Save the types in the typechecked syntax tree

When working on development tools that use the GHC API as a backend, it is useful to have information on the types (or kinds) of the elements of the syntax tree (expressions, patterns, types).

I found that the lack of this semantic information is limiting in some cases of refactoring transformations (for example to generate the type signature or extract a subexpression to a binding with type signature), and is necessary for tools that try to fix common programmer errors. But there should be other kind of tools that this little change may help.

The type is currently saved for some expressions and most patterns but it would be useful if it would be available uniformly.

It could be implemented nicely by adding type information to the X* GhcTc type families.

I plan to implement these changes, I'm just asking the opinion of the developers about a change in this direction.

Trac metadata

Trac field	Value
Version	8.4.3
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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