"let-" is only supported on ng-template elements.

Bug description:

After Updating to the latest Angular Packages. I get a build error:

Compiling ng-bootstrap : module as esm5
Error: Error on worker #7: Error: Template parse errors:
"let-" is only supported on ng-template elements. ("</b></small>\n      </th>\n    </tr>\n  </thead>\n  <tbody>\n    <template ngFor [ngForOf]=\"rows\" [ERROR ->]let-rowz=\"$implicit\" let-index=\"index\">\n      <tr *ngIf=\"!(datePicker.onlyCurrentMonth && rowz["): C:/Projekte/ /  /node_modules/ng-bootstrap/datepicker/daypicker.component.js@110:1658
"let-" is only supported on ng-template elements. ("h>\n    </tr>\n  </thead>\n  <tbody>\n    <template ngFor [ngForOf]=\"rows\" let-rowz=\"$implicit\" [ERROR ->]let-index=\"index\">\n      <tr *ngIf=\"!(datePicker.onlyCurrentMonth && rowz[0].secondary && rowz[6]"): C:/Projekte/ /  /node_modules/ng-bootstrap/datepicker/daypicker.component.js@110:1681
    at syntaxError (C:\Projekte\ \  \node_modules\@angular\compiler\bundles\compiler.umd.js:2724:21)
    at htmlAstToRender3Ast (C:\Projekte\ \  \node_modules\@angular\compiler\bundles\compiler.umd.js:15846:19)
    at Object.parseTemplate (C:\Projekte\ \  \node_modules\@angular\compiler\bundles\compiler.umd.js:18707:18)
    at ComponentDecoratorHandler._parseTemplate (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\annotations\src\component.js:694:33)
    at ComponentDecoratorHandler._extractInlineTemplate (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\annotations\src\component.js:671:33)
    at ComponentDecoratorHandler.analyze (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\annotations\src\component.js:204:37)
    at NgccTraitCompiler.TraitCompiler.analyzeTrait (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\transform\src\compilation.js:341:40)
    at analyze (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\transform\src\compilation.js:293:58)
    at _loop_1 (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\transform\src\compilation.js:315:21)
    at NgccTraitCompiler.TraitCompiler.analyzeClass (C:\Projekte\ \  \node_modules\@angular\compiler-cli\src\ngtsc\transform\src\compilation.js:321:35)
    at ClusterMaster.onWorkerMessage (C:\Projekte\ \  \node_modules\@angular\compiler-cli\ngcc\src\execution\cluster\master.js:166:27)
    at C:\Projekte\ \  \node_modules\@angular\compiler-cli\ngcc\src\execution\cluster\master.js:50:95
    at ClusterMaster.<anonymous> (C:\Projekte\ \  \node_modules\@angular\compiler-cli\ngcc\src\execution\cluster\master.js:246:57)
    at step (C:\Projekte\ \  \node_modules\tslib\tslib.js:139:27)
    at Object.next (C:\Projekte\ \  \node_modules\tslib\tslib.js:120:57)
    at C:\Projekte\ \  \node_modules\tslib\tslib.js:113:75
    at new Promise (<anonymous>)
    at Object.__awaiter (C:\Projekte\ \  \node_modules\tslib\tslib.js:109:16)
    at EventEmitter.<anonymous> (C:\Projekte\ \  \node_modules\@angular\compiler-cli\ngcc\src\execution\cluster\master.js:240:32)
    at EventEmitter.emit (events.js:321:20)

Versions of Angular, ng-bootstrap and Bootstrap:

Angular: “@angular/core”: “~9.1.0”, ng-bootstrap: “@ng-bootstrap/ng-bootstrap”: “^6.0.2”, Bootstrap: “bootstrap”: “^4.4.1”,

[guillermolam]

Solved by removing an old dependency from package.json “ng-bootstrap”: “^1.6.3”,

...
"@ng-bootstrap/ng-bootstrap": "^6.1.0",
"bootstrap": "^4.4.1",
## "ng-bootstrap": "^1.6.3", ## Remove this

[rissom]

Solved it! Unfortunately I really have no idea what I did. But I think cleaning up angular.json and package.json helped. Also checking package versions with

npm outdated

and updating packages to their current version with

npm install <packagename>@latest.

Thanks for the help!