How to use tryConsume method of ast Package

Best Syzkaller code snippet using ast.tryConsume

parser_impl.go

Source:parser_impl.go

...147	p.currentNode().Connect(dslshape.NodePredicateChild, errorNode)148}149// consumeKeyword consumes an expected keyword token or adds an error node.150func (p *sourceParser) consumeKeyword(keyword string) bool {151	if !p.tryConsumeKeyword(keyword) {152		p.emitErrorf("Expected keyword %s, found token %v", keyword, p.currentToken.Kind)153		return false154	}155	return true156}157// tryConsumeKeyword attempts to consume an expected keyword token.158func (p *sourceParser) tryConsumeKeyword(keyword string) bool {159	if !p.isKeyword(keyword) {160		return false161	}162	p.consumeToken()163	return true164}165// cosumeIdentifier consumes an expected identifier token or adds an error node.166func (p *sourceParser) consumeIdentifier() (string, bool) {167	token, ok := p.tryConsume(lexer.TokenTypeIdentifier)168	if !ok {169		p.emitErrorf("Expected identifier, found token %v", p.currentToken.Kind)170		return "", false171	}172	return token.Value, true173}174// consume performs consumption of the next token if it matches any of the given175// types and returns it. If no matching type is found, adds an error node.176func (p *sourceParser) consume(types ...lexer.TokenType) (lexer.Lexeme, bool) {177	token, ok := p.tryConsume(types...)178	if !ok {179		p.emitErrorf("Expected one of: %v, found: %v", types, p.currentToken.Kind)180	}181	return token, ok182}183// tryConsume performs consumption of the next token if it matches any of the given184// types and returns it.185func (p *sourceParser) tryConsume(types ...lexer.TokenType) (lexer.Lexeme, bool) {186	token, found := p.tryConsumeWithComments(types...)187	return token.Lexeme, found188}189// tryConsume performs consumption of the next token if it matches any of the given190// types and returns it.191func (p *sourceParser) tryConsumeWithComments(types ...lexer.TokenType) (commentedLexeme, bool) {192	if p.isToken(types...) {193		token := p.currentToken194		p.consumeToken()195		return token, true196	}197	return commentedLexeme{lexer.Lexeme{198		Kind: lexer.TokenTypeError,199	}, make([]string, 0)}, false200}201// performLeftRecursiveParsing performs left-recursive parsing of a set of operators. This method202// first performs the parsing via the subTryExprFn and then checks for one of the left-recursive203// operator token types found. If none found, the left expression is returned. Otherwise, the204// rightNodeBuilder is called to attempt to construct an operator expression. This method also205// properly handles decoration of the nodes with their proper start and end run locations and206// comments.207func (p *sourceParser) performLeftRecursiveParsing(subTryExprFn tryParserFn, rightNodeBuilder rightNodeConstructor, rightTokenTester lookaheadParserFn, operatorTokens ...lexer.TokenType) (AstNode, bool) {208	var currentLeftToken commentedLexeme209	currentLeftToken = p.currentToken210	// Consume the left side of the expression.211	leftNode, ok := subTryExprFn()212	if !ok {213		return nil, false214	}215	// Check for an operator token. If none found, then we've found just the left side of the216	// expression and so we return that node.217	if !p.isToken(operatorTokens...) {218		return leftNode, true219	}220	// Keep consuming pairs of operators and child expressions until such221	// time as no more can be consumed. We use this loop+custom build rather than recursion222	// because these operators are *left* recursive, not right.223	var currentLeftNode AstNode224	currentLeftNode = leftNode225	for {226		// Check for an operator.227		if !p.isToken(operatorTokens...) {228			break229		}230		// If a lookahead function is defined, check the lookahead for the matched token.231		if rightTokenTester != nil && !rightTokenTester(p.currentToken.Lexeme) {232			break233		}234		// Consume the operator.235		operatorToken, ok := p.tryConsumeWithComments(operatorTokens...)236		if !ok {237			break238		}239		// Consume the right hand expression and build an expression node (if applicable).240		exprNode, ok := rightNodeBuilder(currentLeftNode, operatorToken.Lexeme)241		if !ok {242			p.emitErrorf("Expected right hand expression, found: %v", p.currentToken.Kind)243			return currentLeftNode, true244		}245		p.decorateStartRuneAndComments(exprNode, currentLeftToken)246		p.decorateEndRune(exprNode, p.previousToken)247		currentLeftNode = exprNode248		currentLeftToken = operatorToken249	}250	return currentLeftNode, true251}252// tryConsumeStatementTerminator tries to consume a statement terminator.253func (p *sourceParser) tryConsumeStatementTerminator() (lexer.Lexeme, bool) {254	return p.tryConsume(lexer.TokenTypeSyntheticSemicolon, lexer.TokenTypeSemicolon, lexer.TokenTypeEOF)255}256// consumeStatementTerminator consume a statement terminator.257func (p *sourceParser) consumeStatementTerminator() bool {258	_, ok := p.tryConsumeStatementTerminator()259	if ok {260		return true261	}262	p.emitErrorf("Expected end of statement or definition, found: %s", p.currentToken.Kind)263	return false264}265// binaryOpDefinition represents information a binary operator token and its associated node type.266type binaryOpDefinition struct {267	// The token representing the binary expression's operator.268	BinaryOperatorToken lexer.TokenType269	// The type of node to create for this expression.270	BinaryExpressionNodeType dslshape.NodeType271}272// buildBinaryOperatorExpressionFnTree builds a tree of functions to try to consume a set of binary273// operator expressions.274func (p *sourceParser) buildBinaryOperatorExpressionFnTree(ops []binaryOpDefinition) tryParserFn {275	// Start with a base expression function.276	var currentParseFn tryParserFn277	currentParseFn = func() (AstNode, bool) {278		arrowExpr, ok := p.tryConsumeArrowExpression()279		if !ok {280			return p.tryConsumeBaseExpression()281		}282		return arrowExpr, true283	}284	for i := range ops {285		// Note: We have to reverse this to ensure we have proper precedence.286		currentParseFn = func(operatorInfo binaryOpDefinition, currentFn tryParserFn) tryParserFn {287			return (func() (AstNode, bool) {288				return p.tryConsumeComputeExpression(currentFn, operatorInfo.BinaryOperatorToken, operatorInfo.BinaryExpressionNodeType)289			})290		}(ops[len(ops)-i-1], currentParseFn)291	}292	return currentParseFn293}...

parser.go

Source:parser.go

...35		if p.isToken(lexer.TokenTypeEOF) {36			break Loop37		}38		// Consume a statement terminator if one was found.39		p.tryConsumeStatementTerminator()40		if p.isToken(lexer.TokenTypeEOF) {41			break Loop42		}43		// The top level of the DSL is a set of definitions:44		// definition foobar { ... }45		switch {46		case p.isKeyword("definition"):47			rootNode.Connect(dslshape.NodePredicateChild, p.consumeDefinition())48		default:49			p.emitErrorf("Unexpected token at root level: %v", p.currentToken.Kind)50			break Loop51		}52	}53	return rootNode54}55// consumeDefinition attempts to consume a single schema definition.56// ```definition somedef { ... }````57func (p *sourceParser) consumeDefinition() AstNode {58	defNode := p.startNode(dslshape.NodeTypeDefinition)59	defer p.finishNode()60	// definition ...61	p.consumeKeyword("definition")62	definitionName, ok := p.consumeTypePath()63	if !ok {64		return defNode65	}66	defNode.Decorate(dslshape.NodeDefinitionPredicateName, definitionName)67	// {68	_, ok = p.consume(lexer.TokenTypeLeftBrace)69	if !ok {70		return defNode71	}72	// Relations and permissions.73	for {74		// }75		if _, ok := p.tryConsume(lexer.TokenTypeRightBrace); ok {76			break77		}78		// relation ...79		// permission ...80		switch {81		case p.isKeyword("relation"):82			defNode.Connect(dslshape.NodePredicateChild, p.consumeRelation())83		case p.isKeyword("permission"):84			defNode.Connect(dslshape.NodePredicateChild, p.consumePermission())85		}86		ok := p.consumeStatementTerminator()87		if !ok {88			break89		}90	}91	return defNode92}93// consumeRelation consumes a relation.94// ```relation foo: sometype```95func (p *sourceParser) consumeRelation() AstNode {96	relNode := p.startNode(dslshape.NodeTypeRelation)97	defer p.finishNode()98	// relation ...99	p.consumeKeyword("relation")100	relationName, ok := p.consumeIdentifier()101	if !ok {102		return relNode103	}104	relNode.Decorate(dslshape.NodePredicateName, relationName)105	// :106	_, ok = p.consume(lexer.TokenTypeColon)107	if !ok {108		return relNode109	}110	// Relation allowed type(s).111	relNode.Connect(dslshape.NodeRelationPredicateAllowedTypes, p.consumeTypeReference())112	return relNode113}114// consumeTypeReference consumes a reference to a type or types of relations.115// ```sometype | anothertype | anothertype:* ```116func (p *sourceParser) consumeTypeReference() AstNode {117	refNode := p.startNode(dslshape.NodeTypeTypeReference)118	defer p.finishNode()119	for {120		refNode.Connect(dslshape.NodeTypeReferencePredicateType, p.consumeSpecificType())121		if _, ok := p.tryConsume(lexer.TokenTypePipe); !ok {122			break123		}124	}125	return refNode126}127// consumeSpecificType consumes an identifier as a specific type reference.128func (p *sourceParser) consumeSpecificType() AstNode {129	specificNode := p.startNode(dslshape.NodeTypeSpecificTypeReference)130	defer p.finishNode()131	typeName, ok := p.consumeTypePath()132	if !ok {133		return specificNode134	}135	specificNode.Decorate(dslshape.NodeSpecificReferencePredicateType, typeName)136	// Check for a wildcard137	if _, ok := p.tryConsume(lexer.TokenTypeColon); ok {138		_, ok := p.consume(lexer.TokenTypeStar)139		if !ok {140			return specificNode141		}142		specificNode.Decorate(dslshape.NodeSpecificReferencePredicateWildcard, "true")143		return specificNode144	}145	// Check for a relation specified.146	if _, ok := p.tryConsume(lexer.TokenTypeHash); !ok {147		return specificNode148	}149	// Consume an identifier or an ellipsis.150	consumed, ok := p.consume(lexer.TokenTypeIdentifier, lexer.TokenTypeEllipsis)151	if !ok {152		return specificNode153	}154	specificNode.Decorate(dslshape.NodeSpecificReferencePredicateRelation, consumed.Value)155	return specificNode156}157func (p *sourceParser) consumeTypePath() (string, bool) {158	typeNameOrNamespace, ok := p.consumeIdentifier()159	if !ok {160		return "", false161	}162	_, ok = p.tryConsume(lexer.TokenTypeDiv)163	if !ok {164		return typeNameOrNamespace, true165	}166	typeName, ok := p.consumeIdentifier()167	if !ok {168		return "", false169	}170	return fmt.Sprintf("%s/%s", typeNameOrNamespace, typeName), true171}172// consumePermission consumes a permission.173// ```permission foo = bar + baz```174func (p *sourceParser) consumePermission() AstNode {175	permNode := p.startNode(dslshape.NodeTypePermission)176	defer p.finishNode()177	// permission ...178	p.consumeKeyword("permission")179	permissionName, ok := p.consumeIdentifier()180	if !ok {181		return permNode182	}183	permNode.Decorate(dslshape.NodePredicateName, permissionName)184	// =185	_, ok = p.consume(lexer.TokenTypeEquals)186	if !ok {187		return permNode188	}189	permNode.Connect(dslshape.NodePermissionPredicateComputeExpression, p.consumeComputeExpression())190	return permNode191}192// ComputeExpressionOperators defines the binary operators in precedence order.193var ComputeExpressionOperators = []binaryOpDefinition{194	{lexer.TokenTypeMinus, dslshape.NodeTypeExclusionExpression},195	{lexer.TokenTypeAnd, dslshape.NodeTypeIntersectExpression},196	{lexer.TokenTypePlus, dslshape.NodeTypeUnionExpression},197}198// consumeComputeExpression consumes an expression for computing a permission.199func (p *sourceParser) consumeComputeExpression() AstNode {200	// Compute expressions consist of a set of binary operators, so build a tree with proper201	// precedence.202	binaryParser := p.buildBinaryOperatorExpressionFnTree(ComputeExpressionOperators)203	found, ok := binaryParser()204	if !ok {205		return p.createErrorNodef("Expected compute expression for permission")206	}207	return found208}209// tryConsumeComputeExpression attempts to consume a nested compute expression.210func (p *sourceParser) tryConsumeComputeExpression(subTryExprFn tryParserFn, binaryTokenType lexer.TokenType, nodeType dslshape.NodeType) (AstNode, bool) {211	rightNodeBuilder := func(leftNode AstNode, operatorToken lexer.Lexeme) (AstNode, bool) {212		rightNode, ok := subTryExprFn()213		if !ok {214			return nil, false215		}216		// Create the expression node representing the binary expression.217		exprNode := p.createNode(nodeType)218		exprNode.Connect(dslshape.NodeExpressionPredicateLeftExpr, leftNode)219		exprNode.Connect(dslshape.NodeExpressionPredicateRightExpr, rightNode)220		return exprNode, true221	}222	return p.performLeftRecursiveParsing(subTryExprFn, rightNodeBuilder, nil, binaryTokenType)223}224// tryConsumeArrowExpression attempts to consume an arrow expression.225// ```foo->bar->baz->meh```226func (p *sourceParser) tryConsumeArrowExpression() (AstNode, bool) {227	rightNodeBuilder := func(leftNode AstNode, operatorToken lexer.Lexeme) (AstNode, bool) {228		rightNode, ok := p.tryConsumeBaseExpression()229		if !ok {230			return nil, false231		}232		// Create the expression node representing the binary expression.233		exprNode := p.createNode(dslshape.NodeTypeArrowExpression)234		exprNode.Connect(dslshape.NodeExpressionPredicateLeftExpr, leftNode)235		exprNode.Connect(dslshape.NodeExpressionPredicateRightExpr, rightNode)236		return exprNode, true237	}238	return p.performLeftRecursiveParsing(p.tryConsumeIdentifierLiteral, rightNodeBuilder, nil, lexer.TokenTypeRightArrow)239}240// tryConsumeBaseExpression attempts to consume base compute expressions (identifiers, parenthesis).241// ```(foo + bar)```242// ```(foo)```243// ```foo```244// ```nil```245func (p *sourceParser) tryConsumeBaseExpression() (AstNode, bool) {246	switch {247	// Nested expression.248	case p.isToken(lexer.TokenTypeLeftParen):249		comments := p.currentToken.comments250		p.consume(lexer.TokenTypeLeftParen)251		exprNode := p.consumeComputeExpression()252		p.consume(lexer.TokenTypeRightParen)253		// Attach any comments found to the consumed expression.254		p.decorateComments(exprNode, comments)255		return exprNode, true256	// Nil expression.257	case p.isKeyword("nil"):258		return p.tryConsumeNilExpression()259	// Identifier.260	case p.isToken(lexer.TokenTypeIdentifier):261		return p.tryConsumeIdentifierLiteral()262	}263	return nil, false264}265// tryConsumeIdentifierLiteral attempts to consume an identifier as a literal266// expression.267//268// ```foo```269func (p *sourceParser) tryConsumeIdentifierLiteral() (AstNode, bool) {270	if !p.isToken(lexer.TokenTypeIdentifier) {271		return nil, false272	}273	identNode := p.startNode(dslshape.NodeTypeIdentifier)274	defer p.finishNode()275	identifier, _ := p.consumeIdentifier()276	identNode.Decorate(dslshape.NodeIdentiferPredicateValue, identifier)277	return identNode, true278}279func (p *sourceParser) tryConsumeNilExpression() (AstNode, bool) {280	if !p.isKeyword("nil") {281		return nil, false282	}283	node := p.startNode(dslshape.NodeTypeNilExpression)284	p.consumeKeyword("nil")285	defer p.finishNode()286	return node, true287}...

parser_rules.go

Source:parser_rules.go

...63func (p *sourceParser) consumeDeclaration() AstNode {64	declNode := p.startNode(NodeTypeDeclaration)65	defer p.finishNode()66	// Consume any annotations.67	p.tryConsumeAnnotations(declNode, NodePredicateDeclarationAnnotation)68	// Consume the type of declaration.69	if !p.consumeKeyword("interface") {70		return declNode71	}72	declNode.Decorate(NodePredicateDeclarationKind, "interface")73	// Consume the name of the declaration.74	declNode.Decorate(NodePredicateDeclarationName, p.consumeIdentifier())75	// Check for (optional) inheritance.76	if _, ok := p.tryConsume(tokenTypeColon); ok {77		declNode.Decorate(NodePredicateDeclarationParentType, p.consumeIdentifier())78	}79	// {80	p.consume(tokenTypeLeftBrace)81	// Members and custom operations (if any).82loop:83	for {84		if p.isToken(tokenTypeRightBrace) {85			break86		}87		if p.isKeyword("serializer") || p.isKeyword("jsonifier") {88			customOpNode := p.startNode(NodeTypeCustomOp)89			customOpNode.Decorate(NodePredicateCustomOpName, p.currentToken.value)90			p.consume(tokenTypeKeyword)91			_, ok := p.consume(tokenTypeSemicolon)92			p.finishNode()93			declNode.Connect(NodePredicateDeclarationCustomOperation, customOpNode)94			if !ok {95				break loop96			}97			continue98		}99		declNode.Connect(NodePredicateDeclarationMember, p.consumeMember())100		if _, ok := p.consume(tokenTypeSemicolon); !ok {101			break102		}103	}104	// };105	p.consume(tokenTypeRightBrace)106	p.consume(tokenTypeSemicolon)107	return declNode108}109// consumeMember attempts to consume a member definition in a declaration.110func (p *sourceParser) consumeMember() AstNode {111	memberNode := p.startNode(NodeTypeMember)112	defer p.finishNode()113	var isAttribute = false114	// annotations115	p.tryConsumeAnnotations(memberNode, NodePredicateMemberAnnotation)116	// getter/setter117	var specialization = ""118	if p.isKeyword("getter") || p.isKeyword("setter") {119		consumed, _ := p.consume(tokenTypeKeyword)120		specialization = consumed.value121		memberNode.Decorate(NodePredicateMemberSpecialization, specialization)122	}123	// static readonly attribute124	if p.tryConsumeKeyword("static") {125		memberNode.Decorate(NodePredicateMemberStatic, "true")126	}127	if p.tryConsumeKeyword("readonly") {128		memberNode.Decorate(NodePredicateMemberReadonly, "true")129	}130	if p.tryConsumeKeyword("attribute") {131		isAttribute = true132		memberNode.Decorate(NodePredicateMemberAttribute, "true")133	}134	// Consume the type of the member.135	memberNode.Decorate(NodePredicateMemberType, p.consumeType())136	// Consume the member's name.137	if specialization == "" {138		memberNode.Decorate(NodePredicateMemberName, p.consumeIdentifier())139	}140	// If not an attribute, consume the parameters of the member.141	if !isAttribute {142		p.consumeParameters(memberNode, NodePredicateMemberParameter)143	}144	return memberNode145}146// tryConsumeAnnotations consumes any annotations found on the parent node.147func (p *sourceParser) tryConsumeAnnotations(parentNode AstNode, predicate string) {148	for {149		// [150		if _, ok := p.tryConsume(tokenTypeLeftBracket); !ok {151			return152		}153		for {154			// Foo()155			parentNode.Connect(predicate, p.consumeAnnotationPart())156			// ,157			if _, ok := p.tryConsume(tokenTypeComma); !ok {158				break159			}160		}161		// ]162		if _, ok := p.consume(tokenTypeRightBracket); !ok {163			return164		}165	}166}167// consumeAnnotationPart consumes an annotation, as found within a set of brackets `[]`.168func (p *sourceParser) consumeAnnotationPart() AstNode {169	annotationNode := p.startNode(NodeTypeAnnotation)170	defer p.finishNode()171	// Consume the name of the annotation.172	annotationNode.Decorate(NodePredicateAnnotationName, p.consumeIdentifier())173	// Consume (optional) value.174	if _, ok := p.tryConsume(tokenTypeEquals); ok {175		annotationNode.Decorate(NodePredicateAnnotationDefinedValue, p.consumeIdentifier())176	}177	// Consume (optional) parameters.178	if p.isToken(tokenTypeLeftParen) {179		p.consumeParameters(annotationNode, NodePredicateAnnotationParameter)180	}181	return annotationNode182}183// expandedTypeKeywords defines the keywords that form the prefixes for expanded types:184// two-identifier type names.185var expandedTypeKeywords = map[string][]string{186	"unsigned":     []string{"short", "long"},187	"long":         []string{"long"},188	"unrestricted": []string{"float", "double"},189}190// consumeType attempts to consume a type (identifier (with optional ?) or 'any').191func (p *sourceParser) consumeType() string {192	if p.tryConsumeKeyword("any") {193		return "any"194	}195	var typeName = ""196	identifier := p.consumeIdentifier()197	typeName += identifier198	// If the identifier is the beginning of a possible expanded type name, check for the199	// secondary portion.200	if secondaries, ok := expandedTypeKeywords[identifier]; ok {201		for _, secondary := range secondaries {202			if p.isToken(tokenTypeIdentifier) && p.currentToken.value == secondary {203				typeName += " " + secondary204				p.consume(tokenTypeIdentifier)205				break206			}207		}208	}209	if _, ok := p.tryConsume(tokenTypeQuestionMark); ok {210		return typeName + "?"211	} else {212		return typeName213	}214}215// consumeParameter attempts to consume a parameter.216func (p *sourceParser) consumeParameter() AstNode {217	paramNode := p.startNode(NodeTypeParameter)218	defer p.finishNode()219	// optional220	if p.tryConsumeKeyword("optional") {221		paramNode.Decorate(NodePredicateParameterOptional, "true")222	}223	// Consume the parameter's type.224	paramNode.Decorate(NodePredicateParameterType, p.consumeType())225	// Consume the parameter's name.226	paramNode.Decorate(NodePredicateParameterName, p.consumeIdentifier())227	return paramNode228}229// consumeParameters attempts to consume a set of parameters.230func (p *sourceParser) consumeParameters(parentNode AstNode, predicate string) {231	p.consume(tokenTypeLeftParen)232	if _, ok := p.tryConsume(tokenTypeRightParen); ok {233		return234	}235	for {236		parentNode.Connect(predicate, p.consumeParameter())237		if _, ok := p.tryConsume(tokenTypeRightParen); ok {238			return239		}240		if _, ok := p.consume(tokenTypeComma); !ok {241			return242		}243	}244}245// consumeImplementation attempts to consume an implementation definition.246func (p *sourceParser) consumeImplementation() AstNode {247	implNode := p.startNode(NodeTypeImplementation)248	defer p.finishNode()249	// identifier250	implNode.Decorate(NodePredicateImplementationName, p.consumeIdentifier())251	// implements...

tryConsume

Using AI Code Generation

1import (2func main() {3    f, err := parser.ParseFile(fset, "2.go", nil, parser.ImportsOnly)4    if err != nil {5        fmt.Println(err)6    }7    for _, s := range f.Imports {8        fmt.Println(s.Path.Value)9    }10}11import (12func main() {13    f, err := parser.ParseFile(fset, "3.go", nil, 0)14    if err != nil {15        fmt.Println(err)16    }17    ast.Print(fset, f)18}

tryConsume

Using AI Code Generation

1import (2func main() {3func main() {4}5    fset := token.NewFileSet()6    f, err := parser.ParseFile(fset, "src.go", src, parser.ParseComments)7    if err != nil {8        log.Fatal(err)9    }10    ast.Inspect(f, func(n ast.Node) bool {11        if x, ok := n.(*ast.AssignStmt); ok {12            if len(x.Lhs) == 1 && len(x.Rhs) == 1 {13                if ident, ok := x.Lhs[0].(*ast.Ident); ok {14                    if ident.Obj == nil || ident.Obj.Kind != ast.Var {15                    }16                }17            }18            fmt.Printf("%s19", fset.Position(x.TokPos))20        }21    })22}23import (24func main() {25func main() {26}27    fset := token.NewFileSet()28    f, err := parser.ParseFile(fset, "src.go", src, parser.ParseComments)29    if err != nil {30        log.Fatal(err)31    }32    ast.Inspect(f, func(n ast.Node) bool {33        if x, ok := n.(*ast.AssignStmt); ok {34            if len(x.Lhs) == 1 && len(x.Rhs) == 1 {35                if ident, ok := x.Lhs[0].(*ast.Ident); ok {36                    if ident.Obj == nil || ident.Obj.Kind != ast.Var {37                    }38                }39            }40            fmt.Printf("%s41", fset.Position(x.TokPos))42        }43    })44}

tryConsume

Using AI Code Generation

1func main() {2    a := ast.New(s)3    a.TryConsume("a")4    a.TryConsume("b")5    a.TryConsume("c")6    a.TryConsume("d")7    fmt.Println(a)8}9func main() {10    a := ast.New(s)11    a.TryConsume("a")12    a.TryConsume("b")13    a.TryConsume("c")14    a.TryConsume("d")15    fmt.Println(a)16}17func main() {18    a := ast.New(s)19    a.TryConsume("a")20    a.TryConsume("b")21    a.TryConsume("c")22    a.TryConsume("d")23    fmt.Println(a)24}25func main() {26    a := ast.New(s)27    a.TryConsume("a")28    a.TryConsume("b")29    a.TryConsume("c")30    a.TryConsume("d")31    fmt.Println(a)32}33func main() {34    a := ast.New(s)35    a.TryConsume("a")36    a.TryConsume("b")37    a.TryConsume("c")38    a.TryConsume("d")39    fmt.Println(a)40}41func main() {42    a := ast.New(s)43    a.TryConsume("a")44    a.TryConsume("b")45    a.TryConsume("c")46    a.TryConsume("d")47    fmt.Println(a)48}49func main() {50    a := ast.New(s)

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