--- /dev/null
+package inspector
+
+// This file defines func typeOf(ast.Node) uint64.
+//
+// The initial map-based implementation was too slow;
+// see https://go-review.googlesource.com/c/tools/+/135655/1/go/ast/inspector/inspector.go#196
+
+import "go/ast"
+
+const (
+ nArrayType = iota
+ nAssignStmt
+ nBadDecl
+ nBadExpr
+ nBadStmt
+ nBasicLit
+ nBinaryExpr
+ nBlockStmt
+ nBranchStmt
+ nCallExpr
+ nCaseClause
+ nChanType
+ nCommClause
+ nComment
+ nCommentGroup
+ nCompositeLit
+ nDeclStmt
+ nDeferStmt
+ nEllipsis
+ nEmptyStmt
+ nExprStmt
+ nField
+ nFieldList
+ nFile
+ nForStmt
+ nFuncDecl
+ nFuncLit
+ nFuncType
+ nGenDecl
+ nGoStmt
+ nIdent
+ nIfStmt
+ nImportSpec
+ nIncDecStmt
+ nIndexExpr
+ nInterfaceType
+ nKeyValueExpr
+ nLabeledStmt
+ nMapType
+ nPackage
+ nParenExpr
+ nRangeStmt
+ nReturnStmt
+ nSelectStmt
+ nSelectorExpr
+ nSendStmt
+ nSliceExpr
+ nStarExpr
+ nStructType
+ nSwitchStmt
+ nTypeAssertExpr
+ nTypeSpec
+ nTypeSwitchStmt
+ nUnaryExpr
+ nValueSpec
+)
+
+// typeOf returns a distinct single-bit value that represents the type of n.
+//
+// Various implementations were benchmarked with BenchmarkNewInspector:
+// GOGC=off
+// - type switch 4.9-5.5ms 2.1ms
+// - binary search over a sorted list of types 5.5-5.9ms 2.5ms
+// - linear scan, frequency-ordered list 5.9-6.1ms 2.7ms
+// - linear scan, unordered list 6.4ms 2.7ms
+// - hash table 6.5ms 3.1ms
+// A perfect hash seemed like overkill.
+//
+// The compiler's switch statement is the clear winner
+// as it produces a binary tree in code,
+// with constant conditions and good branch prediction.
+// (Sadly it is the most verbose in source code.)
+// Binary search suffered from poor branch prediction.
+//
+func typeOf(n ast.Node) uint64 {
+ // Fast path: nearly half of all nodes are identifiers.
+ if _, ok := n.(*ast.Ident); ok {
+ return 1 << nIdent
+ }
+
+ // These cases include all nodes encountered by ast.Inspect.
+ switch n.(type) {
+ case *ast.ArrayType:
+ return 1 << nArrayType
+ case *ast.AssignStmt:
+ return 1 << nAssignStmt
+ case *ast.BadDecl:
+ return 1 << nBadDecl
+ case *ast.BadExpr:
+ return 1 << nBadExpr
+ case *ast.BadStmt:
+ return 1 << nBadStmt
+ case *ast.BasicLit:
+ return 1 << nBasicLit
+ case *ast.BinaryExpr:
+ return 1 << nBinaryExpr
+ case *ast.BlockStmt:
+ return 1 << nBlockStmt
+ case *ast.BranchStmt:
+ return 1 << nBranchStmt
+ case *ast.CallExpr:
+ return 1 << nCallExpr
+ case *ast.CaseClause:
+ return 1 << nCaseClause
+ case *ast.ChanType:
+ return 1 << nChanType
+ case *ast.CommClause:
+ return 1 << nCommClause
+ case *ast.Comment:
+ return 1 << nComment
+ case *ast.CommentGroup:
+ return 1 << nCommentGroup
+ case *ast.CompositeLit:
+ return 1 << nCompositeLit
+ case *ast.DeclStmt:
+ return 1 << nDeclStmt
+ case *ast.DeferStmt:
+ return 1 << nDeferStmt
+ case *ast.Ellipsis:
+ return 1 << nEllipsis
+ case *ast.EmptyStmt:
+ return 1 << nEmptyStmt
+ case *ast.ExprStmt:
+ return 1 << nExprStmt
+ case *ast.Field:
+ return 1 << nField
+ case *ast.FieldList:
+ return 1 << nFieldList
+ case *ast.File:
+ return 1 << nFile
+ case *ast.ForStmt:
+ return 1 << nForStmt
+ case *ast.FuncDecl:
+ return 1 << nFuncDecl
+ case *ast.FuncLit:
+ return 1 << nFuncLit
+ case *ast.FuncType:
+ return 1 << nFuncType
+ case *ast.GenDecl:
+ return 1 << nGenDecl
+ case *ast.GoStmt:
+ return 1 << nGoStmt
+ case *ast.Ident:
+ return 1 << nIdent
+ case *ast.IfStmt:
+ return 1 << nIfStmt
+ case *ast.ImportSpec:
+ return 1 << nImportSpec
+ case *ast.IncDecStmt:
+ return 1 << nIncDecStmt
+ case *ast.IndexExpr:
+ return 1 << nIndexExpr
+ case *ast.InterfaceType:
+ return 1 << nInterfaceType
+ case *ast.KeyValueExpr:
+ return 1 << nKeyValueExpr
+ case *ast.LabeledStmt:
+ return 1 << nLabeledStmt
+ case *ast.MapType:
+ return 1 << nMapType
+ case *ast.Package:
+ return 1 << nPackage
+ case *ast.ParenExpr:
+ return 1 << nParenExpr
+ case *ast.RangeStmt:
+ return 1 << nRangeStmt
+ case *ast.ReturnStmt:
+ return 1 << nReturnStmt
+ case *ast.SelectStmt:
+ return 1 << nSelectStmt
+ case *ast.SelectorExpr:
+ return 1 << nSelectorExpr
+ case *ast.SendStmt:
+ return 1 << nSendStmt
+ case *ast.SliceExpr:
+ return 1 << nSliceExpr
+ case *ast.StarExpr:
+ return 1 << nStarExpr
+ case *ast.StructType:
+ return 1 << nStructType
+ case *ast.SwitchStmt:
+ return 1 << nSwitchStmt
+ case *ast.TypeAssertExpr:
+ return 1 << nTypeAssertExpr
+ case *ast.TypeSpec:
+ return 1 << nTypeSpec
+ case *ast.TypeSwitchStmt:
+ return 1 << nTypeSwitchStmt
+ case *ast.UnaryExpr:
+ return 1 << nUnaryExpr
+ case *ast.ValueSpec:
+ return 1 << nValueSpec
+ }
+ return 0
+}
+
+func maskOf(nodes []ast.Node) uint64 {
+ if nodes == nil {
+ return 1<<64 - 1 // match all node types
+ }
+ var mask uint64
+ for _, n := range nodes {
+ mask |= typeOf(n)
+ }
+ return mask
+}
projects / dotfiles / .git / blobdiff