title: Class 'GeoJSON' incorrectly extends base class 'FeatureGroup'
body: <p>In a project of mine I get this error message:</p>
  
  <pre><code>test/node_modules/@types/leaflet/index.d.ts(856,11): error TS2415: Class 'GeoJSON' incorrectly extends base class 'FeatureGroup'.
    Types of property 'setStyle' are incompatible.
      Type '(style: StyleFunction) =&gt; this' is not assignable to type '(style: PathOptions) =&gt; this'.
        Types of parameters 'style' and 'style' are incompatible.
          Type 'PathOptions' is not assignable to type 'StyleFunction'.
            Type 'PathOptions' provides no match for the signature '(feature?: Feature&lt;GeometryObject&gt;): PathOptions'.
  </code></pre>
  
  <p>Here are the input files:</p>
  
  <p>test.ts</p>
  
  <pre><code>import { LatLngExpression } from 'leaflet'
  </code></pre>
  
  <p>package.json</p>
  
  <pre><code>{
    "name": "test",
    "version": "0.0.1",
    "description": "",
    "author": "",
    "license": "ISC",
    "devDependencies": {
      "@types/leaflet": "^1.0.68",
      "gulp": "^3.9.1",
      "gulp-typescript": "^3.2.2",
      "typescript": "^2.4.2"
    }
  }
  </code></pre>
  
  <p>tsconfig.json</p>
  
  <pre><code>{
    "compileOnSave": true,
    "compilerOptions": {
      "noEmitOnError": true,
      "target": "es5",
      "module": "amd",
      "moduleResolution": "node"
    },
    "include": [
      "test.ts"
    ]
  }
  </code></pre>
  
  <p>gulpfile.js</p>
  
  <pre><code>const gulp = require('gulp');
  const ts = require("gulp-typescript");
  
  const tsProject = ts.createProject("tsconfig.json");
  
  gulp.task('default', () =&gt; {
      const tsResult = tsProject.src().pipe(tsProject());
      return tsResult.js.pipe(gulp.dest(''));
  });
  </code></pre>
  
  <p>The error appears if I execute "yarn &amp;&amp; gulp" - but not, if I use "npm install" instead of yarn, and not if I use "tsc -p ." instead of the gulp file.
  Furthermore, as long as I had Typescript 2.4.1 there was no error at all - it appeared after I updated to Typescript 2.4.2.</p>
  
  <p>I would like to report this as a bug - but I don't know what part is responsible: yarn, typescript, gulp-typescript, @types/leaflet?</p>
  
  <p>How could I get hold of this?</p>
  
  <p>Obviously I extracted this test case from a larger project where I would like to use "yarn &amp;&amp; gulp", which leads to the error. So I would like to have a fix - not any of the "workarounds" above.</p>