Signature help implementation (#861)

Author: navya9singh

internal/ast/utilities.go

@@ -1948,7 +1948,10 @@ func IsComputedNonLiteralName(name *Node) bool {
 }
 
 func IsQuestionToken(node *Node) bool {
-	return node != nil && node.Kind == KindQuestionToken
+	if node == nil {
+		return false
+	}
+	return node.Kind == KindQuestionToken
 }
 
 func GetTextOfPropertyName(name *Node) string {
@@ -3385,3 +3388,75 @@ func IsRightSideOfQualifiedNameOrPropertyAccess(node *Node) bool {
 	}
 	return false
 }
+
+func HasQuestionToken(node *Node) bool {
+	switch node.Kind {
+	case KindParameter:
+		return node.AsParameterDeclaration().QuestionToken != nil
+	case KindMethodDeclaration:
+		return IsQuestionToken(node.AsMethodDeclaration().PostfixToken)
+	case KindShorthandPropertyAssignment:
+		return IsQuestionToken(node.AsShorthandPropertyAssignment().PostfixToken)
+	case KindMethodSignature:
+		return IsQuestionToken(node.AsMethodSignatureDeclaration().PostfixToken)
+	case KindPropertySignature:
+		return IsQuestionToken(node.AsPropertySignatureDeclaration().PostfixToken)
+	case KindPropertyAssignment:
+		return IsQuestionToken(node.AsPropertyAssignment().PostfixToken)
+	case KindPropertyDeclaration:
+		return IsQuestionToken(node.AsPropertyDeclaration().PostfixToken)
+	}
+	return false
+}
+
+func IsJsxOpeningLikeElement(node *Node) bool {
+	return IsJsxOpeningElement(node) || IsJsxSelfClosingElement(node)
+}
+
+func GetInvokedExpression(node *Node) *Node {
+	switch node.Kind {
+	case KindTaggedTemplateExpression:
+		return node.AsTaggedTemplateExpression().Tag
+	case KindJsxOpeningElement, KindJsxSelfClosingElement:
+		return node.TagName()
+	case KindBinaryExpression:
+		return node.AsBinaryExpression().Right
+	default:
+		return node.Expression()
+	}
+}
+
+func IsCallOrNewExpression(node *Node) bool {
+	return IsCallExpression(node) || IsNewExpression(node)
+}
+
+func CanHaveSymbol(node *Node) bool {
+	switch node.Kind {
+	case KindArrowFunction, KindBinaryExpression, KindBindingElement, KindCallExpression, KindCallSignature,
+		KindClassDeclaration, KindClassExpression, KindClassStaticBlockDeclaration, KindConstructor, KindConstructorType,
+		KindConstructSignature, KindElementAccessExpression, KindEnumDeclaration, KindEnumMember, KindExportAssignment, KindJSExportAssignment,
+		KindExportDeclaration, KindExportSpecifier, KindFunctionDeclaration, KindFunctionExpression, KindFunctionType,
+		KindGetAccessor, KindIdentifier, KindImportClause, KindImportEqualsDeclaration, KindImportSpecifier,
+		KindIndexSignature, KindInterfaceDeclaration, KindJSDocSignature, KindJSDocTypeLiteral,
+		KindJsxAttribute, KindJsxAttributes, KindJsxSpreadAttribute, KindMappedType, KindMethodDeclaration,
+		KindMethodSignature, KindModuleDeclaration, KindNamedTupleMember, KindNamespaceExport, KindNamespaceExportDeclaration,
+		KindNamespaceImport, KindNewExpression, KindNoSubstitutionTemplateLiteral, KindNumericLiteral, KindObjectLiteralExpression,
+		KindParameter, KindPropertyAccessExpression, KindPropertyAssignment, KindPropertyDeclaration, KindPropertySignature,
+		KindSetAccessor, KindShorthandPropertyAssignment, KindSourceFile, KindSpreadAssignment, KindStringLiteral,
+		KindTypeAliasDeclaration, KindJSTypeAliasDeclaration, KindTypeLiteral, KindTypeParameter, KindVariableDeclaration:
+		return true
+	}
+	return false
+}
+
+func IndexOfNode(nodes []*Node, node *Node) int {
+	index, ok := slices.BinarySearchFunc(nodes, node, compareNodePositions)
+	if ok {
+		return index
+	}
+	return -1
+}
+
+func compareNodePositions(n1, n2 *Node) int {
+	return n1.Pos() - n2.Pos()
+}

internal/checker/checker.go

@@ -7713,7 +7713,7 @@ func (c *Checker) createArrayLiteralType(t *Type) *Type {
 
 func isSpreadIntoCallOrNew(node *ast.Node) bool {
 	parent := ast.WalkUpParenthesizedExpressions(node.Parent)
-	return ast.IsSpreadElement(parent) && isCallOrNewExpression(parent.Parent)
+	return ast.IsSpreadElement(parent) && ast.IsCallOrNewExpression(parent.Parent)
 }
 
 func (c *Checker) checkQualifiedName(node *ast.Node, checkMode CheckMode) *Type {
@@ -7953,7 +7953,7 @@ func (c *Checker) checkDeprecatedSignature(sig *Signature, node *ast.Node) {
 	}
 	if sig.declaration != nil && sig.declaration.Flags&ast.NodeFlagsDeprecated != 0 {
 		suggestionNode := c.getDeprecatedSuggestionNode(node)
-		name := tryGetPropertyAccessOrIdentifierToString(getInvokedExpression(node))
+		name := tryGetPropertyAccessOrIdentifierToString(ast.GetInvokedExpression(node))
 		c.addDeprecatedSuggestionWithSignature(suggestionNode, sig.declaration, name, c.signatureToString(sig))
 	}
 }
@@ -8419,7 +8419,7 @@ type CallState struct {
 func (c *Checker) resolveCall(node *ast.Node, signatures []*Signature, candidatesOutArray *[]*Signature, checkMode CheckMode, callChainFlags SignatureFlags, headMessage *diagnostics.Message) *Signature {
 	isTaggedTemplate := node.Kind == ast.KindTaggedTemplateExpression
 	isDecorator := node.Kind == ast.KindDecorator
-	isJsxOpeningOrSelfClosingElement := isJsxOpeningLikeElement(node)
+	isJsxOpeningOrSelfClosingElement := ast.IsJsxOpeningLikeElement(node)
 	isInstanceof := node.Kind == ast.KindBinaryExpression
 	reportErrors := !c.isInferencePartiallyBlocked && candidatesOutArray == nil
 	var s CallState
@@ -8725,7 +8725,7 @@ func (c *Checker) hasCorrectArity(node *ast.Node, args []*ast.Node, signature *S
 		argCount = c.getDecoratorArgumentCount(node, signature)
 	case ast.IsBinaryExpression(node):
 		argCount = 1
-	case isJsxOpeningLikeElement(node):
+	case ast.IsJsxOpeningLikeElement(node):
 		callIsIncomplete = node.Attributes().End() == node.End()
 		if callIsIncomplete {
 			return true
@@ -8845,7 +8845,7 @@ func (c *Checker) checkTypeArguments(signature *Signature, typeArgumentNodes []*
 }
 
 func (c *Checker) isSignatureApplicable(node *ast.Node, args []*ast.Node, signature *Signature, relation *Relation, checkMode CheckMode, reportErrors bool, inferenceContext *InferenceContext, diagnosticOutput *[]*ast.Diagnostic) bool {
-	if isJsxOpeningLikeElement(node) {
+	if ast.IsJsxOpeningLikeElement(node) {
 		return c.checkApplicableSignatureForJsxOpeningLikeElement(node, signature, relation, checkMode, reportErrors, diagnosticOutput)
 	}
 	thisType := c.getThisTypeOfSignature(signature)
@@ -8986,7 +8986,7 @@ func (c *Checker) getEffectiveCheckNode(argument *ast.Node) *ast.Node {
 }
 
 func (c *Checker) inferTypeArguments(node *ast.Node, signature *Signature, args []*ast.Node, checkMode CheckMode, context *InferenceContext) []*Type {
-	if isJsxOpeningLikeElement(node) {
+	if ast.IsJsxOpeningLikeElement(node) {
 		return c.inferJsxTypeArguments(node, signature, checkMode, context)
 	}
 	// If a contextual type is available, infer from that type to the return type of the call expression. For
@@ -10835,7 +10835,7 @@ func (c *Checker) isMethodAccessForCall(node *ast.Node) bool {
 	for ast.IsParenthesizedExpression(node.Parent) {
 		node = node.Parent
 	}
-	return isCallOrNewExpression(node.Parent) && node.Parent.Expression() == node
+	return ast.IsCallOrNewExpression(node.Parent) && node.Parent.Expression() == node
 }
 
 // Lookup the private identifier lexically.
@@ -11051,7 +11051,7 @@ func (c *Checker) isUncalledFunctionReference(node *ast.Node, symbol *ast.Symbol
 			parent = node.Parent
 		}
 		if ast.IsCallLikeExpression(parent) {
-			return isCallOrNewExpression(parent) && ast.IsIdentifier(node) && c.hasMatchingArgument(parent, node)
+			return ast.IsCallOrNewExpression(parent) && ast.IsIdentifier(node) && c.hasMatchingArgument(parent, node)
 		}
 		return core.Every(symbol.Declarations, func(d *ast.Node) bool {
 			return !ast.IsFunctionLike(d) || c.IsDeprecatedDeclaration(d)
@@ -14179,7 +14179,7 @@ func (c *Checker) getTargetOfAliasLikeExpression(expression *ast.Node, dontResol
 }
 
 func (c *Checker) getTargetOfNamespaceExportDeclaration(node *ast.Node, dontResolveAlias bool) *ast.Symbol {
-	if canHaveSymbol(node.Parent) {
+	if ast.CanHaveSymbol(node.Parent) {
 		resolved := c.resolveExternalModuleSymbol(node.Parent.Symbol(), dontResolveAlias)
 		c.markSymbolOfAliasDeclarationIfTypeOnly(node, nil /*immediateTarget*/, resolved, false /*overwriteEmpty*/, nil, "")
 		return resolved
@@ -26275,18 +26275,6 @@ func (c *Checker) markPropertyAsReferenced(prop *ast.Symbol, nodeForCheckWriteOn
 	c.symbolReferenceLinks.Get(target).referenceKinds |= ast.SymbolFlagsAll
 }
 
-func (c *Checker) GetExpandedParameters(signature *Signature /* !!! skipUnionExpanding */) []*ast.Symbol {
-	if signatureHasRestParameter(signature) {
-		restIndex := len(signature.parameters) - 1
-		restSymbol := signature.parameters[restIndex]
-		restType := c.getTypeOfSymbol(restSymbol)
-		if isTupleType(restType) {
-			return c.expandSignatureParametersWithTupleMembers(signature, restType.AsTypeReference(), restIndex, restSymbol)
-		}
-	}
-	return signature.parameters
-}
-
 func (c *Checker) expandSignatureParametersWithTupleMembers(signature *Signature, restType *TypeReference, restIndex int, restSymbol *ast.Symbol) []*ast.Symbol {
 	elementTypes := c.getTypeArguments(restType.AsType())
 	elementInfos := restType.TargetTupleType().elementInfos
@@ -26765,7 +26753,7 @@ func (c *Checker) markLinkedReferences(location *ast.Node, hint ReferenceHint, p
 			c.markExportAssignmentAliasReferenced(location)
 			return
 		}
-		if isJsxOpeningLikeElement(location) || ast.IsJsxOpeningFragment(location) {
+		if ast.IsJsxOpeningLikeElement(location) || ast.IsJsxOpeningFragment(location) {
 			c.markJsxAliasReferenced(location)
 			return
 		}
@@ -26930,7 +26918,7 @@ func (c *Checker) markJsxAliasReferenced(node *ast.Node /*JsxOpeningLikeElement
 	jsxFactoryRefErr := core.IfElse(c.compilerOptions.Jsx == core.JsxEmitReact, diagnostics.This_JSX_tag_requires_0_to_be_in_scope_but_it_could_not_be_found, nil)
 	jsxFactoryNamespace := c.getJsxNamespace(node)
 	jsxFactoryLocation := node
-	if isJsxOpeningLikeElement(node) {
+	if ast.IsJsxOpeningLikeElement(node) {
 		jsxFactoryLocation = node.TagName()
 	}
 	// allow null as jsxFragmentFactory
@@ -27572,7 +27560,7 @@ func (c *Checker) getContextualType(node *ast.Node, contextFlags ContextFlags) *
 		return c.getContextualType(parent.Parent, contextFlags)
 	case ast.KindArrayLiteralExpression:
 		t := c.getApparentTypeOfContextualType(parent, contextFlags)
-		elementIndex := indexOfNode(parent.AsArrayLiteralExpression().Elements.Nodes, node)
+		elementIndex := ast.IndexOfNode(parent.AsArrayLiteralExpression().Elements.Nodes, node)
 		firstSpreadIndex, lastSpreadIndex := c.getSpreadIndices(parent)
 		return c.getContextualTypeForElementExpression(t, elementIndex, len(parent.AsArrayLiteralExpression().Elements.Nodes), firstSpreadIndex, lastSpreadIndex)
 	case ast.KindConditionalExpression:
@@ -27975,7 +27963,7 @@ func (c *Checker) getContextualTypeForArgumentAtIndex(callTarget *ast.Node, argI
 	} else {
 		signature = c.getResolvedSignature(callTarget, nil, CheckModeNormal)
 	}
-	if isJsxOpeningLikeElement(callTarget) && argIndex == 0 {
+	if ast.IsJsxOpeningLikeElement(callTarget) && argIndex == 0 {
 		return c.getEffectiveFirstArgumentForJsxSignature(signature, callTarget)
 	}
 	restIndex := len(signature.parameters) - 1
@@ -28229,7 +28217,7 @@ func (c *Checker) getEffectiveCallArguments(node *ast.Node) []*ast.Node {
 	case ast.IsBinaryExpression(node):
 		// Handles instanceof operator
 		return []*ast.Node{node.AsBinaryExpression().Left}
-	case isJsxOpeningLikeElement(node):
+	case ast.IsJsxOpeningLikeElement(node):
 		if len(node.Attributes().AsJsxAttributes().Properties.Nodes) != 0 || (ast.IsJsxOpeningElement(node) && len(node.Parent.Children().Nodes) != 0) {
 			return []*ast.Node{node.Attributes()}
 		}

internal/checker/exports.go

@@ -85,3 +85,35 @@ func (c *Checker) GetEffectiveDeclarationFlags(n *ast.Node, flagsToCheck ast.Mod
 func (c *Checker) GetBaseConstraintOfType(t *Type) *Type {
 	return c.getBaseConstraintOfType(t)
 }
+
+func (c *Checker) GetTypePredicateOfSignature(sig *Signature) *TypePredicate {
+	return c.getTypePredicateOfSignature(sig)
+}
+
+func IsTupleType(t *Type) bool {
+	return isTupleType(t)
+}
+
+func (c *Checker) GetReturnTypeOfSignature(sig *Signature) *Type {
+	return c.getReturnTypeOfSignature(sig)
+}
+
+func (c *Checker) HasEffectiveRestParameter(signature *Signature) bool {
+	return c.hasEffectiveRestParameter(signature)
+}
+
+func (c *Checker) GetLocalTypeParametersOfClassOrInterfaceOrTypeAlias(symbol *ast.Symbol) []*Type {
+	return c.getLocalTypeParametersOfClassOrInterfaceOrTypeAlias(symbol)
+}
+
+func (c *Checker) GetContextualTypeForObjectLiteralElement(element *ast.Node, contextFlags ContextFlags) *Type {
+	return c.getContextualTypeForObjectLiteralElement(element, contextFlags)
+}
+
+func (c *Checker) TypePredicateToString(t *TypePredicate) string {
+	return c.typePredicateToString(t)
+}
+
+func (c *Checker) GetExpandedParameters(signature *Signature, skipUnionExpanding bool) [][]*ast.Symbol {
+	return c.getExpandedParameters(signature, skipUnionExpanding)
+}

internal/checker/jsx.go

@@ -119,7 +119,7 @@ func (c *Checker) checkJsxAttributes(node *ast.Node, checkMode CheckMode) *Type
 }
 
 func (c *Checker) checkJsxOpeningLikeElementOrOpeningFragment(node *ast.Node) {
-	isNodeOpeningLikeElement := isJsxOpeningLikeElement(node)
+	isNodeOpeningLikeElement := ast.IsJsxOpeningLikeElement(node)
 	if isNodeOpeningLikeElement {
 		c.checkGrammarJsxElement(node)
 	}

internal/checker/relater.go

@@ -2693,7 +2693,7 @@ func (r *Relater) hasExcessProperties(source *Type, target *Type, reportErrors b
 					if r.errorNode == nil {
 						panic("No errorNode in hasExcessProperties")
 					}
-					if ast.IsJsxAttributes(r.errorNode) || isJsxOpeningLikeElement(r.errorNode) || isJsxOpeningLikeElement(r.errorNode.Parent) {
+					if ast.IsJsxAttributes(r.errorNode) || ast.IsJsxOpeningLikeElement(r.errorNode) || ast.IsJsxOpeningLikeElement(r.errorNode.Parent) {
 						// JsxAttributes has an object-literal flag and undergo same type-assignablity check as normal object-literal.
 						// However, using an object-literal error message will be very confusing to the users so we give different a message.
 						if prop.ValueDeclaration != nil && ast.IsJsxAttribute(prop.ValueDeclaration) && ast.GetSourceFileOfNode(r.errorNode) == ast.GetSourceFileOfNode(prop.ValueDeclaration.Name()) {

internal/checker/services.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/microsoft/typescript-go/internal/ast"
 	"github.com/microsoft/typescript-go/internal/core"
+	"github.com/microsoft/typescript-go/internal/printer"
 )
 
 func (c *Checker) GetSymbolsInScope(location *ast.Node, meaning ast.SymbolFlags) []*ast.Symbol {
@@ -299,10 +300,20 @@ func runWithInferenceBlockedFromSourceNode[T any](c *Checker, node *ast.Node, fn
 	return result
 }
 
-func runWithoutResolvedSignatureCaching[T any](c *Checker, node *ast.Node, fn func() T) T {
-	ancestorNode := ast.FindAncestor(node, func(n *ast.Node) bool {
-		return ast.IsCallLikeOrFunctionLikeExpression(n)
+func GetResolvedSignatureForSignatureHelp(node *ast.Node, argumentCount int, c *Checker) (*Signature, []*Signature) {
+	type result struct {
+		signature  *Signature
+		candidates []*Signature
+	}
+	res := runWithoutResolvedSignatureCaching(c, node, func() result {
+		signature, candidates := c.getResolvedSignatureWorker(node, CheckModeIsForSignatureHelp, argumentCount)
+		return result{signature, candidates}
 	})
+	return res.signature, res.candidates
+}
+
+func runWithoutResolvedSignatureCaching[T any](c *Checker, node *ast.Node, fn func() T) T {
+	ancestorNode := ast.FindAncestor(node, ast.IsCallLikeOrFunctionLikeExpression)
 	if ancestorNode != nil {
 		cachedResolvedSignatures := make(map[*SignatureLinks]*Signature)
 		cachedTypes := make(map[*ValueSymbolLinks]*Type)
@@ -506,3 +517,15 @@ func (c *Checker) GetConstantValue(node *ast.Node) any {
 
 	return nil
 }
+
+func (c *Checker) getResolvedSignatureWorker(node *ast.Node, checkMode CheckMode, argumentCount int) (*Signature, []*Signature) {
+	parsedNode := printer.NewEmitContext().ParseNode(node)
+	c.apparentArgumentCount = &argumentCount
+	candidatesOutArray := &[]*Signature{}
+	var res *Signature
+	if parsedNode != nil {
+		res = c.getResolvedSignature(parsedNode, candidatesOutArray, checkMode)
+	}
+	c.apparentArgumentCount = nil
+	return res, *candidatesOutArray
+}

internal/checker/types.go

@@ -588,6 +588,10 @@ func (t *Type) Flags() TypeFlags {
 	return t.flags
 }
 
+func (t *Type) ObjectFlags() ObjectFlags {
+	return t.objectFlags
+}
+
 // Casts for concrete struct types
 
 func (t *Type) AsIntrinsicType() *IntrinsicType             { return t.data.(*IntrinsicType) }
@@ -940,6 +944,8 @@ type TupleElementInfo struct {
 	labeledDeclaration *ast.Node // NamedTupleMember | ParameterDeclaration | nil
 }
 
+func (t *TupleElementInfo) TupleElementFlags() ElementFlags { return t.flags }
+
 type TupleType struct {
 	InterfaceType
 	elementInfos  []TupleElementInfo
@@ -949,6 +955,15 @@ type TupleType struct {
 	readonly      bool
 }
 
+func (t *TupleType) FixedLength() int { return t.fixedLength }
+func (t *TupleType) ElementFlags() []ElementFlags {
+	elementFlags := make([]ElementFlags, len(t.elementInfos))
+	for i, info := range t.elementInfos {
+		elementFlags[i] = info.flags
+	}
+	return elementFlags
+}
+
 // SingleSignatureType
 
 type SingleSignatureType struct {
@@ -1148,6 +1163,22 @@ type Signature struct {
 	composite                *CompositeSignature
 }
 
+func (s *Signature) TypeParameters() []*Type {
+	return s.typeParameters
+}
+
+func (s *Signature) Declaration() *ast.Node {
+	return s.declaration
+}
+
+func (s *Signature) Target() *Signature {
+	return s.target
+}
+
+func (s *Signature) ThisParameter() *ast.Symbol {
+	return s.thisParameter
+}
+
 type CompositeSignature struct {
 	isUnion    bool         // True for union, false for intersection
 	signatures []*Signature // Individual signatures