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ast.go
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ast.go
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package ast
import (
"path"
"strings"
)
// Every module (i.e. file) is parsed into a separate AST data structure. For
// efficiency, the parser also resolves all scopes and binds all symbols in the
// tree.
//
// Identifiers in the tree are referenced by a Ref, which is a pointer into the
// symbol table for the file. The symbol table is stored as a top-level field
// in the AST so it can be accessed without traversing the tree. For example,
// a renaming pass can iterate over the symbol table without touching the tree.
//
// Parse trees are intended to be immutable. That makes it easy to build an
// incremental compiler with a "watch" mode that can avoid re-parsing files
// that have already been parsed. Any passes that operate on an AST after it
// has been parsed should create a copy of the mutated parts of the tree
// instead of mutating the original tree.
type L int
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
const (
LLowest L = iota
LComma
LSpread
LYield
LAssign
LConditional
LNullishCoalescing
LLogicalOr
LLogicalAnd
LBitwiseOr
LBitwiseXor
LBitwiseAnd
LEquals
LCompare
LShift
LAdd
LMultiply
LExponentiation
LPrefix
LPostfix
LNew
LCall
)
type OpCode int
func (op OpCode) IsPrefix() bool {
return op < UnOpPostDec
}
func (op OpCode) IsUnaryUpdate() bool {
return op >= UnOpPreDec && op <= UnOpPostInc
}
func (op OpCode) IsLeftAssociative() bool {
return op >= BinOpAdd && op < BinOpComma && op != BinOpPow
}
func (op OpCode) IsRightAssociative() bool {
return op >= BinOpAssign || op == BinOpPow
}
// If you add a new token, remember to add it to "OpTable" too
const (
// Prefix
UnOpPos OpCode = iota
UnOpNeg
UnOpCpl
UnOpNot
UnOpVoid
UnOpTypeof
UnOpDelete
// Prefix update
UnOpPreDec
UnOpPreInc
// Postfix update
UnOpPostDec
UnOpPostInc
// Left-associative
BinOpAdd
BinOpSub
BinOpMul
BinOpDiv
BinOpRem
BinOpPow
BinOpLt
BinOpLe
BinOpGt
BinOpGe
BinOpIn
BinOpInstanceof
BinOpShl
BinOpShr
BinOpUShr
BinOpLooseEq
BinOpLooseNe
BinOpStrictEq
BinOpStrictNe
BinOpNullishCoalescing
BinOpLogicalOr
BinOpLogicalAnd
BinOpBitwiseOr
BinOpBitwiseAnd
BinOpBitwiseXor
// Non-associative
BinOpComma
// Right-associative
BinOpAssign
BinOpAddAssign
BinOpSubAssign
BinOpMulAssign
BinOpDivAssign
BinOpRemAssign
BinOpPowAssign
BinOpShlAssign
BinOpShrAssign
BinOpUShrAssign
BinOpBitwiseOrAssign
BinOpBitwiseAndAssign
BinOpBitwiseXorAssign
)
type opTableEntry struct {
Text string
Level L
IsKeyword bool
}
var OpTable = []opTableEntry{
// Prefix
{"+", LPrefix, false},
{"-", LPrefix, false},
{"~", LPrefix, false},
{"!", LPrefix, false},
{"void", LPrefix, true},
{"typeof", LPrefix, true},
{"delete", LPrefix, true},
// Prefix update
{"--", LPrefix, false},
{"++", LPrefix, false},
// Postfix update
{"--", LPostfix, false},
{"++", LPostfix, false},
// Left-associative
{"+", LAdd, false},
{"-", LAdd, false},
{"*", LMultiply, false},
{"/", LMultiply, false},
{"%", LMultiply, false},
{"**", LExponentiation, false}, // Right-associative
{"<", LCompare, false},
{"<=", LCompare, false},
{">", LCompare, false},
{">=", LCompare, false},
{"in", LCompare, true},
{"instanceof", LCompare, true},
{"<<", LShift, false},
{">>", LShift, false},
{">>>", LShift, false},
{"==", LEquals, false},
{"!=", LEquals, false},
{"===", LEquals, false},
{"!==", LEquals, false},
{"??", LNullishCoalescing, false},
{"||", LLogicalOr, false},
{"&&", LLogicalAnd, false},
{"|", LBitwiseOr, false},
{"&", LBitwiseAnd, false},
{"^", LBitwiseXor, false},
// Non-associative
{",", LComma, false},
// Right-associative
{"=", LAssign, false},
{"+=", LAssign, false},
{"-=", LAssign, false},
{"*=", LAssign, false},
{"/=", LAssign, false},
{"%=", LAssign, false},
{"**=", LAssign, false},
{"<<=", LAssign, false},
{">>=", LAssign, false},
{">>>=", LAssign, false},
{"|=", LAssign, false},
{"&=", LAssign, false},
{"^=", LAssign, false},
}
type Loc struct {
// This is the 0-based index of this location from the start of the file
Start int32
}
type Range struct {
Loc Loc
Len int32
}
type LocRef struct {
Loc Loc
Ref Ref
}
type Path struct {
Loc Loc
Text string
}
type PropertyKind int
const (
PropertyNormal PropertyKind = iota
PropertyGet
PropertySet
PropertySpread
)
type Property struct {
Kind PropertyKind
IsComputed bool
IsMethod bool
IsStatic bool
Key Expr
// This is omitted for class fields
Value *Expr
// This is used when parsing a pattern that uses default values:
//
// [a = 1] = [];
// ({a = 1} = {});
//
// It's also used for class fields:
//
// class Foo { a = 1 }
//
Initializer *Expr
}
type PropertyBinding struct {
IsComputed bool
IsSpread bool
Key Expr
Value Binding
DefaultValue *Expr
}
type Arg struct {
Binding Binding
Default *Expr
}
type Fn struct {
Name *LocRef
Args []Arg
IsAsync bool
IsGenerator bool
HasRestArg bool
Stmts []Stmt
}
type Class struct {
Name *LocRef
Extends *Expr
Properties []Property
}
type ArrayBinding struct {
Binding Binding
DefaultValue *Expr
}
type Binding struct {
Loc Loc
Data B
}
// This interface is never called. Its purpose is to encode a variant type in
// Go's type system.
type B interface{ isBinding() }
type BMissing struct{}
type BIdentifier struct{ Ref Ref }
type BArray struct {
Items []ArrayBinding
HasSpread bool
}
type BObject struct{ Properties []PropertyBinding }
func (*BMissing) isBinding() {}
func (*BIdentifier) isBinding() {}
func (*BArray) isBinding() {}
func (*BObject) isBinding() {}
type Expr struct {
Loc Loc
Data E
}
// This interface is never called. Its purpose is to encode a variant type in
// Go's type system.
type E interface{ isExpr() }
type EArray struct{ Items []Expr }
type EUnary struct {
Op OpCode
Value Expr
}
type EBinary struct {
Op OpCode
Left Expr
Right Expr
}
type EBoolean struct{ Value bool }
type ESuper struct{}
type ENull struct{}
type EUndefined struct{}
type EThis struct{}
type ENew struct {
Target Expr
Args []Expr
}
type ENewTarget struct{}
type EImportMeta struct{}
type ECall struct {
Target Expr
Args []Expr
IsOptionalChain bool
}
type EDot struct {
Target Expr
Name string
NameLoc Loc
IsOptionalChain bool
}
type EIndex struct {
Target Expr
Index Expr
IsOptionalChain bool
}
type EArrow struct {
IsAsync bool
Args []Arg
HasRestArg bool
Stmts []Stmt
Expr *Expr
}
type EFunction struct{ Fn Fn }
type EClass struct{ Class Class }
type EIdentifier struct{ Ref Ref }
type ENamespaceImport struct {
NamespaceRef Ref
ItemRef Ref
Alias string
}
type EJSXElement struct {
Tag *Expr
Properties []Property
Children []Expr
}
type EMissing struct{}
type ENumber struct{ Value float64 }
type EBigInt struct{ Value string }
type EObject struct{ Properties []Property }
type ESpread struct{ Value Expr }
type EString struct{ Value []uint16 }
type TemplatePart struct {
Value Expr
Tail []uint16
TailRaw string // This is only filled out for tagged template literals
}
type ETemplate struct {
Tag *Expr
Head []uint16
HeadRaw string // This is only filled out for tagged template literals
Parts []TemplatePart
}
type ERegExp struct{ Value string }
type EAwait struct {
Value Expr
}
type EYield struct {
Value *Expr
IsStar bool
}
type EIf struct {
Test Expr
Yes Expr
No Expr
}
type ERequire struct {
Path Path
IsES6Import bool
}
type EImport struct {
Expr Expr
}
func (*EArray) isExpr() {}
func (*EUnary) isExpr() {}
func (*EBinary) isExpr() {}
func (*EBoolean) isExpr() {}
func (*ESuper) isExpr() {}
func (*ENull) isExpr() {}
func (*EUndefined) isExpr() {}
func (*EThis) isExpr() {}
func (*ENew) isExpr() {}
func (*ENewTarget) isExpr() {}
func (*EImportMeta) isExpr() {}
func (*ECall) isExpr() {}
func (*EDot) isExpr() {}
func (*EIndex) isExpr() {}
func (*EArrow) isExpr() {}
func (*EFunction) isExpr() {}
func (*EClass) isExpr() {}
func (*EIdentifier) isExpr() {}
func (*ENamespaceImport) isExpr() {}
func (*EJSXElement) isExpr() {}
func (*EMissing) isExpr() {}
func (*ENumber) isExpr() {}
func (*EBigInt) isExpr() {}
func (*EObject) isExpr() {}
func (*ESpread) isExpr() {}
func (*EString) isExpr() {}
func (*ETemplate) isExpr() {}
func (*ERegExp) isExpr() {}
func (*EAwait) isExpr() {}
func (*EYield) isExpr() {}
func (*EIf) isExpr() {}
func (*ERequire) isExpr() {}
func (*EImport) isExpr() {}
type ExprOrStmt struct {
Expr *Expr
Stmt *Stmt
}
type Stmt struct {
Loc Loc
Data S
}
// This interface is never called. Its purpose is to encode a variant type in
// Go's type system.
type S interface{ isStmt() }
type SBlock struct {
Stmts []Stmt
}
type SEmpty struct{}
type SDebugger struct{}
type SDirective struct {
Value []uint16
}
type SExportClause struct {
Items []ClauseItem
}
type SExportFrom struct {
Items []ClauseItem
NamespaceRef Ref
Path Path
}
type SExportDefault struct {
DefaultName LocRef
Value ExprOrStmt // May be a SFunction or SClass
}
type SExportStar struct {
Item *ClauseItem
Path Path
}
type SExpr struct {
Value Expr
}
type SFunction struct {
Fn Fn
IsExport bool
}
type SClass struct {
Class Class
IsExport bool
}
type SLabel struct {
Name LocRef
Stmt Stmt
}
type SIf struct {
Test Expr
Yes Stmt
No *Stmt
}
type SFor struct {
Init *Stmt // May be a SConst, SLet, SVar, or SExpr
Test *Expr
Update *Expr
Body Stmt
}
type SForIn struct {
Init Stmt // May be a SConst, SLet, SVar, or SExpr
Value Expr
Body Stmt
}
type SForOf struct {
IsAwait bool
Init Stmt // May be a SConst, SLet, SVar, or SExpr
Value Expr
Body Stmt
}
type SDoWhile struct {
Body Stmt
Test Expr
}
type SWhile struct {
Test Expr
Body Stmt
}
type SWith struct {
Value Expr
Body Stmt
}
type Catch struct {
Loc Loc
Binding *Binding
Body []Stmt
}
type Finally struct {
Loc Loc
Stmts []Stmt
}
type STry struct {
Body []Stmt
Catch *Catch
Finally *Finally
}
type Case struct {
Value *Expr
Body []Stmt
}
type SSwitch struct {
Test Expr
Cases []Case
}
// This object represents all of these types of import statements:
//
// import 'path'
// import {item1, item2} from 'path'
// import * as ns from 'path'
// import defaultItem, {item1, item2} from 'path'
// import defaultItem, * as ns from 'path'
//
// Many parts are optional and can be combined in different ways. The only
// restriction is that you cannot have both a clause and a star namespace.
type SImport struct {
// If this is a star import: This is a Ref for the namespace symbol. The Loc
// for the symbol is StarLoc.
//
// Otherwise: This is an auto-generated Ref for the namespace representing
// the imported file. In this case StarLoc is nil. The NamespaceRef is used
// when converting this module to a CommonJS module.
NamespaceRef Ref
DefaultName *LocRef
Items *[]ClauseItem
StarLoc *Loc
Path Path
}
type SReturn struct {
Value *Expr
}
type SThrow struct {
Value Expr
}
type LocalKind uint8
const (
LocalVar LocalKind = iota
LocalLet
LocalConst
)
type SLocal struct {
Decls []Decl
Kind LocalKind
IsExport bool
}
type SBreak struct {
Name *LocRef
}
type SContinue struct {
Name *LocRef
}
func (*SBlock) isStmt() {}
func (*SDebugger) isStmt() {}
func (*SDirective) isStmt() {}
func (*SEmpty) isStmt() {}
func (*SExportClause) isStmt() {}
func (*SExportFrom) isStmt() {}
func (*SExportDefault) isStmt() {}
func (*SExportStar) isStmt() {}
func (*SExpr) isStmt() {}
func (*SFunction) isStmt() {}
func (*SClass) isStmt() {}
func (*SLabel) isStmt() {}
func (*SIf) isStmt() {}
func (*SFor) isStmt() {}
func (*SForIn) isStmt() {}
func (*SForOf) isStmt() {}
func (*SDoWhile) isStmt() {}
func (*SWhile) isStmt() {}
func (*SWith) isStmt() {}
func (*STry) isStmt() {}
func (*SSwitch) isStmt() {}
func (*SImport) isStmt() {}
func (*SReturn) isStmt() {}
func (*SThrow) isStmt() {}
func (*SLocal) isStmt() {}
func (*SBreak) isStmt() {}
func (*SContinue) isStmt() {}
type ClauseItem struct {
Alias string
AliasLoc Loc
Name LocRef
}
type Decl struct {
Binding Binding
Value *Expr
}
type SymbolKind uint8
const (
// An unbound symbol is one that isn't declared in the file it's referenced
// in. For example, using "window" without declaring it will be unbound.
SymbolUnbound SymbolKind = iota
// This has special merging behavior. You're allowed to re-declare these
// symbols more than once in the same scope. These symbols are also hoisted
// out of the scope they are declared in to the closest containing function
// or module scope. These are the symbols with this kind:
//
// - Function arguments
// - Function statements
// - Variables declared using "var"
//
SymbolHoisted
// There's a weird special case where catch variables declared using a simple
// identifier (i.e. not a binding pattern) block hoisted variables instead of
// becoming an error:
//
// var e = 0;
// try { throw 1 } catch (e) {
// print(e) // 1
// var e = 2
// print(e) // 2
// }
// print(e) // 0 (since the hoisting stops at the catch block boundary)
//
// However, other forms are still a syntax error:
//
// try {} catch (e) { let e }
// try {} catch ({e}) { var e }
//
// This symbol is for handling this weird special case.
SymbolCatchIdentifier
// This annotates all other symbols that don't have special behavior.
SymbolOther
)
var InvalidRef Ref = Ref{^uint32(0), ^uint32(0)}
// Files are parsed in parallel for speed. We want to allow each parser to
// generate symbol IDs that won't conflict with each other. We also want to be
// able to quickly merge symbol tables from all files into one giant symbol
// table.
//
// We can accomplish both goals by giving each symbol ID two parts: an outer
// index that is unique to the parser goroutine, and an inner index that
// increments as the parser generates new symbol IDs. Then a symbol map can
// be an array of arrays indexed first by outer index, then by inner index.
// The maps can be merged quickly by creating a single outer array containing
// all inner arrays from all parsed files.
type Ref struct {
OuterIndex uint32
InnerIndex uint32
}
type Symbol struct {
Kind SymbolKind
// An estimate of the number of uses of this symbol. This is used for
// minification (to prefer shorter names for more frequently used symbols).
// The reason why this is an estimate instead of an accurate count is that
// it's not updated during dead code elimination for speed. I figure that
// even without updating after parsing it's still a pretty good heuristic.
UseCountEstimate uint32
Name string
// Used by the parser for single pass parsing. Symbols that have been merged
// form a linked-list where the last link is the symbol to use. This link is
// an invalid ref if it's the last link. If this isn't invalid, you need to
// FollowSymbols to get the real one.
Link Ref
}
type ScopeKind int
const (
ScopeBlock ScopeKind = iota
ScopeLabel
ScopeFunction
ScopeFunctionName
ScopeClassName
ScopeModule
)
type Scope struct {
Kind ScopeKind
Parent *Scope
Children []*Scope
Members map[string]Ref
Generated []Ref
// This is used to store the ref of the label symbol for ScopeLabel scopes.
LabelRef Ref
}
type SymbolMap struct {
// This could be represented as a "map[Ref]Symbol" but a two-level array was
// more efficient in profiles. This appears to be because it doesn't involve
// a hash. This representation also makes it trivial to quickly merge symbol
// maps from multiple files together. Each file only generates symbols in a
// single inner array, so you can join the maps together by just make a
// single outer array containing all of the inner arrays. See the comment on
// "Ref" for more detail.
Outer [][]Symbol
}
func NewSymbolMap(maxSourceIndex int) *SymbolMap {
return &SymbolMap{make([][]Symbol, maxSourceIndex+1)}
}
func (sm *SymbolMap) Get(ref Ref) Symbol {
return sm.Outer[ref.OuterIndex][ref.InnerIndex]
}
func (sm *SymbolMap) IncrementUseCountEstimate(ref Ref) {
sm.Outer[ref.OuterIndex][ref.InnerIndex].UseCountEstimate++
}
// The symbol must already exist to call this
func (sm *SymbolMap) Set(ref Ref, symbol Symbol) {
sm.Outer[ref.OuterIndex][ref.InnerIndex] = symbol
}
// The symbol may not already exist when you call this
func (sm *SymbolMap) SetNew(ref Ref, symbol Symbol) {
outer := sm.Outer
inner := outer[ref.OuterIndex]
innerLen := uint32(len(inner))
if ref.InnerIndex >= innerLen {
inner = append(inner, make([]Symbol, ref.InnerIndex+1-innerLen)...)
outer[ref.OuterIndex] = inner
}
inner[ref.InnerIndex] = symbol
}
type ImportKind uint8
const (
ImportStmt ImportKind = iota
ImportRequire
ImportDynamic
)
type ImportPath struct {
Path Path
Kind ImportKind
}
type AST struct {
ImportPaths []ImportPath
// ENamespaceImport items in this map are printed as an indirect access off
// of the namespace. This is a way for the bundler to pass this information
// to the printer. This is necessary when using a namespace import or when
// an import item must be converted to a property access off a require() call.
IndirectImportItems map[Ref]bool
// This is true if something used the "exports" or "module" variables, which
// means they could have exported something. This is used to silence errors
// about mismatched exports.
HasCommonJsExports bool
Hashbang string
Stmts []Stmt
Symbols *SymbolMap
ModuleScope *Scope
ExportsRef Ref
RequireRef Ref
ModuleRef Ref
}
// Returns the canonical ref that represents the ref for the provided symbol.
// This may not be the provided ref if the symbol has been merged with another
// symbol.
func FollowSymbols(symbols *SymbolMap, ref Ref) Ref {
symbol := symbols.Get(ref)
if symbol.Link == InvalidRef {
return ref
}
link := FollowSymbols(symbols, symbol.Link)
// Only write if needed to avoid concurrent map update hazards
if symbol.Link != link {
symbol.Link = link
symbols.Set(ref, symbol)
}
return link
}
// Use this before calling "FollowSymbols" from separate threads to avoid
// concurrent map update hazards. In Go, mutating a map is not threadsafe
// but reading from a map is. Calling "FollowAllSymbols" first ensures that
// all mutation is done up front.
func FollowAllSymbols(symbols *SymbolMap) {
for sourceIndex, inner := range symbols.Outer {
for symbolIndex, _ := range inner {
FollowSymbols(symbols, Ref{uint32(sourceIndex), uint32(symbolIndex)})
}
}
}
// Makes "old" point to "new" by joining the linked lists for the two symbols
// together. That way "FollowSymbols" on both "old" and "new" will result in
// the same ref.
func MergeSymbols(symbols *SymbolMap, old Ref, new Ref) Ref {
if old == new {
return new
}
oldSymbol := symbols.Get(old)
if oldSymbol.Link != InvalidRef {
oldSymbol.Link = MergeSymbols(symbols, oldSymbol.Link, new)
symbols.Set(old, oldSymbol)
return oldSymbol.Link
}
newSymbol := symbols.Get(new)
if newSymbol.Link != InvalidRef {
newSymbol.Link = MergeSymbols(symbols, old, newSymbol.Link)
symbols.Set(new, newSymbol)
return newSymbol.Link
}
oldSymbol.Link = new
newSymbol.UseCountEstimate += oldSymbol.UseCountEstimate
symbols.Set(old, oldSymbol)
symbols.Set(new, newSymbol)
return new
}
func GenerateNonUniqueNameFromPath(text string) string {
// Get the file name without the extension
base := path.Base(text)
lastDot := strings.LastIndexByte(base, '.')
if lastDot >= 0 {
base = base[:lastDot]
}
// Convert it to an ASCII identifier
bytes := []byte{}
for _, c := range base {
if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (len(bytes) > 0 && c >= '0' && c <= '9') {
bytes = append(bytes, byte(c))
} else if len(bytes) > 0 && bytes[len(bytes)-1] != '_' {
bytes = append(bytes, '_')
}
}
// Make sure the name isn't empty
if len(bytes) == 0 {
return "_"
}
return string(bytes)
}