Remove the lamdba allocation during TypeRegistry`1.TryGetValue (which…

[ndrwrbgs]

… is called indirectly by Template.Render())

.Where(i => i.IsAssignableFrom(key)) is using key which is captured from the surrounding closure. Therefore, the runtime allocates a new object to capture the Func<Type, bool> paired with it's required key input (rather than if there were, say, a WhereWithState<TSource, TState, TResult>(TSource, TState) method).

Since this is called by Template.Render() it adds unnecessary overhead we can remove without changes to the runtime by expanding the LINQ statement into a foreach loop.

[ndrwrbgs]

The travis-ci build seems to have been failed for unrelated reasons, the actual test run passed

Total tests: 610. Passed: 606. Failed: 0. Skipped: 4.
Test Run Successful.
Test execution time: 3.2077 Seconds
The command "dotnet test Antlr4.Test.StringTemplate -f netcoreapp2.0" exited with 0.

[sharwell]

Can we keep the current form, and avoid capturing the parameter on the fast path by moving the slow path code to TryGetValueSlow? If you aren't familiar with this pattern let me know and I can write it out when I'm at a computer tomorrow.

[ndrwrbgs]

I don't think it does the allocariok unless this code is hit, unless I misunderstand something grave. And if this code is being hit then it'd be hit in another method if moved anyway, right?

I know it shouldn't be hit frequently given there's a cache but why not avoid the allocation even on cache miss? :)