Turn on no-fallthrough rule (#11093)

* chore: turn on no-fallthrough

* chore: fix no-fallthrough errors

babel.config.js

@@ -36,6 +36,7 @@ module.exports = function(api) {
     case "standalone":
       includeRegeneratorRuntime = true;
       unambiguousSources.push("packages/babel-runtime/regenerator");
+    // fall through
     case "rollup":
       convertESM = false;
       ignoreLib = false;

eslint/babel-eslint-config-internal/index.js

@@ -30,7 +30,6 @@ module.exports = {
     "no-console": "off",
     "no-constant-condition": "off",
     "no-empty": "off",
-    "no-fallthrough": "off",
     "no-inner-declarations": "off",
     "no-labels": "off",
     "no-loop-func": "off",

packages/babel-core/src/config/files/module-types.js

@@ -21,6 +21,7 @@ export default function* loadCjsOrMjsDefault(
       } catch (e) {
         if (e.code !== "ERR_REQUIRE_ESM") throw e;
       }
+    // fall through
     case "mjs":
       if (yield* isAsync()) {
         return yield* waitFor(loadMjsDefault(filepath));

packages/babel-parser/src/parser/expression.js

@@ -1058,7 +1058,7 @@ export default class ExpressionParser extends LValParser {
 
       case tt.at:
         this.parseDecorators();
-
+      // fall through
       case tt._class:
         node = this.startNode();
         this.takeDecorators(node);
@@ -1111,7 +1111,7 @@ export default class ExpressionParser extends LValParser {
           return this.finishNode(node, "PipelinePrimaryTopicReference");
         }
       }
-
+      // fall through
       default:
         throw this.unexpected();
     }

packages/babel-parser/src/plugins/flow.js

@@ -1441,7 +1441,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             );
           }
 
-          this.unexpected();
+          throw this.unexpected();
         case tt.num:
           return this.parseLiteral(
             this.state.value,

packages/babel-parser/src/tokenizer/index.js

@@ -332,7 +332,7 @@ export default class Tokenizer extends LocationParser {
           ) {
             ++this.state.pos;
           }
-
+        // fall through
         case charCodes.lineFeed:
         case charCodes.lineSeparator:
         case charCodes.paragraphSeparator:
@@ -736,7 +736,7 @@ export default class Tokenizer extends LocationParser {
         }
       }
       // Anything else beginning with a digit is an integer, octal
-      // number, or float.
+      // number, or float. (fall through)
       case charCodes.digit1:
       case charCodes.digit2:
       case charCodes.digit3:
@@ -1221,6 +1221,7 @@ export default class Tokenizer extends LocationParser {
             if (this.input.charCodeAt(this.state.pos) === charCodes.lineFeed) {
               ++this.state.pos;
             }
+          // fall through
           case charCodes.lineFeed:
             out += "\n";
             break;
@@ -1268,9 +1269,11 @@ export default class Tokenizer extends LocationParser {
         if (this.input.charCodeAt(this.state.pos) === charCodes.lineFeed) {
           ++this.state.pos;
         }
+      // fall through
       case charCodes.lineFeed:
         this.state.lineStart = this.state.pos;
         ++this.state.curLine;
+      // fall through
       case charCodes.lineSeparator:
       case charCodes.paragraphSeparator:
         return "";
@@ -1279,6 +1282,7 @@ export default class Tokenizer extends LocationParser {
         if (inTemplate) {
           return null;
         }
+      // fall through
       default:
         if (ch >= charCodes.digit0 && ch <= charCodes.digit7) {
           const codePos = this.state.pos - 1;

packages/babel-types/src/validators/isReferenced.js

@@ -54,16 +54,18 @@ export default function isReferenced(
       if (parent.params.includes(node)) {
         return false;
       }
-    // Fall-through to next case clause to check whether the node is the method's name.
+    // fall through
 
     // yes: { [NODE]: "" }
     // no: { NODE: "" }
     // depends: { NODE }
     // depends: { key: NODE }
+    // fall through
     case "ObjectProperty":
     // no: class { NODE = value; }
     // yes: class { [NODE] = value; }
     // yes: class { key = NODE; }
+    // fall through
     case "ClassProperty":
     case "ClassPrivateProperty":
       if (parent.key === node) {