ast library Null safety

Defines the AST model. The AST (Abstract Syntax Tree) model describes the syntactic (as opposed to semantic) structure of Dart code. The semantic structure of the code is modeled by the element model.

An AST consists of nodes (instances of a subclass of AstNode). The nodes are organized in a tree structure in which the children of a node are the smaller syntactic units from which the node is composed. For example, a binary expression consists of two sub-expressions (the operands) and an operator. The two expressions are represented as nodes. The operator is not represented as a node.

The AST is constructed by the parser based on the sequence of tokens produced by the scanner. Most nodes provide direct access to the tokens used to build the node. For example, the token for the operator in a binary expression can be accessed from the node representing the binary expression.

While any node can theoretically be the root of an AST structure, almost all of the AST structures known to the analyzer have a CompilationUnit as the root of the structure. A compilation unit represents all of the Dart code in a single file.

An AST can be either unresolved or resolved. When an AST is unresolved certain properties will not have been computed and the accessors for those properties will return null. The documentation for those getters should describe that this is a possibility.

When an AST is resolved, the identifiers in the AST will be associated with the elements that they refer to and every expression in the AST will have a type associated with it.

Classes

AdjacentStrings
Two or more string literals that are implicitly concatenated because of being adjacent (separated only by whitespace).
AnnotatedNode
An AST node that can be annotated with both a documentation comment and a list of annotations.
Annotation
An annotation that can be associated with an AST node.
ArgumentList
A list of arguments in the invocation of an executable element (that is, a function, method, or constructor).
AsExpression
An as expression.
AssertInitializer
An assert in the initializer list of a constructor.
Assertion
An assertion, either in a block or in the initializer list of a constructor.
AssertStatement
An assert statement.
AssignmentExpression
An assignment expression.
AstNode
A node in the AST structure for a Dart program.
AstVisitor<R>
An object that can be used to visit an AST structure.
AugmentationImportDirective
An augmentation import directive.
AwaitExpression
An await expression.
BinaryExpression
A binary (infix) expression.
BinaryPattern
A binary (infix) pattern.
Block
A sequence of statements.
BlockFunctionBody
A function body that consists of a block of statements.
BooleanLiteral
A boolean literal expression.
BreakStatement
A break statement.
CascadeExpression
A sequence of cascaded expressions: expressions that share a common target.
CaseClause
The case clause that can optionally appear in an if statement.
CastPattern
A cast pattern.
CatchClause
A catch clause within a try statement.
CatchClauseParameter
The 'exception' or 'stackTrace' parameter in CatchClause.
ClassAugmentationDeclaration
The declaration of a class augmentation.
ClassDeclaration
The declaration of a class.
ClassMember
A node that declares a name within the scope of a class declarations.
ClassOrAugmentationDeclaration
Shared interface between ClassDeclaration and ClassAugmentationDeclaration.
ClassTypeAlias
A class type alias.
CollectionElement
An element in a list, map or set literal.
Combinator
A combinator associated with an import or export directive.
Comment
A comment within the source code.
CommentReferableExpression
An interface for an Expression which can make up a CommentReference.
CommentReference
A reference to a Dart element that is found within a documentation comment.
CompilationUnit
A compilation unit.
CompilationUnitMember
A node that declares one or more names within the scope of a compilation unit.
CompoundAssignmentExpression
A potentially compound assignment.
ConditionalExpression
A conditional expression.
Configuration
A configuration in either an import or export directive.
ConstantPattern
A constant expression being used as a pattern.
ConstructorDeclaration
A constructor declaration.
ConstructorFieldInitializer
The initialization of a field within a constructor's initialization list.
ConstructorInitializer
A node that can occur in the initializer list of a constructor declaration.
ConstructorName
The name of a constructor.
ConstructorReference
An expression representing a reference to a constructor, e.g. the expression List.filled in var x = List.filled;.
ConstructorReferenceNode
An AST node that makes reference to a constructor.
ConstructorSelector
The name of a constructor being invoked.
ContinueStatement
A continue statement.
DartPattern
A pattern.
Declaration
A node that represents the declaration of one or more names.
DeclaredIdentifier
The declaration of a single identifier.
DefaultFormalParameter
A formal parameter with a default value.
Directive
A node that represents a directive.
DoStatement
A do statement.
DottedName
A dotted name, used in a configuration within an import or export directive.
DoubleLiteral
A floating point literal expression.
EmptyFunctionBody
An empty function body, which can only appear in constructors or abstract methods.
EmptyStatement
An empty statement.
EnumConstantArguments
The arguments part of an enum constant.
EnumConstantDeclaration
The declaration of an enum constant.
EnumDeclaration
The declaration of an enumeration.
ExportDirective
An export directive.
Expression
A node that represents an expression.
ExpressionFunctionBody
A function body consisting of a single expression.
ExpressionStatement
An expression used as a statement.
ExtendsClause
The "extends" clause in a class declaration.
ExtensionDeclaration
The declaration of an extension of a type.
ExtensionOverride
An override to force resolution to choose a member from a specific extension.
FieldDeclaration
The declaration of one or more fields of the same type.
FieldFormalParameter
A field formal parameter.
ForEachParts
The parts of a for-each loop that control the iteration.
ForEachPartsWithDeclaration
The parts of a for-each loop that control the iteration when the loop variable is declared as part of the for loop.
ForEachPartsWithIdentifier
The parts of a for-each loop that control the iteration when the loop variable is declared outside of the for loop.
ForEachPartsWithPattern
A for-loop part with a pattern.
ForElement
The basic structure of a for element.
ForLoopParts
The parts of a for or for-each loop that control the iteration.
FormalParameter
A node representing a parameter to a function.
FormalParameterList
The formal parameter list of a method declaration, function declaration, or function type alias.
ForParts
The parts of a for loop that control the iteration.
ForPartsWithDeclarations
The parts of a for loop that control the iteration when there are one or more variable declarations as part of the for loop.
ForPartsWithExpression
The parts of a for loop that control the iteration when there are no variable declarations as part of the for loop.
ForPartsWithPattern
The parts of a for loop that control the iteration when there is a pattern declaration as part of the for loop.
ForStatement
A for or for-each statement.
FunctionBody
A node representing the body of a function or method.
FunctionDeclaration
A function declaration.
FunctionDeclarationStatement
A FunctionDeclaration used as a statement.
FunctionExpression
A function expression.
FunctionExpressionInvocation
The invocation of a function resulting from evaluating an expression.
FunctionReference
An expression representing a reference to a function, possibly with type arguments applied to it, e.g. the expression print in var x = print;.
FunctionTypeAlias
A function type alias.
FunctionTypedFormalParameter
A function-typed formal parameter.
GenericFunctionType
An anonymous function type.
GenericTypeAlias
A generic type alias.
GuardedPattern
The pattern with an optional WhenClause.
HideCombinator
A combinator that restricts the names being imported to those that are not in a given list.
Identifier
A node that represents an identifier.
IfElement
The basic structure of an if element.
IfStatement
An if statement.
ImplementsClause
The "implements" clause in an class declaration.
ImplicitCallReference
An expression representing an implicit 'call' method reference.
ImportDirective
An import directive.
IndexExpression
An index expression.
InstanceCreationExpression
An instance creation expression.
IntegerLiteral
An integer literal expression.
InterpolationElement
A node within a StringInterpolation.
InterpolationExpression
An expression embedded in a string interpolation.
InterpolationString
A non-empty substring of an interpolated string.
InvocationExpression
The invocation of a function or method; either a FunctionExpressionInvocation or a MethodInvocation.
IsExpression
An is expression.
Label
A label on either a LabeledStatement or a NamedExpression.
LabeledStatement
A statement that has a label associated with them.
LibraryAugmentationDirective
A library augmentation directive.
LibraryDirective
A library directive.
LibraryIdentifier
The identifier for a library.
ListLiteral
A list literal.
ListPattern
A list pattern.
ListPatternElement
An element of a list pattern.
Literal
A node that represents a literal expression.
MapLiteralEntry
A single key/value pair in a map literal.
MapPattern
A map pattern.
MapPatternElement
An element of a map pattern.
MapPatternEntry
An entry in a map pattern.
MethodDeclaration
A method declaration.
MethodInvocation
The invocation of either a function or a method.
MethodReferenceExpression
An expression that implicitly makes reference to a method.
MixinAugmentationDeclaration
The declaration of a mixin augmentation.
MixinDeclaration
The declaration of a mixin.
MixinOrAugmentationDeclaration
Shared interface between MixinDeclaration and MixinAugmentationDeclaration.
NamedCompilationUnitMember
A node that declares a single name within the scope of a compilation unit.
NamedExpression
An expression that has a name associated with it. They are used in method invocations when there are named parameters.
NamedType
A named type, which can optionally include type arguments.
NamespaceDirective
A node that represents a directive that impacts the namespace of a library.
NativeClause
The "native" clause in an class declaration.
NativeFunctionBody
A function body that consists of a native keyword followed by a string literal.
NodeList<E extends AstNode>
A list of AST nodes that have a common parent.
NormalFormalParameter
A formal parameter that is required (is not optional).
NullLiteral
A null literal expression.
NullShortableExpression
Abstract interface for expressions that may participate in null-shorting.
ObjectPattern
An object pattern.
OnClause
The "on" clause in a mixin declaration.
ParenthesizedExpression
A parenthesized expression.
ParenthesizedPattern
A parenthesized pattern.
PartDirective
A part directive.
PartOfDirective
A part-of directive.
PatternAssignment
A pattern assignment.
PatternVariableDeclaration
A pattern variable declaration.
PatternVariableDeclarationStatement
A pattern variable declaration statement.
PostfixExpression
A postfix unary expression.
PostfixPattern
A postfix (unary) pattern.
PrefixedIdentifier
An identifier that is prefixed or an access to an object property where the target of the property access is a simple identifier.
PrefixExpression
A prefix unary expression.
PropertyAccess
The access of a property of an object.
RecordLiteral
A record literal.
RecordPattern
A record pattern.
RecordPatternField
A field in a record pattern.
RecordPatternFieldName
A field name in a record pattern field.
RecordTypeAnnotation
A record type.
RecordTypeAnnotationField
A field in a RecordTypeAnnotation.
RecordTypeAnnotationNamedField
A named field in a RecordTypeAnnotation.
RecordTypeAnnotationNamedFields
The portion of a RecordTypeAnnotation with named fields.
RecordTypeAnnotationPositionalField
A positional field in a RecordTypeAnnotation.
RedirectingConstructorInvocation
The invocation of a constructor in the same class from within a constructor's initialization list.
RelationalPattern
A relational pattern.
RestPatternElement
A rest pattern element.
RethrowExpression
A rethrow expression.
ReturnStatement
A return statement.
ScriptTag
A script tag that can optionally occur at the beginning of a compilation unit.
SetOrMapLiteral
A set or map literal.
ShowCombinator
A combinator that restricts the names being imported to those in a given list.
SimpleFormalParameter
A simple formal parameter.
SimpleIdentifier
A simple identifier.
SimpleStringLiteral
A string literal expression that does not contain any interpolations.
SingleStringLiteral
A single string literal expression.
SpreadElement
A spread element.
Statement
A node that represents a statement.
StringInterpolation
A string interpolation literal.
StringLiteral
A string literal expression.
SuperConstructorInvocation
The invocation of a superclass' constructor from within a constructor's initialization list.
SuperExpression
A super expression.
SuperFormalParameter
A super-initializer formal parameter.
SwitchCase
A case in a switch statement.
SwitchDefault
The default case in a switch statement.
SwitchExpression
A switch expression.
SwitchExpressionCase
A case in a switch expression.
SwitchMember
An element within a switch statement.
SwitchPatternCase
A pattern-based case in a switch statement.
SwitchStatement
A switch statement.
SymbolLiteral
A symbol literal expression.
ThisExpression
A this expression.
ThrowExpression
A throw expression.
TopLevelVariableDeclaration
The declaration of one or more top-level variables of the same type.
TryStatement
A try statement.
TypeAlias
The declaration of a type alias.
TypeAnnotation
A type annotation.
TypeArgumentList
A list of type arguments.
TypedLiteral
A literal that has a type associated with it.
TypeLiteral
An expression representing a type, e.g. the expression int in var x = int;.
TypeParameter
A type parameter.
TypeParameterList
Type parameters within a declaration.
UriBasedDirective
A directive that references a URI.
VariableDeclaration
An identifier that has an initial value associated with it.
VariableDeclarationList
The declaration of one or more variables of the same type.
VariableDeclarationStatement
A list of variables that are being declared in a context where a statement is required.
VariablePattern
A variable pattern.
WhenClause
A guard in a pattern-based case in a switch statement, switch expression, if statement, or if element.
WhileStatement
A while statement.
WithClause
The with clause in a class declaration.
YieldStatement
A yield statement.