For {@link SLNull}, we do not need an
     * {@code instanceof} check, because we know that there is only a {@link SLNull#SINGLETON
     * singleton} instance.
     */
    @TypeCheck(SLNull.class)
    public static boolean isSLNull(Object value) {
        return value == SLNull.SINGLETON;
    }

    /**
     * Example of a manually specified type cast that replaces the automatically generated type cast
     * that the Truffle DSL would generate. For {@link SLNull}, we do not need an actual cast,
     * because we know that there is only a {@link SLNull#SINGLETON singleton} instance.
     */
    @TypeCast(SLNull.class)
    public static SLNull asSLNull(Object value) {
        assert isSLNull(value);
        return SLNull.SINGLETON;
    }

    /**
     * Informs the Truffle DSL that a primitive {@code long} value can be used in all
     * specializations where a {@link BigInteger} is expected. This models the semantic of SL: It
     * only has an arbitrary precision Number type (implemented as {@link BigInteger}, and
     * {@code long} is only used as a performance optimization to avoid the costly
     * {@link BigInteger} arithmetic for values that fit into a 64-bit primitive value.
     */
    @ImplicitCast
    @TruffleBoundary
    public static BigInteger castBigInteger(long value) {
        return BigInteger.valueOf(value);
    }
}