Inferring types related to System.Text.RegularExpressions

[webnov8]

Currently when you try enumerating over a MatchCollection? the type returned is Object?

For e.g. let's say we wanted to find all occurrences of @param in a file...

str = '' # some string
for match in Regex.Match(str, r'^\s*@param\s+(.*)$')
  # we expect a string to be located in the group identified by (.*)
  groups = match.groups # this will not work because match is of type Object?

Specifying the type works as expected as in...

for match as Match in Regex.Match(...)

[Chuck]

The problem is that MatchCollection? implements IEnumerable, but not IEnumerable<of T>. The idea for fixing this is to look at the indexer for the type and use its return value. This problem comes up for other .NET library classes that were built prior to .NET 2.0 generics.

It would be interesting to know if C# 3.0's var can useful inference on this.

[torial]

FWIW, when I tried it in C# 3, it wouldn't compile and gave me:

'object' does not contain a definition for 'Groups' and no extension method 'Groups' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?)

[hopscc]

Example above should be referring to Regex.matches. ( returns MatchCollection)
Similar issue with GroupCollection.

Patch to support this includes test case and release note.
Fix is to do additional check if IEnumeration result type is Object.
Look at indexer ([]) return type and provide that if its not Object.

[Chuck]

Applied in changeset:2358. In changeset:2359 I switch up the code to use Box.isSystemObjectClass to avoid picking up a user class named 'Object'.