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

---------

Co-authored-by: Anton Medvedev <[email protected]>

parser/parser.go

@@ -12,7 +12,6 @@ import (
 	"github.com/expr-lang/expr/builtin"
 	"github.com/expr-lang/expr/conf"
 	"github.com/expr-lang/expr/file"
-	"github.com/expr-lang/expr/parser/lexer"
 	. "github.com/expr-lang/expr/parser/lexer"
 	"github.com/expr-lang/expr/parser/operator"
 	"github.com/expr-lang/expr/parser/utils"
@@ -49,7 +48,7 @@ var predicates = map[string]struct {
 
 // Parser is a reusable parser. The zero value is ready for use.
 type Parser struct {
-	lexer            *lexer.Lexer
+	lexer            *Lexer
 	current, stashed Token
 	hasStash         bool
 	err              *file.Error
@@ -60,7 +59,7 @@ type Parser struct {
 
 func (p *Parser) Parse(input string, config *conf.Config) (*Tree, error) {
 	if p.lexer == nil {
-		p.lexer = lexer.New()
+		p.lexer = New()
 	}
 	p.config = config
 	source := file.NewSource(input)