Problems reported:

parser/error_recovery/issue_45251_set:3:31: A set literal can't be prefixed by 'Set'.
  final Set<Undefined> foo1 = Set<List<int>>{};
                              ^^^

parser/error_recovery/issue_45251_set:9:31: A set literal can't be prefixed by 'Set'.
  final Set<Undefined> foo3 = Set{};
                              ^^^

parser/error_recovery/issue_45251_set:18:31: A set literal can't be prefixed by 'Set'.
  final Set<Undefined> foo6 = Set<List<int>>{null};
                              ^^^

parser/error_recovery/issue_45251_set:21:31: A set literal can't be prefixed by 'Set'.
  final Set<Undefined> foo7 = Set{null};
                              ^^^

beginCompilationUnit(class)
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          beginFields({)
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              handleIdentifier(Undefined, typeReference)
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            handleType(Set, null)
            handleIdentifier(foo1, fieldDeclaration)
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              handleRecoverableError(Message[LiteralWithClass, A set literal can't be prefixed by 'Set'., Try removing 'Set', {string: set, lexeme: Set}], Set, Set)
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                handleType(List, null)
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            endFieldInitializer(=, ;)
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              handleType(Undefined, null)
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            handleType(Set, null)
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            beginFieldInitializer(=)
              beginTypeArguments(<)
                handleIdentifier(List, typeReference)
                beginTypeArguments(<)
                  handleIdentifier(int, typeReference)
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                  handleType(int, null)
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                handleType(List, null)
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            handleType(Set, null)
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              handleRecoverableError(Message[LiteralWithClass, A set literal can't be prefixed by 'Set'., Try removing 'Set', {string: set, lexeme: Set}], Set, Set)
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              handleType(Undefined, null)
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            handleType(Set, null)
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              handleRecoverableError(Message[LiteralWithClass, A set literal can't be prefixed by 'Set'., Try removing 'Set', {string: set, lexeme: Set}], Set, Set)
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                handleIdentifier(List, typeReference)
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                  handleIdentifier(int, typeReference)
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                endTypeArguments(1, <, >)
                handleType(List, null)
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              handleRecoverableError(Message[LiteralWithClass, A set literal can't be prefixed by 'Set'., Try removing 'Set', {string: set, lexeme: Set}], Set, Set)
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endCompilationUnit(1, )