Analyzer should warn about uncommented use of commented type parameters

[nex3]

The following code:

foo/*<T>*/() => <T>[];

is clearly invalid; it will fail in any implementation that's not aware of the commented generic syntax, including the Dart VM. The analyzer should warn about it even in strong mode to help users avoid the failures like this.

[jmesserly]

Related to these closed bugs: #24985 (comment), #25637 (comment)

Unfortunately we don't have the capability in the architecture to catch things like this. For better or worse a decision was made early on to invest minimally in the generic method comments, to keep it easy to ditch comments when generic method syntax is implemented in the VM. I think that reasoning still holds.

(By design, the scanner is the only one that knows much about the comments -- even the parser only knows a little bit, only enough to find the comments and insert them in the token stream. The benefit is nothing after that knows about comments, so we can easily transition to the real syntax, because from most of the Analyzer's perspective, there is no comments, only the real syntax. Unfortunately, it means the comments aren't first class, and we can't do semantic analysis on them, for example, to issue errors about incorrect usage of the comment form.)

[jmesserly]

@vsmenon or @floitschG might have an update on the status of real generic method syntax?

[eernstg]

I'm working on generic method syntax for dart2js; currently we can parse most of it, but we also need to integrate the type variables with the static analysis (it might work to consider them to denote dynamic, but we haven't explored that yet). So it's coming.

[bwilkerson]

Given that support for the comment syntax is being removed, I'm going to close this issue.