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qwen/nodejs/node_modules/eslint/lib/rules/no-unreachable.js

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+/**
+ * @fileoverview Checks for unreachable code due to return, throws, break, and continue.
+ * @author Joel Feenstra
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/**
+ * @typedef {Object} ConstructorInfo
+ * @property {ConstructorInfo | null} upper Info about the constructor that encloses this constructor.
+ * @property {boolean} hasSuperCall The flag about having `super()` expressions.
+ */
+
+/**
+ * Checks whether or not a given variable declarator has the initializer.
+ * @param {ASTNode} node A VariableDeclarator node to check.
+ * @returns {boolean} `true` if the node has the initializer.
+ */
+function isInitialized(node) {
+    return Boolean(node.init);
+}
+
+/**
+ * Checks all segments in a set and returns true if all are unreachable.
+ * @param {Set<CodePathSegment>} segments The segments to check.
+ * @returns {boolean} True if all segments are unreachable; false otherwise.
+ */
+function areAllSegmentsUnreachable(segments) {
+
+    for (const segment of segments) {
+        if (segment.reachable) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * The class to distinguish consecutive unreachable statements.
+ */
+class ConsecutiveRange {
+    constructor(sourceCode) {
+        this.sourceCode = sourceCode;
+        this.startNode = null;
+        this.endNode = null;
+    }
+
+    /**
+     * The location object of this range.
+     * @type {Object}
+     */
+    get location() {
+        return {
+            start: this.startNode.loc.start,
+            end: this.endNode.loc.end
+        };
+    }
+
+    /**
+     * `true` if this range is empty.
+     * @type {boolean}
+     */
+    get isEmpty() {
+        return !(this.startNode && this.endNode);
+    }
+
+    /**
+     * Checks whether the given node is inside of this range.
+     * @param {ASTNode|Token} node The node to check.
+     * @returns {boolean} `true` if the node is inside of this range.
+     */
+    contains(node) {
+        return (
+            node.range[0] >= this.startNode.range[0] &&
+            node.range[1] <= this.endNode.range[1]
+        );
+    }
+
+    /**
+     * Checks whether the given node is consecutive to this range.
+     * @param {ASTNode} node The node to check.
+     * @returns {boolean} `true` if the node is consecutive to this range.
+     */
+    isConsecutive(node) {
+        return this.contains(this.sourceCode.getTokenBefore(node));
+    }
+
+    /**
+     * Merges the given node to this range.
+     * @param {ASTNode} node The node to merge.
+     * @returns {void}
+     */
+    merge(node) {
+        this.endNode = node;
+    }
+
+    /**
+     * Resets this range by the given node or null.
+     * @param {ASTNode|null} node The node to reset, or null.
+     * @returns {void}
+     */
+    reset(node) {
+        this.startNode = this.endNode = node;
+    }
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "problem",
+
+        docs: {
+            description: "Disallow unreachable code after `return`, `throw`, `continue`, and `break` statements",
+            recommended: true,
+            url: "https://eslint.org/docs/latest/rules/no-unreachable"
+        },
+
+        schema: [],
+
+        messages: {
+            unreachableCode: "Unreachable code."
+        }
+    },
+
+    create(context) {
+
+        /** @type {ConstructorInfo | null} */
+        let constructorInfo = null;
+
+        /** @type {ConsecutiveRange} */
+        const range = new ConsecutiveRange(context.sourceCode);
+
+        /** @type {Array<Set<CodePathSegment>>} */
+        const codePathSegments = [];
+
+        /** @type {Set<CodePathSegment>} */
+        let currentCodePathSegments = new Set();
+
+        /**
+         * Reports a given node if it's unreachable.
+         * @param {ASTNode} node A statement node to report.
+         * @returns {void}
+         */
+        function reportIfUnreachable(node) {
+            let nextNode = null;
+
+            if (node && (node.type === "PropertyDefinition" || areAllSegmentsUnreachable(currentCodePathSegments))) {
+
+                // Store this statement to distinguish consecutive statements.
+                if (range.isEmpty) {
+                    range.reset(node);
+                    return;
+                }
+
+                // Skip if this statement is inside of the current range.
+                if (range.contains(node)) {
+                    return;
+                }
+
+                // Merge if this statement is consecutive to the current range.
+                if (range.isConsecutive(node)) {
+                    range.merge(node);
+                    return;
+                }
+
+                nextNode = node;
+            }
+
+            /*
+             * Report the current range since this statement is reachable or is
+             * not consecutive to the current range.
+             */
+            if (!range.isEmpty) {
+                context.report({
+                    messageId: "unreachableCode",
+                    loc: range.location,
+                    node: range.startNode
+                });
+            }
+
+            // Update the current range.
+            range.reset(nextNode);
+        }
+
+        return {
+
+            // Manages the current code path.
+            onCodePathStart() {
+                codePathSegments.push(currentCodePathSegments);
+                currentCodePathSegments = new Set();
+            },
+
+            onCodePathEnd() {
+                currentCodePathSegments = codePathSegments.pop();
+            },
+
+            onUnreachableCodePathSegmentStart(segment) {
+                currentCodePathSegments.add(segment);
+            },
+
+            onUnreachableCodePathSegmentEnd(segment) {
+                currentCodePathSegments.delete(segment);
+            },
+
+            onCodePathSegmentEnd(segment) {
+                currentCodePathSegments.delete(segment);
+            },
+
+            onCodePathSegmentStart(segment) {
+                currentCodePathSegments.add(segment);
+            },
+
+            // Registers for all statement nodes (excludes FunctionDeclaration).
+            BlockStatement: reportIfUnreachable,
+            BreakStatement: reportIfUnreachable,
+            ClassDeclaration: reportIfUnreachable,
+            ContinueStatement: reportIfUnreachable,
+            DebuggerStatement: reportIfUnreachable,
+            DoWhileStatement: reportIfUnreachable,
+            ExpressionStatement: reportIfUnreachable,
+            ForInStatement: reportIfUnreachable,
+            ForOfStatement: reportIfUnreachable,
+            ForStatement: reportIfUnreachable,
+            IfStatement: reportIfUnreachable,
+            ImportDeclaration: reportIfUnreachable,
+            LabeledStatement: reportIfUnreachable,
+            ReturnStatement: reportIfUnreachable,
+            SwitchStatement: reportIfUnreachable,
+            ThrowStatement: reportIfUnreachable,
+            TryStatement: reportIfUnreachable,
+
+            VariableDeclaration(node) {
+                if (node.kind !== "var" || node.declarations.some(isInitialized)) {
+                    reportIfUnreachable(node);
+                }
+            },
+
+            WhileStatement: reportIfUnreachable,
+            WithStatement: reportIfUnreachable,
+            ExportNamedDeclaration: reportIfUnreachable,
+            ExportDefaultDeclaration: reportIfUnreachable,
+            ExportAllDeclaration: reportIfUnreachable,
+
+            "Program:exit"() {
+                reportIfUnreachable();
+            },
+
+            /*
+             * Instance fields defined in a subclass are never created if the constructor of the subclass
+             * doesn't call `super()`, so their definitions are unreachable code.
+             */
+            "MethodDefinition[kind='constructor']"() {
+                constructorInfo = {
+                    upper: constructorInfo,
+                    hasSuperCall: false
+                };
+            },
+            "MethodDefinition[kind='constructor']:exit"(node) {
+                const { hasSuperCall } = constructorInfo;
+
+                constructorInfo = constructorInfo.upper;
+
+                // skip typescript constructors without the body
+                if (!node.value.body) {
+                    return;
+                }
+
+                const classDefinition = node.parent.parent;
+
+                if (classDefinition.superClass && !hasSuperCall) {
+                    for (const element of classDefinition.body.body) {
+                        if (element.type === "PropertyDefinition" && !element.static) {
+                            reportIfUnreachable(element);
+                        }
+                    }
+                }
+            },
+            "CallExpression > Super.callee"() {
+                if (constructorInfo) {
+                    constructorInfo.hasSuperCall = true;
+                }
+            }
+        };
+    }
+};