feat: make no-misleading-character-class report more granular errors

lib/rules/utils/char-source.js

@@ -32,6 +32,12 @@ class SourceReader {
         this.source = source;
         this.pos = 0;
     }
+
+    read(offset = 0, length = 1) {
+        const start = offset + this.pos;
+
+        return this.source.slice(start, start + length);
+    }
 }
 
 const SIMPLE_ESCAPE_SEQUENCES =
@@ -44,11 +50,10 @@ const SIMPLE_ESCAPE_SEQUENCES =
  * @returns {string} A code unit.
  */
 function readHexSequence(reader, length) {
-    const { source, pos } = reader;
-    const str = source.slice(pos, pos + length);
+    const str = reader.read(0, length);
     const charCode = parseInt(str, 16);
 
-    reader.pos = pos + length;
+    reader.pos += length;
     return String.fromCharCode(charCode);
 }
 
@@ -58,11 +63,10 @@ function readHexSequence(reader, length) {
  * @returns {string} A code unit.
  */
 function readUnicodeSequence(reader) {
-    const { source, pos } = reader;
     const regExp = /\{(?<hexDigits>[\dA-Fa-f]+)\}/uy;
 
-    regExp.lastIndex = pos;
-    const match = regExp.exec(source);
+    regExp.lastIndex = reader.pos;
+    const match = regExp.exec(reader.source);
 
     if (match) {
         const codePoint = parseInt(match.groups.hexDigits, 16);
@@ -80,25 +84,23 @@ function readUnicodeSequence(reader) {
  * @returns {string} A code unit.
  */
 function readOctalSequence(reader, maxLength) {
-    const posAfterBackslash = reader.pos - 1;
-    const [octalStr] = reader.source.slice(posAfterBackslash, posAfterBackslash + maxLength).match(/^[0-7]+/u);
+    const [octalStr] = reader.read(-1, maxLength).match(/^[0-7]+/u);
 
-    reader.pos = posAfterBackslash + octalStr.length;
+    reader.pos += octalStr.length - 1;
     const octal = parseInt(octalStr, 8);
 
     return String.fromCharCode(octal);
 }
 
 /**
  * Reads an escape sequence or line continuation.
- * @param {SourceReader} reader The reader should be positioned after the backslash.
+ * @param {SourceReader} reader The reader should be positioned on the backslash.
  * @returns {string} A string of zero, one or two code units.
  */
 function readEscapeSequenceOrLineContinuation(reader) {
-    const { source, pos } = reader;
-    const char = source[pos];
+    const char = reader.read(1);
 
-    reader.pos = pos + 1;
+    reader.pos += 2;
     const unitChar = SIMPLE_ESCAPE_SEQUENCES[char];
 
     if (unitChar) {
@@ -110,8 +112,8 @@ function readEscapeSequenceOrLineContinuation(reader) {
         case "u":
             return readUnicodeSequence(reader);
         case "\r":
-            if (source[pos + 1] === "\n") {
-                reader.pos = pos + 2;
+            if (reader.read() === "\n") {
+                reader.pos += 1;
             }
 
             // fallthrough
@@ -140,7 +142,7 @@ function readEscapeSequenceOrLineContinuation(reader) {
  * @returns {Generator<CodeUnit>} Zero, one or two `CodeUnit` elements.
  */
 function *mapEscapeSequenceOrLineContinuation(reader) {
-    const start = reader.pos++;
+    const start = reader.pos;
     const str = readEscapeSequenceOrLineContinuation(reader);
     const end = reader.pos;
     const source = reader.source.slice(start, end);
@@ -165,23 +167,22 @@ function *mapEscapeSequenceOrLineContinuation(reader) {
  */
 function parseStringLiteral(source) {
     const reader = new SourceReader(source);
-    const quote = source[0];
+    const quote = reader.read();
 
     reader.pos = 1;
     const codeUnits = [];
 
     for (;;) {
-        const { pos } = reader;
-        const char = source[pos];
+        const char = reader.read();
 
         if (char === quote) {
             break;
         }
         if (char === "\\") {
             codeUnits.push(...mapEscapeSequenceOrLineContinuation(reader));
         } else {
-            reader.pos = pos + 1;
-            codeUnits.push(new CodeUnit(pos, char));
+            codeUnits.push(new CodeUnit(reader.pos, char));
+            reader.pos += 1;
         }
     }
     return codeUnits;
@@ -199,25 +200,23 @@ function parseTemplateToken(source) {
     const codeUnits = [];
 
     for (;;) {
-        const { pos } = reader;
-        const char = source[pos];
+        const char = reader.read();
 
-        if (char === "`" || char === "$" && source[pos + 1] === "{") {
+        if (char === "`" || char === "$" && reader.read(1) === "{") {
             break;
         }
         if (char === "\\") {
             codeUnits.push(...mapEscapeSequenceOrLineContinuation(reader));
         } else {
             let unitSource;
 
-            if (char === "\r" && source[pos + 1] === "\n") {
+            if (char === "\r" && reader.read(1) === "\n") {
                 unitSource = "\r\n";
-                reader.pos = pos + 2;
             } else {
                 unitSource = char;
-                reader.pos = pos + 1;
             }
-            codeUnits.push(new CodeUnit(pos, unitSource));
+            codeUnits.push(new CodeUnit(reader.pos, unitSource));
+            reader.pos += unitSource.length;
         }
     }
     return codeUnits;