daniellansun commented on code in PR #2773: URL: https://github.com/apache/groovy/pull/2773#discussion_r3740600398
########## src/main/java/org/codehaus/groovy/classgen/InstanceofFlowBindings.java: ########## @@ -0,0 +1,249 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +package org.codehaus.groovy.classgen; + +import org.codehaus.groovy.ast.CodeVisitorSupport; +import org.codehaus.groovy.ast.expr.BinaryExpression; +import org.codehaus.groovy.ast.expr.BooleanExpression; +import org.codehaus.groovy.ast.expr.DeclarationExpression; +import org.codehaus.groovy.ast.expr.Expression; +import org.codehaus.groovy.ast.expr.NotExpression; +import org.codehaus.groovy.ast.expr.VariableExpression; +import org.codehaus.groovy.syntax.Types; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.LinkedHashSet; +import java.util.List; +import java.util.Set; + +/** + * Flow-sensitive analysis of JEP 394 {@code instanceof} pattern bindings + * (GROOVY-12242). + * <p> + * This is pure <em>semantic</em> analysis: given a boolean expression, which + * pattern variables are <em>definitely bound</em> when the expression is + * {@code true} versus {@code false}? (Same idea as compiler “flow info” / + * JEP 394 flow scoping — not a bytecode construct.) + * <ul> + * <li>{@link #of(Expression)} — true/false binding sets for a condition</li> + * <li>{@link #containsPattern(Expression)} — nested type-pattern presence + * (e.g. whether an expression statement needs CompileStack isolation)</li> + * </ul> + * Covered shapes: {@code e instanceof T t}, negation / {@code !instanceof}, + * {@code &&} (union of true bindings), {@code ||} (union of false bindings). + * Other shapes contribute nothing (conservative). + * <p> + * Consumers: + * <ul> + * <li>{@link VariableScopeVisitor} — declare names on the live path</li> + * <li>{@link org.codehaus.groovy.classgen.asm.InstanceofFlowSlotPublisher} — + * publish/hide CompileStack slots from these bindings</li> + * </ul> + * + * @see org.codehaus.groovy.classgen.asm.InstanceofFlowSlotPublisher + * @since 6.0.0 + */ +public final class InstanceofFlowBindings { + + private static final InstanceofFlowBindings EMPTY = + new InstanceofFlowBindings(List.of(), List.of()); + + private final List<VariableExpression> whenTrue; + private final List<VariableExpression> whenFalse; + + private InstanceofFlowBindings(final List<VariableExpression> whenTrue, + final List<VariableExpression> whenFalse) { + this.whenTrue = whenTrue; + this.whenFalse = whenFalse; + } + + /** + * Pattern variables that are definitely assigned when the analysed expression + * evaluates to {@code true}. + */ + public List<VariableExpression> whenTrue() { + return whenTrue; + } + + /** + * Pattern variables that are definitely assigned when the analysed expression + * evaluates to {@code false}. + */ + public List<VariableExpression> whenFalse() { + return whenFalse; + } + + /** Whether any pattern variable is bound on either path. */ + public boolean isEmpty() { + return whenTrue.isEmpty() && whenFalse.isEmpty(); + } + + /** + * Names of pattern variables bound when the expression is {@code true}. + */ + public Set<String> whenTrueNames() { + return names(whenTrue); + } + + /** + * Names of pattern variables bound when the expression is {@code false}. + */ + public Set<String> whenFalseNames() { + return names(whenFalse); + } + + /** + * All pattern-variable names appearing in either path (stable encounter order). + */ + public Set<String> allNames() { + if (isEmpty()) return Collections.emptySet(); + Set<String> names = new LinkedHashSet<>(whenTrue.size() + whenFalse.size()); + for (VariableExpression ve : whenTrue) names.add(ve.getName()); + for (VariableExpression ve : whenFalse) names.add(ve.getName()); + return names; + } Review Comment: Yes, exactly. Calling `names(whenTrue)` followed by `names(whenFalse)` would allocate *two* intermediate `LinkedHashSet` instances (one per call to `names()`), only to merge them into a third result set. The direct loop populates a single `LinkedHashSet` in one pass. The Javadoc for `allNames()` has been updated to document this rationale explicitly: ```java /** * All pattern-variable names appearing in either path (stable encounter order). * <p> * Implemented by iterating both lists directly rather than composing * {@link #whenTrueNames()} and {@link #whenFalseNames()}: that would * allocate two intermediate {@link Set} objects only to merge them into a * third, whereas the direct loop allocates only the result set. */ ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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