Improve Performance of the Type System (#824)

* export the checker and ensure no methods or fields are exported

* make Checker reusable

* add PatchAndCheck method to Checker, and reuse it in visitors

* avoid unnecessary map and consolidate structs

* make all Nature methods use pointer-receiver

* added cache for type and nature information

* optimize type and nature checks

* more aggressively cache some partial results and add cheap checks

* cache reused values

* reduce copying in Nature by breaking down optional fields

* enforce use of cache

* improve ergonomics of FromType and NatureOf

* improve struct method fetching

* make cache private to Nature

* first iteration improving struct reflect caching

* cleaned up struct fields data

* improve caching of functions data

* simplify checker code

* simplify and remove dead code

* add checker benchmarks

* address PR comments and minor improvements

* rename from SetCache to Bind

* make the benchmarks more fair

* fix benchmark option not being applied

* move Cache to be argument instead of field

* merge FuncData into Optional

* rename Optional to TypeData

* simplify struct logic

* cache builtin numeric types

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Co-authored-by: Anton Medvedev <anton@medv.io>

Author: diegommm

ast/node.go

@@ -66,7 +66,7 @@ func (n *base) Type() reflect.Type {
 
 // SetType sets the type of the node.
 func (n *base) SetType(t reflect.Type) {
-	n.nature.Type = t
+	n.nature = nature.FromType(t)
 }
 
 // NilNode represents nil.