'Debug Failure: Unexpected Node' when using a JSDoc type with a decorator

[refi64]

TypeScript Version: Nightly, 3.8.3

Search Terms: jsdoc, "unexpected node"

Expected behavior: Compilation to show an error. (I accidentally used a JSDoc type, jumping between too many different languages at once...)

Actual behavior: TypeScript crashed, from the CLI it crashed even before any diagnostics were printed:

/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:81040
                throw e;
                ^

Error: Debug Failure. Unexpected node.
Node 297 was unexpected.
    at serializeTypeNode (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64374:37)
    at serializeTypeOfNode (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64249:28)
    at addOldTypeMetadata (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64191:92)
    at addTypeMetadata (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64185:17)
    at transformAllDecoratorsOfDeclaration (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64104:13)
    at generateClassElementDecorationExpression (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64129:40)
    at generateClassElementDecorationExpressions (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64115:34)
    at addClassElementDecorationStatements (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:64108:44)
    at visitClassDeclaration (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:63906:13)
    at visitTypeScript (/var/home/ryan/code/bkglass/proxissh/node_modules/typescript/lib/tsc.js:63795:28)
error Command failed with exit code 1.

From the playground, the error is a bit different and a diagnostic is shown first:

Uncaught (in promise) Error: Debug Failure. Unexpected node.
Node JSDocNullableType was unexpected.
    at ae (tsWorker.js:21)
    at ne (tsWorker.js:21)
    at tsWorker.js:21
    at tsWorker.js:21
    at q (tsWorker.js:21)
    at X (tsWorker.js:21)
    at tsWorker.js:21
    at J (tsWorker.js:21)
    at tsWorker.js:21
    at F (tsWorker.js:21)

Related Issues: #27999 seems similar

Code

declare function decorator(): PropertyDecorator

class X {
    @decorator()
    foo?: string?
}

Note that this requires emitDecoratorMetadata: true and experimentalDecorators: true.

Output

"use strict";
X;
{
    foo ?  : string ?
        :
    ;
}

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "useDefineForClassFields": false,
    "alwaysStrict": true,
    "allowUnreachableCode": false,
    "allowUnusedLabels": false,
    "downlevelIteration": false,
    "noEmitHelpers": false,
    "noLib": false,
    "noStrictGenericChecks": false,
    "noUnusedLocals": false,
    "noUnusedParameters": false,
    "esModuleInterop": true,
    "preserveConstEnums": false,
    "removeComments": false,
    "skipLibCheck": false,
    "checkJs": false,
    "allowJs": false,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "target": "ES2017",
    "module": "ESNext"
  }
}

Playground Link: Provided

EDIT: Please ignore the title rename, I hit Enter too soon by accident...