import "go/ast"
Package ast declares the types used to represent syntax trees for Go packages.
func FileExports(src *File) bool
FileExports trims the AST for a Go source file in place such that only exported nodes remain: all top-level identifiers which are not exported and their associated information (such as type, initial value, or function body) are removed. Non-exported fields and methods of exported types are stripped. The File.Comments list is not changed.
FileExports reports whether there are exported declarations.
func FilterDecl(decl Decl, f Filter) bool
FilterDecl trims the AST for a Go declaration in place by removing all names (including struct field and interface method names, but not from parameter lists) that don't pass through the filter f.
FilterDecl reports whether there are any declared names left after filtering.
func FilterFile(src *File, f Filter) bool
FilterFile trims the AST for a Go file in place by removing all names from top-level declarations (including struct field and interface method names, but not from parameter lists) that don't pass through the filter f. If the declaration is empty afterwards, the declaration is removed from the AST. Import declarations are always removed. The File.Comments list is not changed.
FilterFile reports whether there are any top-level declarations left after filtering.
func FilterPackage(pkg *Package, f Filter) bool
FilterPackage trims the AST for a Go package in place by removing all names from top-level declarations (including struct field and interface method names, but not from parameter lists) that don't pass through the filter f. If the declaration is empty afterwards, the declaration is removed from the AST. The pkg.Files list is not changed, so that file names and top-level package comments don't get lost.
FilterPackage reports whether there are any top-level declarations left after filtering.
func Fprint(w io.Writer, fset *token.FileSet, x interface{}, f FieldFilter) error
Fprint prints the (sub-)tree starting at AST node x to w. If fset != nil, position information is interpreted relative to that file set. Otherwise positions are printed as integer values (file set specific offsets).
A non-nil FieldFilter f may be provided to control the output: struct fields for which f(fieldname, fieldvalue) is true are printed; all others are filtered from the output. Unexported struct fields are never printed.
func Inspect(node Node, f func(Node) bool)
Inspect traverses an AST in depth-first order: It starts by calling f(node); node must not be nil. If f returns true, Inspect invokes f recursively for each of the non-nil children of node, followed by a call of f(nil).
This example demonstrates how to inspect the AST of a Go program.
Code:
// src is the input for which we want to inspect the AST. src := ` package p const c = 1.0 var X = f(3.14)*2 + c ` // Create the AST by parsing src. fset := token.NewFileSet() // positions are relative to fset f, err := parser.ParseFile(fset, "src.go", src, 0) if err != nil { panic(err) } // Inspect the AST and print all identifiers and literals. ast.Inspect(f, func(n ast.Node) bool { var s string switch x := n.(type) { case *ast.BasicLit: s = x.Value case *ast.Ident: s = x.Name } if s != "" { fmt.Printf("%s:\t%s\n", fset.Position(n.Pos()), s) } return true })
Output:
src.go:2:9: p src.go:3:7: c src.go:3:11: 1.0 src.go:4:5: X src.go:4:9: f src.go:4:11: 3.14 src.go:4:17: 2 src.go:4:21: c
func IsExported(name string) bool
IsExported reports whether name starts with an upper-case letter.
func NotNilFilter(_ string, v reflect.Value) bool
NotNilFilter returns true for field values that are not nil; it returns false otherwise.
func PackageExports(pkg *Package) bool
PackageExports trims the AST for a Go package in place such that only exported nodes remain. The pkg.Files list is not changed, so that file names and top-level package comments don't get lost.
PackageExports reports whether there are exported declarations; it returns false otherwise.
func Print(fset *token.FileSet, x interface{}) error
Print prints x to standard output, skipping nil fields. Print(fset, x) is the same as Fprint(os.Stdout, fset, x, NotNilFilter).
This example shows what an AST looks like when printed for debugging.
Code:
// src is the input for which we want to print the AST. src := ` package main func main() { println("Hello, World!") } ` // Create the AST by parsing src. fset := token.NewFileSet() // positions are relative to fset f, err := parser.ParseFile(fset, "", src, 0) if err != nil { panic(err) } // Print the AST. ast.Print(fset, f)
Output:
0 *ast.File {
1 . Package: 2:1
2 . Name: *ast.Ident {
3 . . NamePos: 2:9
4 . . Name: "main"
5 . }
6 . Decls: []ast.Decl (len = 1) {
7 . . 0: *ast.FuncDecl {
8 . . . Name: *ast.Ident {
9 . . . . NamePos: 3:6
10 . . . . Name: "main"
11 . . . . Obj: *ast.Object {
12 . . . . . Kind: func
13 . . . . . Name: "main"
14 . . . . . Decl: *(obj @ 7)
15 . . . . }
16 . . . }
17 . . . Type: *ast.FuncType {
18 . . . . Func: 3:1
19 . . . . Params: *ast.FieldList {
20 . . . . . Opening: 3:10
21 . . . . . Closing: 3:11
22 . . . . }
23 . . . }
24 . . . Body: *ast.BlockStmt {
25 . . . . Lbrace: 3:13
26 . . . . List: []ast.Stmt (len = 1) {
27 . . . . . 0: *ast.ExprStmt {
28 . . . . . . X: *ast.CallExpr {
29 . . . . . . . Fun: *ast.Ident {
30 . . . . . . . . NamePos: 4:2
31 . . . . . . . . Name: "println"
32 . . . . . . . }
33 . . . . . . . Lparen: 4:9
34 . . . . . . . Args: []ast.Expr (len = 1) {
35 . . . . . . . . 0: *ast.BasicLit {
36 . . . . . . . . . ValuePos: 4:10
37 . . . . . . . . . Kind: STRING
38 . . . . . . . . . Value: "\"Hello, World!\""
39 . . . . . . . . }
40 . . . . . . . }
41 . . . . . . . Ellipsis: -
42 . . . . . . . Rparen: 4:25
43 . . . . . . }
44 . . . . . }
45 . . . . }
46 . . . . Rbrace: 5:1
47 . . . }
48 . . }
49 . }
50 . Scope: *ast.Scope {
51 . . Objects: map[string]*ast.Object (len = 1) {
52 . . . "main": *(obj @ 11)
53 . . }
54 . }
55 . Unresolved: []*ast.Ident (len = 1) {
56 . . 0: *(obj @ 29)
57 . }
58 }
func SortImports(fset *token.FileSet, f *File)
SortImports sorts runs of consecutive import lines in import blocks in f. It also removes duplicate imports when it is possible to do so without data loss.
func Walk(v Visitor, node Node)
Walk traverses an AST in depth-first order: It starts by calling v.Visit(node); node must not be nil. If the visitor w returned by v.Visit(node) is not nil, Walk is invoked recursively with visitor w for each of the non-nil children of node, followed by a call of w.Visit(nil).
type ArrayType struct {
Lbrack token.Pos // position of "["
Len Expr // Ellipsis node for [...]T array types, nil for slice types
Elt Expr // element type
}
An ArrayType node represents an array or slice type.
func (x *ArrayType) End() token.Pos
func (x *ArrayType) Pos() token.Pos
type AssignStmt struct {
Lhs []Expr
TokPos token.Pos // position of Tok
Tok token.Token // assignment token, DEFINE
Rhs []Expr
}
An AssignStmt node represents an assignment or a short variable declaration.
func (s *AssignStmt) End() token.Pos
func (s *AssignStmt) Pos() token.Pos
type BadDecl struct {
From, To token.Pos // position range of bad declaration
}
A BadDecl node is a placeholder for declarations containing syntax errors for which no correct declaration nodes can be created.
func (d *BadDecl) End() token.Pos
func (d *BadDecl) Pos() token.Pos
type BadExpr struct {
From, To token.Pos // position range of bad expression
}
A BadExpr node is a placeholder for expressions containing syntax errors for which no correct expression nodes can be created.
func (x *BadExpr) End() token.Pos
func (x *BadExpr) Pos() token.Pos
type BadStmt struct {
From, To token.Pos // position range of bad statement
}
A BadStmt node is a placeholder for statements containing syntax errors for which no correct statement nodes can be created.
func (s *BadStmt) End() token.Pos
func (s *BadStmt) Pos() token.Pos
type BasicLit struct {
ValuePos token.Pos // literal position
Kind token.Token // token.INT, token.FLOAT, token.IMAG, token.CHAR, or token.STRING
Value string // literal string; e.g. 42, 0x7f, 3.14, 1e-9, 2.4i, 'a', '\x7f', "foo" or `\m\n\o`
}
A BasicLit node represents a literal of basic type.
func (x *BasicLit) End() token.Pos
func (x *BasicLit) Pos() token.Pos
type BinaryExpr struct {
X Expr // left operand
OpPos token.Pos // position of Op
Op token.Token // operator
Y Expr // right operand
}
A BinaryExpr node represents a binary expression.
func (x *BinaryExpr) End() token.Pos
func (x *BinaryExpr) Pos() token.Pos
type BlockStmt struct {
Lbrace token.Pos // position of "{"
List []Stmt
Rbrace token.Pos // position of "}"
}
A BlockStmt node represents a braced statement list.
func (s *BlockStmt) End() token.Pos
func (s *BlockStmt) Pos() token.Pos
type BranchStmt struct {
TokPos token.Pos // position of Tok
Tok token.Token // keyword token (BREAK, CONTINUE, GOTO, FALLTHROUGH)
Label *Ident // label name; or nil
}
A BranchStmt node represents a break, continue, goto, or fallthrough statement.
func (s *BranchStmt) End() token.Pos
func (s *BranchStmt) Pos() token.Pos
type CallExpr struct {
Fun Expr // function expression
Lparen token.Pos // position of "("
Args []Expr // function arguments; or nil
Ellipsis token.Pos // position of "..." (token.NoPos if there is no "...")
Rparen token.Pos // position of ")"
}
A CallExpr node represents an expression followed by an argument list.
func (x *CallExpr) End() token.Pos
func (x *CallExpr) Pos() token.Pos
type CaseClause struct {
Case token.Pos // position of "case" or "default" keyword
List []Expr // list of expressions or types; nil means default case
Colon token.Pos // position of ":"
Body []Stmt // statement list; or nil
}
A CaseClause represents a case of an expression or type switch statement.
func (s *CaseClause) End() token.Pos
func (s *CaseClause) Pos() token.Pos
type ChanDir int
The direction of a channel type is indicated by a bit mask including one or both of the following constants.
const (
SEND ChanDir = 1 << iota
RECV
)
type ChanType struct {
Begin token.Pos // position of "chan" keyword or "<-" (whichever comes first)
Arrow token.Pos // position of "<-" (token.NoPos if there is no "<-")
Dir ChanDir // channel direction
Value Expr // value type
}
A ChanType node represents a channel type.
func (x *ChanType) End() token.Pos
func (x *ChanType) Pos() token.Pos
type CommClause struct {
Case token.Pos // position of "case" or "default" keyword
Comm Stmt // send or receive statement; nil means default case
Colon token.Pos // position of ":"
Body []Stmt // statement list; or nil
}
A CommClause node represents a case of a select statement.
func (s *CommClause) End() token.Pos
func (s *CommClause) Pos() token.Pos
type Comment struct {
Slash token.Pos // position of "/" starting the comment
Text string // comment text (excluding '\n' for //-style comments)
}
A Comment node represents a single //-style or /*-style comment.
func (c *Comment) End() token.Pos
func (c *Comment) Pos() token.Pos
type CommentGroup struct {
List []*Comment // len(List) > 0
}
A CommentGroup represents a sequence of comments with no other tokens and no empty lines between.
func (g *CommentGroup) End() token.Pos
func (g *CommentGroup) Pos() token.Pos
func (g *CommentGroup) Text() string
Text returns the text of the comment. Comment markers (//, /*, and */), the first space of a line comment, and leading and trailing empty lines are removed. Multiple empty lines are reduced to one, and trailing space on lines is trimmed. Unless the result is empty, it is newline-terminated.
type CommentMap map[Node][]*CommentGroup
A CommentMap maps an AST node to a list of comment groups associated with it. See NewCommentMap for a description of the association.
This example illustrates how to remove a variable declaration in a Go program while maintaining correct comment association using an ast.CommentMap.
Code:
// src is the input for which we create the AST that we // are going to manipulate. src := ` // This is the package comment. package main // This comment is associated with the hello constant. const hello = "Hello, World!" // line comment 1 // This comment is associated with the foo variable. var foo = hello // line comment 2 // This comment is associated with the main function. func main() { fmt.Println(hello) // line comment 3 } ` // Create the AST by parsing src. fset := token.NewFileSet() // positions are relative to fset f, err := parser.ParseFile(fset, "src.go", src, parser.ParseComments) if err != nil { panic(err) } // Create an ast.CommentMap from the ast.File's comments. // This helps keeping the association between comments // and AST nodes. cmap := ast.NewCommentMap(fset, f, f.Comments) // Remove the first variable declaration from the list of declarations. for i, decl := range f.Decls { if gen, ok := decl.(*ast.GenDecl); ok && gen.Tok == token.VAR { copy(f.Decls[i:], f.Decls[i+1:]) f.Decls = f.Decls[:len(f.Decls)-1] break } } // Use the comment map to filter comments that don't belong anymore // (the comments associated with the variable declaration), and create // the new comments list. f.Comments = cmap.Filter(f).Comments() // Print the modified AST. var buf bytes.Buffer if err := format.Node(&buf, fset, f); err != nil { panic(err) } fmt.Printf("%s", buf.Bytes())
Output:
// This is the package comment.
package main
// This comment is associated with the hello constant.
const hello = "Hello, World!" // line comment 1
// This comment is associated with the main function.
func main() {
fmt.Println(hello) // line comment 3
}
func NewCommentMap(fset *token.FileSet, node Node, comments []*CommentGroup) CommentMap
NewCommentMap creates a new comment map by associating comment groups of the comments list with the nodes of the AST specified by node.
A comment group g is associated with a node n if:
- g starts on the same line as n ends - g starts on the line immediately following n, and there is at least one empty line after g and before the next node - g starts before n and is not associated to the node before n via the previous rules
NewCommentMap tries to associate a comment group to the "largest" node possible: For instance, if the comment is a line comment trailing an assignment, the comment is associated with the entire assignment rather than just the last operand in the assignment.
func (cmap CommentMap) Comments() []*CommentGroup
Comments returns the list of comment groups in the comment map. The result is sorted in source order.
func (cmap CommentMap) Filter(node Node) CommentMap
Filter returns a new comment map consisting of only those entries of cmap for which a corresponding node exists in the AST specified by node.
func (cmap CommentMap) String() string
func (cmap CommentMap) Update(old, new Node) Node
Update replaces an old node in the comment map with the new node and returns the new node. Comments that were associated with the old node are associated with the new node.
type CompositeLit struct {
Type Expr // literal type; or nil
Lbrace token.Pos // position of "{"
Elts []Expr // list of composite elements; or nil
Rbrace token.Pos // position of "}"
Incomplete bool // true if (source) expressions are missing in the Elts list
}
A CompositeLit node represents a composite literal.
func (x *CompositeLit) End() token.Pos
func (x *CompositeLit) Pos() token.Pos
type Decl interface {
Node
// contains filtered or unexported methods
}
All declaration nodes implement the Decl interface.
type DeclStmt struct {
Decl Decl // *GenDecl with CONST, TYPE, or VAR token
}
A DeclStmt node represents a declaration in a statement list.
func (s *DeclStmt) End() token.Pos
func (s *DeclStmt) Pos() token.Pos
type DeferStmt struct {
Defer token.Pos // position of "defer" keyword
Call *CallExpr
}
A DeferStmt node represents a defer statement.
func (s *DeferStmt) End() token.Pos
func (s *DeferStmt) Pos() token.Pos
type Ellipsis struct {
Ellipsis token.Pos // position of "..."
Elt Expr // ellipsis element type (parameter lists only); or nil
}
An Ellipsis node stands for the "..." type in a parameter list or the "..." length in an array type.
func (x *Ellipsis) End() token.Pos
func (x *Ellipsis) Pos() token.Pos
type EmptyStmt struct {
Semicolon token.Pos // position of following ";"
Implicit bool // if set, ";" was omitted in the source
}
An EmptyStmt node represents an empty statement. The "position" of the empty statement is the position of the immediately following (explicit or implicit) semicolon.
func (s *EmptyStmt) End() token.Pos
func (s *EmptyStmt) Pos() token.Pos
type Expr interface {
Node
// contains filtered or unexported methods
}
All expression nodes implement the Expr interface.
type ExprStmt struct {
X Expr // expression
}
An ExprStmt node represents a (stand-alone) expression in a statement list.
func (s *ExprStmt) End() token.Pos
func (s *ExprStmt) Pos() token.Pos
type Field struct {
Doc *CommentGroup // associated documentation; or nil
Names []*Ident // field/method/parameter names; or nil
Type Expr // field/method/parameter type
Tag *BasicLit // field tag; or nil
Comment *CommentGroup // line comments; or nil
}
A Field represents a Field declaration list in a struct type, a method list in an interface type, or a parameter/result declaration in a signature. Field.Names is nil for unnamed parameters (parameter lists which only contain types) and embedded struct fields. In the latter case, the field name is the type name.
func (f *Field) End() token.Pos
func (f *Field) Pos() token.Pos
type FieldFilter func(name string, value reflect.Value) bool
A FieldFilter may be provided to Fprint to control the output.
type FieldList struct {
Opening token.Pos // position of opening parenthesis/brace, if any
List []*Field // field list; or nil
Closing token.Pos // position of closing parenthesis/brace, if any
}
A FieldList represents a list of Fields, enclosed by parentheses or braces.
func (f *FieldList) End() token.Pos
func (f *FieldList) NumFields() int
NumFields returns the number of parameters or struct fields represented by a FieldList.
func (f *FieldList) Pos() token.Pos
type File struct {
Doc *CommentGroup // associated documentation; or nil
Package token.Pos // position of "package" keyword
Name *Ident // package name
Decls []Decl // top-level declarations; or nil
Scope *Scope // package scope (this file only)
Imports []*ImportSpec // imports in this file
Unresolved []*Ident // unresolved identifiers in this file
Comments []*CommentGroup // list of all comments in the source file
}
A File node represents a Go source file.
The Comments list contains all comments in the source file in order of appearance, including the comments that are pointed to from other nodes via Doc and Comment fields.
For correct printing of source code containing comments (using packages go/format and go/printer), special care must be taken to update comments when a File's syntax tree is modified: For printing, comments are interspersed between tokens based on their position. If syntax tree nodes are removed or moved, relevant comments in their vicinity must also be removed (from the File.Comments list) or moved accordingly (by updating their positions). A CommentMap may be used to facilitate some of these operations.
Whether and how a comment is associated with a node depends on the interpretation of the syntax tree by the manipulating program: Except for Doc and Comment comments directly associated with nodes, the remaining comments are "free-floating" (see also issues #18593, #20744).
func MergePackageFiles(pkg *Package, mode MergeMode) *File
MergePackageFiles creates a file AST by merging the ASTs of the files belonging to a package. The mode flags control merging behavior.
func (f *File) End() token.Pos
func (f *File) Pos() token.Pos
type Filter func(string) bool
type ForStmt struct {
For token.Pos // position of "for" keyword
Init Stmt // initialization statement; or nil
Cond Expr // condition; or nil
Post Stmt // post iteration statement; or nil
Body *BlockStmt
}
A ForStmt represents a for statement.
func (s *ForStmt) End() token.Pos
func (s *ForStmt) Pos() token.Pos
type FuncDecl struct {
Doc *CommentGroup // associated documentation; or nil
Recv *FieldList // receiver (methods); or nil (functions)
Name *Ident // function/method name
Type *FuncType // function signature: parameters, results, and position of "func" keyword
Body *BlockStmt // function body; or nil for external (non-Go) function
}
A FuncDecl node represents a function declaration.
func (d *FuncDecl) End() token.Pos
func (d *FuncDecl) Pos() token.Pos
type FuncLit struct {
Type *FuncType // function type
Body *BlockStmt // function body
}
A FuncLit node represents a function literal.
func (x *FuncLit) End() token.Pos
func (x *FuncLit) Pos() token.Pos
type FuncType struct {
Func token.Pos // position of "func" keyword (token.NoPos if there is no "func")
Params *FieldList // (incoming) parameters; non-nil
Results *FieldList // (outgoing) results; or nil
}
A FuncType node represents a function type.
func (x *FuncType) End() token.Pos
func (x *FuncType) Pos() token.Pos
type GenDecl struct {
Doc *CommentGroup // associated documentation; or nil
TokPos token.Pos // position of Tok
Tok token.Token // IMPORT, CONST, TYPE, VAR
Lparen token.Pos // position of '(', if any
Specs []Spec
Rparen token.Pos // position of ')', if any
}
A GenDecl node (generic declaration node) represents an import, constant, type or variable declaration. A valid Lparen position (Lparen.IsValid()) indicates a parenthesized declaration.
Relationship between Tok value and Specs element type:
token.IMPORT *ImportSpec token.CONST *ValueSpec token.TYPE *TypeSpec token.VAR *ValueSpec
func (d *GenDecl) End() token.Pos
func (d *GenDecl) Pos() token.Pos
type GoStmt struct {
Go token.Pos // position of "go" keyword
Call *CallExpr
}
A GoStmt node represents a go statement.
func (s *GoStmt) End() token.Pos
func (s *GoStmt) Pos() token.Pos
type Ident struct {
NamePos token.Pos // identifier position
Name string // identifier name
Obj *Object // denoted object; or nil
}
An Ident node represents an identifier.
func NewIdent(name string) *Ident
NewIdent creates a new Ident without position. Useful for ASTs generated by code other than the Go parser.
func (x *Ident) End() token.Pos
func (id *Ident) IsExported() bool
IsExported reports whether id starts with an upper-case letter.
func (x *Ident) Pos() token.Pos
func (id *Ident) String() string
type IfStmt struct {
If token.Pos // position of "if" keyword
Init Stmt // initialization statement; or nil
Cond Expr // condition
Body *BlockStmt
Else Stmt // else branch; or nil
}
An IfStmt node represents an if statement.
func (s *IfStmt) End() token.Pos
func (s *IfStmt) Pos() token.Pos
type ImportSpec struct {
Doc *CommentGroup // associated documentation; or nil
Name *Ident // local package name (including "."); or nil
Path *BasicLit // import path
Comment *CommentGroup // line comments; or nil
EndPos token.Pos // end of spec (overrides Path.Pos if nonzero)
}
An ImportSpec node represents a single package import.
func (s *ImportSpec) End() token.Pos
func (s *ImportSpec) Pos() token.Pos
type Importer func(imports map[string]*Object, path string) (pkg *Object, err error)
An Importer resolves import paths to package Objects. The imports map records the packages already imported, indexed by package id (canonical import path). An Importer must determine the canonical import path and check the map to see if it is already present in the imports map. If so, the Importer can return the map entry. Otherwise, the Importer should load the package data for the given path into a new *Object (pkg), record pkg in the imports map, and then return pkg.
type IncDecStmt struct {
X Expr
TokPos token.Pos // position of Tok
Tok token.Token // INC or DEC
}
An IncDecStmt node represents an increment or decrement statement.
func (s *IncDecStmt) End() token.Pos
func (s *IncDecStmt) Pos() token.Pos
type IndexExpr struct {
X Expr // expression
Lbrack token.Pos // position of "["
Index Expr // index expression
Rbrack token.Pos // position of "]"
}
An IndexExpr node represents an expression followed by an index.
func (x *IndexExpr) End() token.Pos
func (x *IndexExpr) Pos() token.Pos
type InterfaceType struct {
Interface token.Pos // position of "interface" keyword
Methods *FieldList // list of methods
Incomplete bool // true if (source) methods are missing in the Methods list
}
An InterfaceType node represents an interface type.
func (x *InterfaceType) End() token.Pos
func (x *InterfaceType) Pos() token.Pos
type KeyValueExpr struct {
Key Expr
Colon token.Pos // position of ":"
Value Expr
}
A KeyValueExpr node represents (key : value) pairs in composite literals.
func (x *KeyValueExpr) End() token.Pos
func (x *KeyValueExpr) Pos() token.Pos
type LabeledStmt struct {
Label *Ident
Colon token.Pos // position of ":"
Stmt Stmt
}
A LabeledStmt node represents a labeled statement.
func (s *LabeledStmt) End() token.Pos
func (s *LabeledStmt) Pos() token.Pos
type MapType struct {
Map token.Pos // position of "map" keyword
Key Expr
Value Expr
}
A MapType node represents a map type.
func (x *MapType) End() token.Pos
func (x *MapType) Pos() token.Pos
type MergeMode uint
The MergeMode flags control the behavior of MergePackageFiles.
const (
// If set, duplicate function declarations are excluded.
FilterFuncDuplicates MergeMode = 1 << iota
// If set, comments that are not associated with a specific
// AST node (as Doc or Comment) are excluded.
FilterUnassociatedComments
// If set, duplicate import declarations are excluded.
FilterImportDuplicates
)
type Node interface {
Pos() token.Pos // position of first character belonging to the node
End() token.Pos // position of first character immediately after the node
}
All node types implement the Node interface.
type ObjKind int
ObjKind describes what an object represents.
const (
Bad ObjKind = iota // for error handling
Pkg // package
Con // constant
Typ // type
Var // variable
Fun // function or method
Lbl // label
)
The list of possible Object kinds.
func (kind ObjKind) String() string
type Object struct {
Kind ObjKind
Name string // declared name
Decl interface{} // corresponding Field, XxxSpec, FuncDecl, LabeledStmt, AssignStmt, Scope; or nil
Data interface{} // object-specific data; or nil
Type interface{} // placeholder for type information; may be nil
}
An Object describes a named language entity such as a package, constant, type, variable, function (incl. methods), or label.
The Data fields contains object-specific data:
Kind Data type Data value Pkg *Scope package scope Con int iota for the respective declaration
func NewObj(kind ObjKind, name string) *Object
NewObj creates a new object of a given kind and name.
func (obj *Object) Pos() token.Pos
Pos computes the source position of the declaration of an object name. The result may be an invalid position if it cannot be computed (obj.Decl may be nil or not correct).
type Package struct {
Name string // package name
Scope *Scope // package scope across all files
Imports map[string]*Object // map of package id -> package object
Files map[string]*File // Go source files by filename
}
A Package node represents a set of source files collectively building a Go package.
func NewPackage(fset *token.FileSet, files map[string]*File, importer Importer, universe *Scope) (*Package, error)
NewPackage creates a new Package node from a set of File nodes. It resolves unresolved identifiers across files and updates each file's Unresolved list accordingly. If a non-nil importer and universe scope are provided, they are used to resolve identifiers not declared in any of the package files. Any remaining unresolved identifiers are reported as undeclared. If the files belong to different packages, one package name is selected and files with different package names are reported and then ignored. The result is a package node and a scanner.ErrorList if there were errors.
func (p *Package) End() token.Pos
func (p *Package) Pos() token.Pos
type ParenExpr struct {
Lparen token.Pos // position of "("
X Expr // parenthesized expression
Rparen token.Pos // position of ")"
}
A ParenExpr node represents a parenthesized expression.
func (x *ParenExpr) End() token.Pos
func (x *ParenExpr) Pos() token.Pos
type RangeStmt struct {
For token.Pos // position of "for" keyword
Key, Value Expr // Key, Value may be nil
TokPos token.Pos // position of Tok; invalid if Key == nil
Tok token.Token // ILLEGAL if Key == nil, ASSIGN, DEFINE
X Expr // value to range over
Body *BlockStmt
}
A RangeStmt represents a for statement with a range clause.
func (s *RangeStmt) End() token.Pos
func (s *RangeStmt) Pos() token.Pos
type ReturnStmt struct {
Return token.Pos // position of "return" keyword
Results []Expr // result expressions; or nil
}
A ReturnStmt node represents a return statement.
func (s *ReturnStmt) End() token.Pos
func (s *ReturnStmt) Pos() token.Pos
type Scope struct {
Outer *Scope
Objects map[string]*Object
}
A Scope maintains the set of named language entities declared in the scope and a link to the immediately surrounding (outer) scope.
func NewScope(outer *Scope) *Scope
NewScope creates a new scope nested in the outer scope.
func (s *Scope) Insert(obj *Object) (alt *Object)
Insert attempts to insert a named object obj into the scope s. If the scope already contains an object alt with the same name, Insert leaves the scope unchanged and returns alt. Otherwise it inserts obj and returns nil.
func (s *Scope) Lookup(name string) *Object
Lookup returns the object with the given name if it is found in scope s, otherwise it returns nil. Outer scopes are ignored.
func (s *Scope) String() string
Debugging support
type SelectStmt struct {
Select token.Pos // position of "select" keyword
Body *BlockStmt // CommClauses only
}
An SelectStmt node represents a select statement.
func (s *SelectStmt) End() token.Pos
func (s *SelectStmt) Pos() token.Pos
type SelectorExpr struct {
X Expr // expression
Sel *Ident // field selector
}
A SelectorExpr node represents an expression followed by a selector.
func (x *SelectorExpr) End() token.Pos
func (x *SelectorExpr) Pos() token.Pos
type SendStmt struct {
Chan Expr
Arrow token.Pos // position of "<-"
Value Expr
}
A SendStmt node represents a send statement.
func (s *SendStmt) End() token.Pos
func (s *SendStmt) Pos() token.Pos
type SliceExpr struct {
X Expr // expression
Lbrack token.Pos // position of "["
Low Expr // begin of slice range; or nil
High Expr // end of slice range; or nil
Max Expr // maximum capacity of slice; or nil
Slice3 bool // true if 3-index slice (2 colons present)
Rbrack token.Pos // position of "]"
}
An SliceExpr node represents an expression followed by slice indices.
func (x *SliceExpr) End() token.Pos
func (x *SliceExpr) Pos() token.Pos
type Spec interface {
Node
// contains filtered or unexported methods
}
The Spec type stands for any of *ImportSpec, *ValueSpec, and *TypeSpec.
type StarExpr struct {
Star token.Pos // position of "*"
X Expr // operand
}
A StarExpr node represents an expression of the form "*" Expression. Semantically it could be a unary "*" expression, or a pointer type.
func (x *StarExpr) End() token.Pos
func (x *StarExpr) Pos() token.Pos
type Stmt interface {
Node
// contains filtered or unexported methods
}
All statement nodes implement the Stmt interface.
type StructType struct {
Struct token.Pos // position of "struct" keyword
Fields *FieldList // list of field declarations
Incomplete bool // true if (source) fields are missing in the Fields list
}
A StructType node represents a struct type.
func (x *StructType) End() token.Pos
func (x *StructType) Pos() token.Pos
type SwitchStmt struct {
Switch token.Pos // position of "switch" keyword
Init Stmt // initialization statement; or nil
Tag Expr // tag expression; or nil
Body *BlockStmt // CaseClauses only
}
A SwitchStmt node represents an expression switch statement.
func (s *SwitchStmt) End() token.Pos
func (s *SwitchStmt) Pos() token.Pos
type TypeAssertExpr struct {
X Expr // expression
Lparen token.Pos // position of "("
Type Expr // asserted type; nil means type switch X.(type)
Rparen token.Pos // position of ")"
}
A TypeAssertExpr node represents an expression followed by a type assertion.
func (x *TypeAssertExpr) End() token.Pos
func (x *TypeAssertExpr) Pos() token.Pos
type TypeSpec struct {
Doc *CommentGroup // associated documentation; or nil
Name *Ident // type name
Assign token.Pos // position of '=', if any
Type Expr // *Ident, *ParenExpr, *SelectorExpr, *StarExpr, or any of the *XxxTypes
Comment *CommentGroup // line comments; or nil
}
A TypeSpec node represents a type declaration (TypeSpec production).
func (s *TypeSpec) End() token.Pos
func (s *TypeSpec) Pos() token.Pos
type TypeSwitchStmt struct {
Switch token.Pos // position of "switch" keyword
Init Stmt // initialization statement; or nil
Assign Stmt // x := y.(type) or y.(type)
Body *BlockStmt // CaseClauses only
}
An TypeSwitchStmt node represents a type switch statement.
func (s *TypeSwitchStmt) End() token.Pos
func (s *TypeSwitchStmt) Pos() token.Pos
type UnaryExpr struct {
OpPos token.Pos // position of Op
Op token.Token // operator
X Expr // operand
}
A UnaryExpr node represents a unary expression. Unary "*" expressions are represented via StarExpr nodes.
func (x *UnaryExpr) End() token.Pos
func (x *UnaryExpr) Pos() token.Pos
type ValueSpec struct {
Doc *CommentGroup // associated documentation; or nil
Names []*Ident // value names (len(Names) > 0)
Type Expr // value type; or nil
Values []Expr // initial values; or nil
Comment *CommentGroup // line comments; or nil
}
A ValueSpec node represents a constant or variable declaration (ConstSpec or VarSpec production).
func (s *ValueSpec) End() token.Pos
func (s *ValueSpec) Pos() token.Pos
type Visitor interface {
Visit(node Node) (w Visitor)
}
A Visitor's Visit method is invoked for each node encountered by Walk. If the result visitor w is not nil, Walk visits each of the children of node with the visitor w, followed by a call of w.Visit(nil).