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Abstract syntax tree classes for working with Go programs

CodeQL has a large selection of classes for representing the abstract syntax tree of Go programs.

The abstract syntax tree (AST) represents the syntactic structure of a program. Nodes on the AST represent elements such as statements and expressions.

Statement classes

This table lists all subclasses of Stmt.

Statement syntax	CodeQL class	Superclasses	Remarks
;	EmptyStmt
Expr	ExprStmt
{ Stmt ... }	BlockStmt
if Expr BlockStmt	IfStmt
if Expr BlockStmt else Stmt
if Stmt; Expr BlockStmt
for Expr BlockStmt	ForStmt	LoopStmt
for Stmt; Expr; Stmt BlockStmt
for Expr ... = range Expr BlockStmt	RangeStmt	LoopStmt
switch Expr { CaseClause ... }	ExpressionSwitchStmt	SwitchStmt
switch Stmt; Expr { CaseClause ... }
switch Expr.(type) { CaseClause ... }	TypeSwitchStmt	SwitchStmt
switch SimpleAssignStmt.(type) { CaseClause ... }
switch Stmt; Expr.(type) { CaseClause ... }
select { CommClause ... }	SelectStmt
return	ReturnStmt
break	BreakStmt	BranchStmt
continue	ContinueStmt	BranchStmt
goto LabelName	GotoStmt	BranchStmt
fallthrough	FallthroughStmt	BranchStmt	can only occur as final non-empty child of a CaseClause in an ExpressionSwitchStmt
LabelName: Stmt	LabeledStmt
var VariableName TypeName	DeclStmt
const VariableName = Expr
type TypeName TypeExpr
type TypeName = TypeExpr
Expr ... = Expr ...	AssignStmt	SimpleAssignStmt, Assignment
VariableName ... := Expr ...	DefineStmt	SimpleAssignStmt, Assignment
Expr += Expr	AddAssignStmt	CompoundAssignStmt, Assignment
Expr -= Expr	SubAssignStmt	CompoundAssignStmt, Assignment
Expr *= Expr	MulAssignStmt	CompoundAssignStmt, Assignment
Expr /= Expr	QuoAssignStmt	CompoundAssignStmt, Assignment
Expr %= Expr	RemAssignStmt	CompoundAssignStmt, Assignment
Expr *= Expr	MulAssignStmt	CompoundAssignStmt, Assignment
Expr &= Expr	AndAssignStmt	CompoundAssignStmt, Assignment
Expr |= Expr	OrAssignStmt	CompoundAssignStmt, Assignment
Expr ^= Expr	XorAssignStmt	CompoundAssignStmt, Assignment
Expr <<= Expr	ShlAssignStmt	CompoundAssignStmt, Assignment
Expr >>= Expr	ShrAssignStmt	CompoundAssignStmt, Assignment
Expr &^= Expr	AndNotAssignStmt	CompoundAssignStmt, Assignment
Expr ++	IncStmt	IncDecStmt
Expr --	DecStmt	IncDecStmt
go CallExpr	GoStmt
defer CallExpr	DeferStmt
Expr <- Expr	SendStmt
case Expr ...: Stmt ...	CaseClause		can only occur as child of a SwitchStmt
case TypeExpr ...: Stmt ...
default: Stmt ...
case SendStmt: Stmt ...	CommClause		can only occur as child of a SelectStmt
case RecvStmt: Stmt ...
default: Stmt ...
Expr ... = RecvExpr	RecvStmt		can only occur as child of a CommClause
VariableName ... := RecvExpr
(anything unparseable)	BadStmt

Expression classes

There are many expression classes, so we present them by category. All classes in this section are subclasses of Expr.

Literals

Expression syntax example	CodeQL class	Superclass
23	IntLit	BasicLit
4.2	FloatLit	BasicLit
4.2 + 2.7i	ImagLit	BasicLit
'a'	CharLit	BasicLit
"Hello"	StringLit	BasicLit
func(x, y int) int { return x + y }	FuncLit	FuncDef
map[string]int{"A": 1, "B": 2}	MapLit	CompositeLit
Point3D{0.5, -0.5, 0.5}	StructLit	CompositeLit

Unary expressions

All classes in this subsection are subclasses of UnaryExpr.

Expression syntax	CodeQL class	Superclasses
+Expr	PlusExpr	ArithmeticUnaryExpr
-Expr	MinusExpr	ArithmeticUnaryExpr
!Expr	NotExpr	LogicalUnaryExpr
^Expr	ComplementExpr	BitwiseUnaryExpr
&Expr	AddressExpr
<-Expr	RecvExpr

Binary expressions

All classes in this subsection are subclasses of BinaryExpr.

Expression syntax	CodeQL class	Superclasses
Expr * Expr	MulExpr	ArithmeticBinaryExpr
Expr / Expr	QuoExpr	ArithmeticBinaryExpr
Expr % Expr	RemExpr	ArithmeticBinaryExpr
Expr + Expr	AddExpr	ArithmeticBinaryExpr
Expr - Expr	SubExpr	ArithmeticBinaryExpr
Expr << Expr	ShlExpr	ShiftExpr
Expr >> Expr	ShrExpr	ShiftExpr
Expr && Expr	LandExpr	LogicalBinaryExpr
Expr || Expr	LorExpr	LogicalBinaryExpr
Expr < Expr	LssExpr	RelationalComparisonExpr
Expr > Expr	GtrExpr	RelationalComparisonExpr
Expr <= Expr	LeqExpr	RelationalComparisonExpr
Expr >= Expr	GeqExpr	RelationalComparisonExpr
Expr == Expr	EqlExpr	EqualityTestExpr
Expr != Expr	NeqExpr	EqualityTestExpr
Expr & Expr	AndExpr	BitwiseBinaryExpr
Expr | Expr	OrExpr	BitwiseBinaryExpr
Expr ^ Expr	XorExpr	BitwiseBinaryExpr
Expr &^ Expr	AndNotExpr	BitwiseBinaryExpr

Type expressions

These classes represent different expressions for types. They do not have a common superclass.

Expression syntax	CodeQL class	Superclasses
[Expr] TypeExpr	ArrayTypeExpr
struct { ... }	StructTypeExpr
func FunctionName(...) (...)	FuncTypeExpr
interface { ... }	InterfaceTypeExpr
map[TypeExpr]TypeExpr	MapTypeExpr
chan<- TypeExpr	SendChanTypeExpr	ChanTypeExpr
<-chan TypeExpr	RecvChanTypeExpr	ChanTypeExpr
chan TypeExpr	SendRecvChanTypeExpr	ChanTypeExpr

Name expressions

All classes in this subsection are subclasses of Name.

The following classes relate to the structure of the name.

Expression syntax	CodeQL class	Superclasses
Ident	SimpleName	Ident
Ident.Ident	QualifiedName	SelectorExpr

The following classes relate to what sort of entity the name refers to.

• PackageName

• TypeName

• LabelName

• ValueName

  • ConstantName

  • VariableName

  • FunctionName

Miscellaneous

Expression syntax	CodeQL class	Superclasses	Remarks
foo	Ident
_	BlankIdent
...	Ellipsis
(Expr)	ParenExpr
Ident.Ident	SelectorExpr
Expr[Expr]	IndexExpr
Expr[Expr:Expr:Expr]	SliceExpr
Expr.(TypeExpr)	TypeAssertExpr
*Expr	StarExpr		can be a ValueExpr or TypeExpr depending on context
Expr: Expr	KeyValueExpr
TypeExpr(Expr)	ConversionExpr	CallOrConversionExpr
Expr(...)	CallExpr	CallOrConversionExpr
(anything unparseable)	BadExpr

The following classes organize expressions by the kind of entity they refer to.

CodeQL class	Explanation
TypeExpr	an expression that denotes a type
ReferenceExpr	an expression that refers to a variable, a constant, a function, a field, or an element of an array or a slice
ValueExpr	an expression that can be evaluated to a value (as opposed to expressions that refer to a package, a type, or a statement label). This generalizes ReferenceExpr

Further reading

• CodeQL queries for Go

• Example queries for Go

• CodeQL library reference for Go

• “QL language reference”

• “CodeQL tools”

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