Proposed resolution:

lambda-expression:
      lambda-introducer lambda-declaratoropt compound-statement
...

lambda-declarator:
      ( parameter-declaration-clause ) mutableopt
            exception-specificationopt attribute-specifier-seqopt trailing-return-typeopt
      mutableopt exception-specificationopt attribute-specifier-seqopt trailing-return-typeopt

If a lambda-expression does not include a lambda-declarator, it is as if the lambda-declarator were ().

This function call operator or operator template is declared const (9.3.1) if and only if the lambda-expression's parameter-declaration-clause is not followed by lambda-declarator does not contain the keyword mutable.