prefer-string-slice: Improve argument type detection (#1664)

Author: fisker

rules/prefer-string-slice.js

@@ -1,6 +1,7 @@
 'use strict';
 const eslintTemplateVisitor = require('eslint-template-visitor');
 const {getParenthesizedText} = require('./utils/parentheses.js');
+const isNumber = require('./utils/is-number.js');
 
 const MESSAGE_ID_SUBSTR = 'substr';
 const MESSAGE_ID_SUBSTRING = 'substring';
@@ -38,8 +39,6 @@ const isLengthProperty = node => (
 	&& node.property.name === 'length'
 );
 
-const isLikelyNumeric = node => isLiteralNumber(node) || isLengthProperty(node);
-
 /** @param {import('eslint').Rule.RuleContext} context */
 const create = context => {
 	const sourceCode = context.getSourceCode();
@@ -89,8 +88,8 @@ const create = context => {
 							argumentNodes[0].value + argumentNodes[1].value,
 						];
 					} else if (
-						isLikelyNumeric(argumentNodes[0])
-						&& isLikelyNumeric(argumentNodes[1])
+						isNumber(argumentNodes[0], context.getScope())
+						&& isNumber(argumentNodes[1], context.getScope())
 					) {
 						sliceArguments = [firstArgument, firstArgument + ' + ' + secondArgument];
 					}

test/prefer-string-slice.mjs

@@ -92,6 +92,11 @@ test({
 			output: '"foo".slice(1, 3)',
 			errors: errorsSubstr,
 		},
+		{
+			code: '"foo".substr(bar.length, Math.min(baz, 100))',
+			output: '"foo".slice(bar.length, bar.length + Math.min(baz, 100))',
+			errors: errorsSubstr,
+		},
 		{
 			code: '"foo".substr(1, length)',
 			errors: errorsSubstr,
@@ -110,6 +115,10 @@ test({
 				const length = 123;
 				"foo".substr(1, length)
 			`,
+			output: outdent`
+				const length = 123;
+				"foo".slice(1, 1 + length)
+			`,
 			errors: errorsSubstr,
 		},
 		{
@@ -145,6 +154,14 @@ test({
 				const length = 123;
 				"foo".substr(1, length - 4)
 			`,
+			output: outdent`
+				const length = 123;
+				"foo".slice(1, 1 + length - 4)
+			`,
+			errors: errorsSubstr,
+		},
+		{
+			code: '"foo".substr(1, length)',
 			errors: errorsSubstr,
 		},
 		{