Function verifyDeclarationIsUnique

packages/core/src/render3/jit/module.ts:361–383

(type: Type<any>, suppressErrors: boolean)

  }

  function verifyDeclarationIsUnique(type: Type<any>, suppressErrors: boolean) {
    type = resolveForwardRef(type);
    const existingModule = ownerNgModule.get(type);
    if (existingModule && existingModule !== moduleType) {
      if (!suppressErrors) {
        const modules = [existingModule, moduleType].map(stringifyForError).sort();
        errors.push(
          `Type ${stringifyForError(type)} is part of the declarations of 2 modules: ${
            modules[0]
          } and ${modules[1]}! ` +
            `Please consider moving ${stringifyForError(type)} to a higher module that imports ${
              modules[0]
            } and ${modules[1]}. ` +
            `You can also create a new NgModule that exports and includes ${stringifyForError(
              type,
            )} then import that NgModule in ${modules[0]} and ${modules[1]}.`,
        );
      }
    } else {
      // Mark type as having owner.
      ownerNgModule.set(type, moduleType);
    }
  }

  function verifyComponentIsPartOfNgModule(type: Type<any>) {
    type = resolveForwardRef(type);