Fix review comments

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

@@ -23,6 +23,7 @@ import * as N from "../types";
 import LValParser from "./lval";
 import { reservedWords } from "../util/identifier";
 import type { Pos, Position } from "../util/location";
+import * as charCodes from "charcodes";
 
 export default class ExpressionParser extends LValParser {
   // Forward-declaration: defined in statement.js
@@ -718,6 +719,10 @@ export default class ExpressionParser extends LValParser {
   // or `{}`.
 
   parseExprAtom(refShorthandDefaultPos?: ?Pos): N.Expression {
+    // If a division operator appears in an expression position, the
+    // tokenizer got confused, and we force it to read a regexp instead.
+    if (this.state.type === tt.slash) this.readRegexp();
+
     const canBeArrow = this.state.potentialArrowAt === this.state.start;
     let node;
 
@@ -965,9 +970,11 @@ export default class ExpressionParser extends LValParser {
   parseFunctionExpression(): N.FunctionExpression | N.MetaProperty {
     const node = this.startNode();
 
-    // We do not do parseIdentifier here because of perf but more importantly
-    // because parseIdentifier will remove an item from the expression stack
-    // if function or class is parsed as identifier (in objects e.g.).
+    // We do not do parseIdentifier here because when parseFunctionExpression
+    // is called we already know that the current token is a "name" with the value "function"
+    // This will improve perf a tiny little bit as we do not do validation but more importantly
+    // here is that parseIdentifier will remove an item from the expression stack
+    // if "function" or "class" is parsed as identifier (in objects e.g.), which should not happen here.
     let meta = this.startNode();
     this.next();
     meta = this.createIdentifier(meta, "function");
@@ -1906,7 +1913,7 @@ export default class ExpressionParser extends LValParser {
       if (
         (name === "class" || name === "function") &&
         (this.state.lastTokEnd !== this.state.lastTokStart + 1 ||
-          this.input.charCodeAt(this.state.lastTokStart) !== 46)
+          this.input.charCodeAt(this.state.lastTokStart) !== charCodes.dot)
       ) {
         this.state.context.pop();
       }

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

@@ -6,6 +6,7 @@ import * as N from "../types";
 import type { Options } from "../options";
 import type { Pos, Position } from "../util/location";
 import type State from "../tokenizer/state";
+import { types as tc } from "../tokenizer/context";
 import * as charCodes from "charcodes";
 import { isIteratorStart } from "../util/identifier";
 
@@ -2392,7 +2393,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       refNeedsArrowPos?: ?Pos,
     ): N.Expression {
       let jsxError = null;
-      if (tt.jsxTagStart && this.match(tt.jsxTagStart)) {
+      if (
+        this.hasPlugin("jsx") &&
+        (this.match(tt.jsxTagStart) || this.isRelational("<"))
+      ) {
         const state = this.state.clone();
         try {
           return super.parseMaybeAssign(
@@ -2408,7 +2412,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             // Remove `tc.j_expr` and `tc.j_oTag` from context added
             // by parsing `jsxTagStart` to stop the JSX plugin from
             // messing with the tokens
-            this.state.context.length -= 2;
+            const cLength = this.state.context.length;
+            if (this.state.context[cLength - 1] === tc.j_oTag) {
+              this.state.context.length -= 2;
+            }
 
             jsxError = err;
           } else {

packages/babel-parser/src/plugins/jsx/index.js

@@ -506,6 +506,15 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         return this.parseLiteral(this.state.value, "JSXText");
       } else if (this.match(tt.jsxTagStart)) {
         return this.jsxParseElement();
+      } else if (
+        this.isRelational("<") &&
+        this.state.input.charCodeAt(this.state.pos) !==
+          charCodes.exclamationMark
+      ) {
+        // In case we encounter an lt token here it will always be the start of
+        // jsx as the lt sign is not allowed in places that expect an expression
+        this.finishToken(tt.jsxTagStart);
+        return this.jsxParseElement();
       } else {
         return super.parseExprAtom(refShortHandDefaultPos);
       }

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

@@ -40,20 +40,6 @@ export const types: {
   template: new TokContext("`", true, true, p => p.readTmplToken()),
   functionExpression: new TokContext("function", true),
   functionStatement: new TokContext("function", false),
-  functionExpressionGenerator: new TokContext(
-    "function",
-    true,
-    false,
-    null,
-    true,
-  ),
-  functionStatementGenerator: new TokContext(
-    "function",
-    false,
-    false,
-    null,
-    true,
-  ),
 };
 
 // Token-specific context update code
@@ -72,39 +58,18 @@ tt.parenR.updateContext = tt.braceR.updateContext = function() {
   this.state.exprAllowed = !out.isExpr;
 };
 
-tt.star.updateContext = function(prevType) {
-  if (prevType === tt._function) {
-    const index = this.state.context.length - 1;
-    if (this.state.context[index] === types.functionExpression) {
-      this.state.context[index] = types.functionExpressionGenerator;
-    } else {
-      this.state.context[index] = types.functionStatementGenerator;
-    }
-  }
-  this.state.exprAllowed = true;
-};
-
 tt.name.updateContext = function(prevType) {
   let allowed = false;
   if (prevType !== tt.dot) {
     if (
       (this.state.value === "of" && !this.state.exprAllowed) ||
-      (this.state.value === "yield" && this.inGeneratorContext())
+      (this.state.value === "yield" && this.state.inGenerator)
     ) {
       allowed = true;
     }
   }
   this.state.exprAllowed = allowed;
 
-  if (prevType === tt._let || prevType === tt._const || prevType === tt._var) {
-    if (
-      lineBreak.test(
-        this.input.slice(this.state.end, this.lookahead(true).start),
-      )
-    ) {
-      this.state.exprAllowed = true;
-    }
-  }
   if (this.state.isIterator) {
     this.state.isIterator = false;
   }

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

@@ -1378,14 +1378,6 @@ export default class Tokenizer extends LocationParser {
     return !this.state.exprAllowed;
   }
 
-  inGeneratorContext() {
-    for (let i = this.state.context.length - 1; i >= 1; i--) {
-      const context = this.state.context[i];
-      if (context.token === "function") return context.generator;
-    }
-    return false;
-  }
-
   updateContext(prevType: TokenType): void {
     const type = this.state.type;
     let update;