Flow comment parsing (#7007)

packages/babylon/src/plugins/flow.js

@@ -7,6 +7,7 @@ import { types as tt, type TokenType } from "../tokenizer/types";
 import * as N from "../types";
 import type { Pos, Position } from "../util/location";
 import type State from "../tokenizer/state";
+import * as charCodes from "charcodes";
 
 const primitiveTypes = [
   "any",
@@ -2278,4 +2279,66 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         /* isAsync */ true,
       );
     }
+
+    readToken_mult_modulo(code: number): void {
+      const next = this.input.charCodeAt(this.state.pos + 1);
+      if (
+        code === charCodes.asterisk &&
+        next === charCodes.slash &&
+        this.state.hasFlowComment
+      ) {
+        this.state.hasFlowComment = false;
+        this.state.pos += 2;
+        this.nextToken();
+        return;
+      }
+
+      super.readToken_mult_modulo(code);
+    }
+
+    skipBlockComment(): void {
+      if (
+        this.hasPlugin("flow") &&
+        this.hasPlugin("flowComments") &&
+        this.skipFlowComment()
+      ) {
+        this.hasFlowCommentCompletion();
+        this.state.pos += this.skipFlowComment();
+        this.state.hasFlowComment = true;
+        return;
+      }
+
+      let end;
+      if (this.hasPlugin("flow") && this.state.hasFlowComment) {
+        end = this.input.indexOf("*-/", (this.state.pos += 2));
+        if (end === -1) this.raise(this.state.pos - 2, "Unterminated comment");
+        this.state.pos = end + 3;
+        return;
+      }
+
+      super.skipBlockComment();
+    }
+
+    skipFlowComment(): number | boolean {
+      const ch2 = this.input.charCodeAt(this.state.pos + 2);
+      const ch3 = this.input.charCodeAt(this.state.pos + 3);
+
+      if (ch2 === charCodes.colon && ch3 === charCodes.colon) {
+        return 4; // check for /*::
+      }
+      if (this.input.slice(this.state.pos + 2, 14) === "flow-include") {
+        return 14; // check for /*flow-include
+      }
+      if (ch2 === charCodes.colon && ch3 !== charCodes.colon && 2) {
+        return 2; // check for /*:, advance only 2 steps
+      }
+      return false;
+    }
+
+    hasFlowCommentCompletion(): void {
+      const end = this.input.indexOf("*/", this.state.pos);
+      if (end === -1) {
+        this.raise(this.state.pos, "Unterminated comment");
+      }
+    }
   };