implement generic functions/methods in other AST nodes besides MethodInvocation

[jmesserly]

Right now generic function calls are only supported for the MethodInvocation AST node, which applies to method calls like o.m<t>(...) and function calls like f<t>(...)

We need to support these:

• tear offs, e.g. o.m
• instantiated tear offs, e.g. o.m<t>
• instantiation of the function type, e.g. var y = f<int>;
• function expression invocation, e.g. (f)(1, 2) or (f)<int>(1, 2)
• generic function expression, e.g. <T>(T x) => x

[jmesserly]

btw feel free to edit the first message, not sure if I've captured all of the missing features

[leafpetersen]

Tear offs seem to be working. I think the partial instantiation is lower priority, particularly given that I think the work involved will be larger. I'll work on getting function expression invocation working.

[jmesserly]

@leafpetersen if you don't mind I'll take this, I think it will be pretty easy to fix to FunctionExpressionInvocation after the cleanup in https://codereview.chromium.org/1568643002/

[jmesserly]

This might belong in a different bug, but I just noticed we don't handle this case correctly:

int lambdaCall = (/*<T>*/(/*=T*/ e) => e)/*<int>*/(3);

[leafpetersen]

Sure, all yours.

[jmesserly]

https://codereview.chromium.org/1561233003/ :)

[jmesserly]

Hmmm, actually it looks like we don't support that lambda form?
https://github.com/leafpetersen/dep-generic-methods/blob/master/proposal.md#functions

In which case it's a bug in the error handling, as we should disallow type parameters there.