Lint for missing type info in formal parameter

[pq]

Discovered in the wild a number of cases like this:

typedef A(B);
typedef B(dynamic);

Both of them are essentially equivalent to dynamic->dynamic which is most likely not what the user has in mind. Instead, they likely mean:

typedef A(B _);
typedef B(dynamic _);

As Paul Berry points out it's a nasty user trap in the language, especially for people coming from a C/C++ background where using a single identifier as a formal parameter denotes the type of the formal parameter. A proposed lint:

whenever a single identifier is used to name a formal parameter, check the enclosing scope to see if
the name shadows a type. If it does, give a hint because the user probably meant the identifier to
denote the type of the formal parameter. We could even add a quick fix which adds "_" as the
parameter name.

[ochafik]

An easy way to tackle this would be to check that argument names start with lowercase. And a similar check for method names would help spot another sneaky case:

class MyClassNameBeforeRefactoring {
  // oops, forgot to rename the constructor...
  MyClassNameAfterRefactoring() {
    // something important that will never happen
  }
}

[zoechi]

@ochafik for your case a rule for functions and methods like http://dart-lang.github.io/linter/lints/non_constant_identifier_names.html would be nice to catch this.

[dotdoom]

Looks like this will become irrelevant when the old typedef syntax becomes obsolete?

[srawlins]

Yeah I think we've likely dodged this by recommending the new typedef format.