src/main/java/org/zwobble/couscous/transforms/DesugarForEachToFor.java


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package org.zwobble.couscous.transforms;

import org.zwobble.couscous.ast.*;
import org.zwobble.couscous.ast.visitors.NodeTransformer;
import org.zwobble.couscous.frontends.java.JavaTypes;
import org.zwobble.couscous.frontends.java.Scope;
import org.zwobble.couscous.types.Type;
import org.zwobble.couscous.types.Types;

import java.util.List;

import static org.zwobble.couscous.ast.LocalVariableDeclarationNode.localVariableDeclaration;
import static org.zwobble.couscous.ast.MethodCallNode.methodCall;
import static org.zwobble.couscous.ast.VariableReferenceNode.reference;
import static org.zwobble.couscous.types.BoundTypeParameter.boundTypeParameter;
import static org.zwobble.couscous.util.ExtraLists.cons;
import static org.zwobble.couscous.util.ExtraLists.list;

public class DesugarForEachToFor {
    public static NodeTransformer transformer() {
        Scope scope = Scope.create().temporaryPrefix("_couscous_desugar_foreach_to_for");
        return DesugarStatement.<ForEachNode>transformer(NodeTypes.FOR_EACH, node -> desugar(scope, node));
    }

    public static List<StatementNode> desugar(Scope scope, ForEachNode forEach) {
        Type elementType = forEach.getTarget().getType();
        ExpressionNode iteratorValue = methodCall(forEach.getIterable(), "iterator", list(), JavaTypes.iterator(elementType));
        LocalVariableDeclarationNode iterator = scope.temporaryVariable(iteratorValue);

        ExpressionNode hasNext = methodCall(reference(iterator), "hasNext", list(), Types.BOOLEAN);
        ExpressionNode next = methodCall(reference(iterator), "next", list(), boundTypeParameter(JavaTypes.ITERATOR_TYPE_PARAMETER, elementType));
        ForNode loop = new ForNode(
            list(iterator),
            hasNext,
            list(),
            cons(
                localVariableDeclaration(forEach.getTarget(), next),
                forEach.getStatements()
            )
        );

        return list(loop);
    }
}