'flattenedToList' isn't defined for the class 'Iterable<List<Folder>>'

[RazorSai]

when i try to run the command "dart run build_runner build --delete-conflicting-outputs", i'm getting the following error :-

`
Building package executable... (3.2s)
Failed to build build_runner:build_runner:
../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/analysis/driver.dart:706:39: Error: The getter 'flattenedToList' isn't defined for the class 'Iterable<List>'.

• 'Iterable' is from 'dart:core'.
• 'List' is from 'dart:core'.
• 'Folder' is from 'package:analyzer/file_system/file_system.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/file_system/file_system.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToList'.
  var folders = packageMap.values.flattenedToList;
  ^^^^^^^^^^^^^^^
  ../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/fasta/ast_builder.dart:3136:31: Error: The getter 'flattenedToList' isn't defined for the class 'List<List>'.
• 'List' is from 'dart:core'.
• 'SwitchMemberImpl' is from 'package:analyzer/src/dart/ast/ast.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/ast/ast.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToList'.
  var members = membersList.flattenedToList;
  ^^^^^^^^^^^^^^^
  ../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/element/generic_inferrer.dart:567:14: Error: The getter 'flattenedToList' isn't defined for the class 'Iterable<List<MergedTypeConstraint<DartType, TypeParameterElementImpl2, PromotableElementImpl2, InterfaceTypeImpl, InterfaceElementImpl2>>>'.
• 'Iterable' is from 'dart:core'.
• 'List' is from 'dart:core'.
• 'MergedTypeConstraint' is from 'package:_fe_analyzer_shared/src/type_inference/type_constraint.dart' ('../../../.pub-cache/hosted/pub.dev/_fe_analyzer_shared-79.0.0/lib/src/type_inference/type_constraint.dart').
• 'DartType' is from 'package:analyzer/dart/element/type.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/dart/element/type.dart').
• 'TypeParameterElementImpl2' is from 'package:analyzer/src/dart/element/element.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/element/element.dart').
• 'PromotableElementImpl2' is from 'package:analyzer/src/dart/element/element.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/element/element.dart').
• 'InterfaceTypeImpl' is from 'package:analyzer/src/dart/element/type.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/element/type.dart').
• 'InterfaceElementImpl2' is from 'package:analyzer/src/dart/element/element.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/element/element.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToList'.
  .flattenedToList;
  ^^^^^^^^^^^^^^^
  ../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/analysis/library_analyzer.dart:619:8: Error: The getter 'flattenedToSet' isn't defined for the class 'Iterable<Iterable>'.
• 'Iterable' is from 'dart:core'.
• 'ErrorCode' is from 'package:_fe_analyzer_shared/src/base/errors.dart' ('../../../.pub-cache/hosted/pub.dev/_fe_analyzer_shared-79.0.0/lib/src/base/errors.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToSet'.
  }).flattenedToSet;
  ^^^^^^^^^^^^^^
  ../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/analysis/library_graph.dart:200:10: Error: The getter 'flattenedToList' isn't defined for the class 'Iterable<List<LibraryFileKind?>>'.
• 'Iterable' is from 'dart:core'.
• 'List' is from 'dart:core'.
• 'LibraryFileKind' is from 'package:analyzer/src/dart/analysis/file_state.dart' ('../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/dart/analysis/file_state.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToList'.
  .flattenedToList
  ^^^^^^^^^^^^^^^
  ../../../.pub-cache/hosted/pub.dev/analyzer-7.2.0/lib/src/summary2/library_builder.dart:509:25: Error: The getter 'flattenedToList' isn't defined for the class 'List<List>'.
• 'List' is from 'dart:core'.
• 'MacroExecutionResult' is from 'package:_macros/src/executor.dart' ('../../flutter/flutter/bin/cache/dart-sdk/pkg/_macros/lib/src/executor.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'flattenedToList'.
  _macroResults.flattenedToList,
  ^^^^^^^^^^^^^^^
  `

[dart-github-bot]

Summary: build_runner fails due to undefined flattenedToList getter on several Iterable and List types within the analyzer package. This suggests a missing helper function or a typo in the analyzer code.

[scheglov]

You need new enough version of package:collection.
It looks that this method was added in 1.19.
And the analyzer requires

dependencies:
<cut>
  collection: ^1.19.0
<cut>