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package org.checkerframework.javacutil;
import com.sun.source.tree.BlockTree;
import com.sun.source.tree.CaseTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.util.TreeScanner;
import java.util.List;
import java.util.function.BiFunction;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A class that visits each result expression of a switch expression and calls {@link
* #visitSwitchResultExpression(ExpressionTree, Object)} on each result expression. The results of
* these method calls are combined using {@link #combineResults(Object, Object)}. Call {@link
* #scanSwitchExpression(Tree, Object)} to start scanning the switch expression.
*
* {@link FunctionalSwitchExpressionScanner} can be used to pass functions for to use for {@link
* #visitSwitchResultExpression(ExpressionTree, Object)} and {@link #combineResults(Object,
* Object)}.
*
* @param the type of the result of {@link #visitSwitchResultExpression(ExpressionTree, Object)}
* @param the type of the parameter to pass to {@link
* #visitSwitchResultExpression(ExpressionTree, Object)}
*/
public abstract class SwitchExpressionScanner extends TreeScanner {
/**
* This method is called for each result expression of the switch expression passed in {@link
* #scanSwitchExpression(Tree, Object)}.
*
* @param resultExpressionTree a result expression of the switch expression currently being
* scanned
* @param p a parameter
* @return the result of visiting the result expression
*/
protected abstract R visitSwitchResultExpression(ExpressionTree resultExpressionTree, P p);
/**
* This method combines the result of two calls to {@link
* #visitSwitchResultExpression(ExpressionTree, Object)} or {@code null} and the result of one
* call to {@link #visitSwitchResultExpression(ExpressionTree, Object)}.
*
* @param r1 a possibly null result returned by {@link
* #visitSwitchResultExpression(ExpressionTree, Object)}
* @param r2 a possibly null result returned by {@link
* #visitSwitchResultExpression(ExpressionTree, Object)}
* @return the combination of {@code r1} and {@code r2}
*/
protected abstract R combineResults(@Nullable R r1, @Nullable R r2);
/**
* Scans the given switch expression and calls {@link #visitSwitchResultExpression(ExpressionTree,
* Object)} on each result expression of the switch expression. {@link #combineResults(Object,
* Object)} is called to combine the results of visiting multiple switch result expressions.
*
* @param switchExpression a switch expression tree
* @param p the parameter to pass to {@link #visitSwitchResultExpression(ExpressionTree, Object)}
* @return the result of calling {@link #visitSwitchResultExpression(ExpressionTree, Object)} on
* each result expression of {@code switchExpression} and combining the results using {@link
* #combineResults(Object, Object)}
*/
public R scanSwitchExpression(Tree switchExpression, P p) {
assert switchExpression.getKind().name().equals("SWITCH_EXPRESSION");
List caseTrees = TreeUtils.switchExpressionTreeGetCases(switchExpression);
R result = null;
for (CaseTree caseTree : caseTrees) {
if (caseTree.getStatements() != null) {
// This case is a switch labeled statement group, so scan the statements for yield
// statements.
result = combineResults(result, yieldVisitor.scan(caseTree.getStatements(), p));
} else {
@SuppressWarnings(
"nullness:assignment") // caseTree.getStatements() == null, so the case has a body.
@NonNull Tree body = TreeUtils.caseTreeGetBody(caseTree);
// This case is a switch rule, so its body is either an expression, block, or throw.
// See https://docs.oracle.com/javase/specs/jls/se17/html/jls-15.html#jls-15.28.2.
if (body.getKind() == Kind.BLOCK) {
// Scan for yield statements.
result = combineResults(result, yieldVisitor.scan(((BlockTree) body).getStatements(), p));
} else if (body.getKind() != Kind.THROW) {
// The expression is the result expression.
ExpressionTree expressionTree = (ExpressionTree) body;
result = combineResults(result, visitSwitchResultExpression(expressionTree, p));
}
}
}
@SuppressWarnings(
"nullness:assignment" // switch expressions must have at least one case that results in a
// value, so {@code result} must be nonnull.
)
@NonNull R nonNullResult = result;
return nonNullResult;
}
/**
* A scanner that visits all the yield trees in a given tree and calls {@link
* #visitSwitchResultExpression(ExpressionTree, Object)} on the expression in the yield trees. It
* does not descend into switch expressions.
*/
protected YieldVisitor yieldVisitor = new YieldVisitor();
/**
* A scanner that visits all the yield trees in a given tree and calls {@link
* #visitSwitchResultExpression(ExpressionTree, Object)} on the expression in the yield trees. It
* does not descend into switch expressions.
*/
protected class YieldVisitor extends TreeScanner<@Nullable R, P> {
@Override
public @Nullable R scan(Tree tree, P p) {
if (tree == null) {
return null;
}
if (tree.getKind().name().equals("SWITCH_EXPRESSION")) {
// Don't scan nested switch expressions.
return null;
} else if (tree.getKind().name().equals("YIELD")) {
ExpressionTree value = TreeUtils.yieldTreeGetValue(tree);
return visitSwitchResultExpression(value, p);
}
return super.scan(tree, p);
}
@Override
public R reduce(R r1, R r2) {
return combineResults(r1, r2);
}
}
/**
* An implementation of {@link SwitchExpressionScanner} that uses functions passed to the
* constructor for {@link #visitSwitchResultExpression(ExpressionTree, Object)} and {@link
* #combineResults(Object, Object)}.
*
* @param the type result of {@link #visitSwitchResultExpression(ExpressionTree, Object)}
* @param the type of the parameter to pass to {@link
* #visitSwitchResultExpression(ExpressionTree, Object)}
*/
public static class FunctionalSwitchExpressionScanner
extends SwitchExpressionScanner {
/** The function to use for {@link #visitSwitchResultExpression(ExpressionTree, Object)}. */
private final BiFunction switchValueExpressionFunction;
/** The function to use for {@link #visitSwitchResultExpression(ExpressionTree, Object)}. */
private final BiFunction<@Nullable R1, @Nullable R1, R1> combineResultFunc;
/**
* Creates a {@link FunctionalSwitchExpressionScanner} that uses the given functions.
*
* @param switchValueExpressionFunc the function called on each switch result expression
* @param combineResultFunc the function used to combine the result of multiple calls to {@code
* switchValueExpressionFunc}
*/
public FunctionalSwitchExpressionScanner(
BiFunction switchValueExpressionFunc,
BiFunction<@Nullable R1, @Nullable R1, R1> combineResultFunc) {
this.switchValueExpressionFunction = switchValueExpressionFunc;
this.combineResultFunc = combineResultFunc;
}
@Override
protected R1 visitSwitchResultExpression(ExpressionTree resultExpressionTree, P1 p1) {
return switchValueExpressionFunction.apply(resultExpressionTree, p1);
}
@Override
protected R1 combineResults(@Nullable R1 r1, @Nullable R1 r2) {
return combineResultFunc.apply(r1, r2);
}
}
}