error TS1086: An accessor cannot be declared in an

Question

I'm learning Angular Material and I'm getting this error when importing { MatButtonModule } from "@angular/material/button".

From what I read in other answers, it looks like package compatibility issues but I couldn't fix it.

Here's the full error

ERROR in node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(29,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(30,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(128,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(129,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(134,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/focus-trap/focus-trap.d.ts(135,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/key-manager/list-key-manager.d.ts(96,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/key-manager/list-key-manager.d.ts(98,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/live-announcer/live-announcer.d.ts(69,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/a11y/live-announcer/live-announcer.d.ts(70,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/observers/observe-content.d.ts(62,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/observers/observe-content.d.ts(63,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/observers/observe-content.d.ts(66,9): error TS1086: An accessor cannot be declared in an ambient context.
    node_modules/@angular/cdk/observers/observe-content.d.ts(67,9): error TS1086: An accessor cannot be declared in an ambient context.

Here's my package.json

"name": "football",
  "version": "0.0.0",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "~8.2.14",
    "@angular/cdk": "^9.0.0",
    "@angular/common": "~8.2.14",
    "@angular/compiler": "~8.2.14",
    "@angular/core": "~8.2.14",
    "@angular/forms": "~8.2.14",
    "@angular/material": "8.2.3",
    "@angular/platform-browser": "~8.2.14",
    "@angular/platform-browser-dynamic": "~8.2.14",
    "@angular/router": "~8.2.14",
    "hammerjs": "^2.0.8",
    "rxjs": "~6.4.0",
    "tslib": "^1.10.0",
    "zone.js": "~0.9.1"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.803.21",
    "@angular/cli": "~8.3.21",
    "@angular/compiler-cli": "~8.2.14",
    "@angular/language-service": "~8.2.14",
    "@types/node": "~8.9.4",
    "@types/jasmine": "~3.3.8",
    "@types/jasminewd2": "~2.0.3",
    "codelyzer": "^5.0.0",
    "jasmine-core": "~3.4.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~4.1.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "~2.0.1",
    "karma-jasmine": "~2.0.1",
    "karma-jasmine-html-reporter": "^1.4.0",
    "protractor": "~5.4.0",
    "ts-node": "~7.0.0",
    "tslint": "~5.15.0",
    "typescript": "~3.5.3"
  }
}

Answer 1

First please check in module.ts file that in @NgModule all properties are only one time. If any of are more than one time then also this error come. Because I had also occur this error but in module.ts file entryComponents property were two time that's why I was getting this error. I resolved this error by removing one time entryComponents from @NgModule. So, I recommend that first you check it properly.

Answer 2

According to your package.json, you're using Angular 8.3, but you've imported angular/cdk v9. You can downgrade your angular/cdk version or you can upgrade your Angular version to v9 by running:

ng update @angular/core @angular/cli

That will update your local angular version to 9. Then, just to sync material, run: ng update @angular/material