The following example causes 3 error Multiple default exports import/export errors, but there is only technically 1 default export the other 2 are overloads.

export default function foo(param: string): boolean;
export default function foo(param: string, param1: number): boolean;
export default function foo(param: string, param1?: number): boolean {
  return param && param1;
}

There seems to be some code for checking overloads: https://github.com/benmosher/eslint-plugin-import/blob/master/src/rules/export.js#L37-L40 but this does not seem to catch this case. I added some debug logs in and the rough contents of namespace is:

root: {
  default: [
    {
       type: 'ExportDefaultDeclaration'
    },
    {
       type: 'ExportDefaultDeclaration'
    },
    {
       type: 'ExportDefaultDeclaration'
    }
  ]
}

I am running this in the following environment:

• eslint: 5.16.0
• eslint-plugin-import: 2.19.1
• eslint-import-resolver-typescript: 2.0.0
• typescript: 3.7.2
• @typescript-eslint/parser: 2.13.0

Related:

• no-duplicate-default-export #22 (comment)
• import/export: false positives for typescript overloads #1357