diff --git a/internal/ast/utilities.go b/internal/ast/utilities.go
index 53ee669474..ffe9baee60 100644
--- a/internal/ast/utilities.go
+++ b/internal/ast/utilities.go
@@ -2792,3 +2792,12 @@ func IsClassMemberModifier(token Kind) bool {
 func IsParameterPropertyModifier(kind Kind) bool {
 	return ModifierToFlag(kind)&ModifierFlagsParameterPropertyModifier != 0
 }
+
+func ForEachChildAndJSDoc(node *Node, sourceFile *SourceFile, v Visitor) bool {
+	if node.Flags&NodeFlagsHasJSDoc != 0 {
+		if visitNodes(v, node.JSDoc(sourceFile)) {
+			return true
+		}
+	}
+	return node.ForEachChild(v)
+}
diff --git a/internal/ls/completions.go b/internal/ls/completions.go
index 605ff714f7..b003ed90d3 100644
--- a/internal/ls/completions.go
+++ b/internal/ls/completions.go
@@ -121,7 +121,7 @@ const (
 	SortTextJavascriptIdentifiers            sortText = "18"
 )
 
-func deprecateSortText(original sortText) sortText {
+func DeprecateSortText(original sortText) sortText {
 	return "z" + original
 }
 
@@ -910,6 +910,7 @@ func (l *LanguageService) getCompletionEntriesFromSymbols(
 	closestSymbolDeclaration := getClosestSymbolDeclaration(data.contextToken, data.location)
 	useSemicolons := probablyUsesSemicolons(file)
 	typeChecker := program.GetTypeChecker()
+	isMemberCompletion := isMemberCompletionKind(data.completionKind)
 	// Tracks unique names.
 	// Value is set to false for global variables or completions from external module exports, because we can have multiple of those;
 	// true otherwise. Based on the order we add things we will always see locals first, then globals, then module exports.
@@ -944,7 +945,7 @@ func (l *LanguageService) getCompletionEntriesFromSymbols(
 
 		var sortText sortText
 		if isDeprecated(symbol, typeChecker) {
-			sortText = deprecateSortText(originalSortText)
+			sortText = DeprecateSortText(originalSortText)
 		} else {
 			sortText = originalSortText
 		}
@@ -963,12 +964,13 @@ func (l *LanguageService) getCompletionEntriesFromSymbols(
 			compilerOptions,
 			preferences,
 			clientOptions,
+			isMemberCompletion,
 		)
 		if entry == nil {
 			continue
 		}
 
-		/** True for locals; false for globals, module exports from other files, `this.` completions. */
+		// True for locals; false for globals, module exports from other files, `this.` completions.
 		shouldShadowLaterSymbols := (origin == nil || originIsTypeOnlyAlias(origin)) &&
 			!(symbol.Parent == nil &&
 				!core.Some(symbol.Declarations, func(d *ast.Node) bool { return ast.GetSourceFileOfNode(d) == file }))
@@ -1028,6 +1030,7 @@ func (l *LanguageService) createCompletionItem(
 	compilerOptions *core.CompilerOptions,
 	preferences *UserPreferences,
 	clientOptions *lsproto.CompletionClientCapabilities,
+	isMemberCompletion bool,
 ) *lsproto.CompletionItem {
 	contextToken := data.contextToken
 	var insertText string
@@ -1250,6 +1253,8 @@ func (l *LanguageService) createCompletionItem(
 		}
 	}
 
+	// Commit characters
+
 	elementKind := getSymbolKind(typeChecker, symbol, data.location)
 	kind := getCompletionsSymbolKind(elementKind)
 	var commitCharacters *[]string
@@ -1262,10 +1267,77 @@ func (l *LanguageService) createCompletionItem(
 		// Otherwise use the completion list default.
 	}
 
+	// Text edit
+
+	var textEdit *lsproto.TextEditOrInsertReplaceEdit
+	if replacementSpan != nil {
+		textEdit = &lsproto.TextEditOrInsertReplaceEdit{
+			TextEdit: &lsproto.TextEdit{
+				NewText: core.IfElse(insertText == "", name, insertText),
+				Range:   *replacementSpan,
+			},
+		}
+	} else {
+		// Ported from vscode ts extension.
+		optionalReplacementSpan := getOptionalReplacementSpan(data.location, file)
+		if optionalReplacementSpan != nil && ptrIsTrue(clientOptions.CompletionItem.InsertReplaceSupport) {
+			insertRange := l.createLspRangeFromBounds(optionalReplacementSpan.Pos(), position, file)
+			replaceRange := l.createLspRangeFromBounds(optionalReplacementSpan.Pos(), optionalReplacementSpan.End(), file)
+			textEdit = &lsproto.TextEditOrInsertReplaceEdit{
+				InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+					NewText: core.IfElse(insertText == "", name, insertText),
+					Insert:  *insertRange,
+					Replace: *replaceRange,
+				},
+			}
+		}
+	}
+
+	// Filter text
+
+	// Ported from vscode ts extension.
+	wordRange, wordStart := getWordRange(file, position)
+	if filterText == "" {
+		filterText = getFilterText(file, position, insertText, name, isMemberCompletion, isSnippet, wordStart)
+	}
+	if isMemberCompletion && !isSnippet {
+		accessorRange, accessorText := getDotAccessorContext(file, position)
+		if accessorText != "" {
+			filterText = accessorText + core.IfElse(insertText != "", insertText, name)
+			if textEdit == nil {
+				insertText = filterText
+				if wordRange != nil && ptrIsTrue(clientOptions.CompletionItem.InsertReplaceSupport) {
+					textEdit = &lsproto.TextEditOrInsertReplaceEdit{
+						InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+							NewText: insertText,
+							Insert: *l.createLspRangeFromBounds(
+								accessorRange.Pos(),
+								accessorRange.End(),
+								file),
+							Replace: *l.createLspRangeFromBounds(
+								min(accessorRange.Pos(), wordRange.Pos()),
+								accessorRange.End(),
+								file),
+						},
+					}
+				} else {
+					textEdit = &lsproto.TextEditOrInsertReplaceEdit{
+						TextEdit: &lsproto.TextEdit{
+							NewText: insertText,
+							Range:   *l.createLspRangeFromBounds(accessorRange.Pos(), accessorRange.End(), file),
+						},
+					}
+				}
+			}
+		}
+	}
+
+	// Adjustements based on kind modifiers.
+
 	kindModifiers := getSymbolModifiers(typeChecker, symbol)
 	var tags *[]lsproto.CompletionItemTag
 	var detail *string
-	// Copied from vscode ts extension.
+	// Copied from vscode ts extension: `MyCompletionItem.constructor`.
 	if kindModifiers.Has(ScriptElementKindModifierOptional) {
 		if insertText == "" {
 			insertText = name
@@ -1302,17 +1374,6 @@ func (l *LanguageService) createCompletionItem(
 		insertTextFormat = ptrTo(lsproto.InsertTextFormatPlainText)
 	}
 
-	var textEdit *lsproto.TextEditOrInsertReplaceEdit
-	if replacementSpan != nil {
-		textEdit = &lsproto.TextEditOrInsertReplaceEdit{
-			TextEdit: &lsproto.TextEdit{
-				NewText: core.IfElse(insertText == "", name, insertText),
-				Range:   *replacementSpan,
-			},
-		}
-	}
-	// !!! adjust text edit like vscode does when Strada's `isMemberCompletion` is true
-
 	return &lsproto.CompletionItem{
 		Label:            name,
 		LabelDetails:     labelDetails,
@@ -1340,6 +1401,118 @@ func isRecommendedCompletionMatch(localSymbol *ast.Symbol, recommendedCompletion
 		localSymbol.Flags&ast.SymbolFlagsExportValue != 0 && typeChecker.GetExportSymbolOfSymbol(localSymbol) == recommendedCompletion
 }
 
+// Ported from vscode's `USUAL_WORD_SEPARATORS`.
+var wordSeparators = core.NewSetFromItems(
+	'`', '~', '!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '-', '=', '+', '[', '{', ']', '}', '\\', '|',
+	';', ':', '\'', '"', ',', '.', '<', '>', '/', '?',
+)
+
+// Finds the range of the word that ends at the given position.
+// e.g. for "abc def.ghi|jkl", the word range is "ghi" and the word start is 'g'.
+func getWordRange(sourceFile *ast.SourceFile, position int) (wordRange *core.TextRange, wordStart rune) {
+	// !!! Port other case of vscode's `DEFAULT_WORD_REGEXP` that covers words that start like numbers, e.g. -123.456abcd.
+	text := sourceFile.Text()[:position]
+	totalSize := 0
+	var firstRune rune
+	for r, size := utf8.DecodeLastRuneInString(text); size != 0; r, size = utf8.DecodeLastRuneInString(text[:len(text)-size]) {
+		if wordSeparators.Has(r) || unicode.IsSpace(r) {
+			break
+		}
+		totalSize += size
+		firstRune = r
+	}
+	// If word starts with `@`, disregard this first character.
+	if firstRune == '@' {
+		totalSize -= 1
+		firstRune, _ = utf8.DecodeRuneInString(text[len(text)-totalSize:])
+	}
+	if totalSize == 0 {
+		return nil, firstRune
+	}
+	textRange := core.NewTextRange(position-totalSize, position)
+	return &textRange, firstRune
+}
+
+// Ported from vscode ts extension: `getFilterText`.
+func getFilterText(
+	file *ast.SourceFile,
+	position int,
+	insertText string,
+	label string,
+	isMemberCompletion bool,
+	isSnippet bool,
+	wordStart rune,
+) string {
+	// Private field completion.
+	if strings.HasPrefix(label, "#") {
+		// !!! document theses cases
+		if insertText != "" {
+			if strings.HasPrefix(insertText, "this.#") {
+				if wordStart == '#' {
+					return insertText
+				} else {
+					return strings.TrimPrefix(insertText, "this.#")
+				}
+			}
+		} else {
+			if wordStart == '#' {
+				return ""
+			} else {
+				return strings.TrimPrefix(label, "#")
+			}
+		}
+	}
+
+	// For `this.` completions, generally don't set the filter text since we don't want them to be overly prioritized. microsoft/vscode#74164
+	if strings.HasPrefix(insertText, "this.") {
+		return ""
+	}
+
+	// Handle the case:
+	// ```
+	// const xyz = { 'ab c': 1 };
+	// xyz.ab|
+	// ```
+	// In which case we want to insert a bracket accessor but should use `.abc` as the filter text instead of
+	// the bracketed insert text.
+	if strings.HasPrefix(insertText, "[") {
+		if strings.HasPrefix(insertText, `['`) && strings.HasSuffix(insertText, `']`) {
+			return "." + strings.TrimPrefix(strings.TrimSuffix(insertText, `']`), `['`)
+		}
+		if strings.HasPrefix(insertText, `["`) && strings.HasSuffix(insertText, `"]`) {
+			return "." + strings.TrimPrefix(strings.TrimSuffix(insertText, `"]`), `["`)
+		}
+		return insertText
+	}
+
+	// In all other cases, fall back to using the insertText.
+	return insertText
+}
+
+// Ported from vscode's `provideCompletionItems`.
+func getDotAccessorContext(file *ast.SourceFile, position int) (acessorRange *core.TextRange, accessorText string) {
+	text := file.Text()[:position]
+	totalSize := 0
+	for r, size := utf8.DecodeLastRuneInString(text); size != 0; r, size = utf8.DecodeLastRuneInString(text[:len(text)-size]) {
+		if !unicode.IsSpace(r) {
+			break
+		}
+		totalSize += size
+		text = text[:len(text)-size]
+	}
+	if strings.HasSuffix(text, "?.") {
+		totalSize += 2
+		newRange := core.NewTextRange(position-totalSize, position)
+		return &newRange, file.Text()[position-totalSize : position]
+	}
+	if strings.HasSuffix(text, ".") {
+		totalSize += 1
+		newRange := core.NewTextRange(position-totalSize, position)
+		return &newRange, file.Text()[position-totalSize : position]
+	}
+	return nil, ""
+}
+
 func strPtrTo(v string) *string {
 	if v == "" {
 		return nil
@@ -2319,3 +2492,19 @@ func getJSCompletionEntries(
 	}
 	return sortedEntries
 }
+
+func getOptionalReplacementSpan(location *ast.Node, file *ast.SourceFile) *core.TextRange {
+	// StringLiteralLike locations are handled separately in stringCompletions.ts
+	if location != nil && location.Kind == ast.KindIdentifier {
+		start := astnav.GetStartOfNode(location, file, false /*includeJSDoc*/)
+		textRange := core.NewTextRange(start, location.End())
+		return &textRange
+	}
+	return nil
+}
+
+func isMemberCompletionKind(kind CompletionKind) bool {
+	return kind == CompletionKindObjectPropertyDeclaration ||
+		kind == CompletionKindMemberLike ||
+		kind == CompletionKindPropertyAccess
+}
diff --git a/internal/ls/completions_test.go b/internal/ls/completions_test.go
index 883844835f..31675cbf43 100644
--- a/internal/ls/completions_test.go
+++ b/internal/ls/completions_test.go
@@ -7,6 +7,7 @@ import (
 	"github.com/microsoft/typescript-go/internal/core"
 	"github.com/microsoft/typescript-go/internal/ls"
 	"github.com/microsoft/typescript-go/internal/lsp/lsproto"
+	"github.com/microsoft/typescript-go/internal/testutil/lstestutil"
 	"github.com/microsoft/typescript-go/internal/testutil/projecttestutil"
 	"gotest.tools/v3/assert"
 )
@@ -15,11 +16,12 @@ var defaultCommitCharacters = []string{".", ",", ";"}
 
 type testCase struct {
 	name     string
-	content  string
-	position int
-	expected *lsproto.CompletionList
+	files    map[string]string
+	expected map[string]*lsproto.CompletionList
 }
 
+const mainFileName = "/index.ts"
+
 func TestCompletions(t *testing.T) {
 	t.Parallel()
 	if !bundled.Embedded {
@@ -27,95 +29,763 @@ func TestCompletions(t *testing.T) {
 		// Just skip this for now.
 		t.Skip("bundled files are not embedded")
 	}
+
+	itemDefaults := &lsproto.CompletionItemDefaults{
+		CommitCharacters: &defaultCommitCharacters,
+	}
+	insertTextFormatPlainText := ptrTo(lsproto.InsertTextFormatPlainText)
+	sortTextLocationPriority := ptrTo(string(ls.SortTextLocationPriority))
+	sortTextLocalDeclarationPriority := ptrTo(string(ls.SortTextLocalDeclarationPriority))
+	sortTextDeprecatedLocationPriority := ptrTo(string(ls.DeprecateSortText(ls.SortTextLocationPriority)))
+	fieldKind := ptrTo(lsproto.CompletionItemKindField)
+	methodKind := ptrTo(lsproto.CompletionItemKindMethod)
+	functionKind := ptrTo(lsproto.CompletionItemKindFunction)
+	variableKind := ptrTo(lsproto.CompletionItemKindVariable)
+
+	stringMembers := []*lsproto.CompletionItem{
+		{Label: "charAt", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "charCodeAt", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "concat", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "indexOf", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "lastIndexOf", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "length", Kind: fieldKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "localeCompare", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "match", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "replace", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "search", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "slice", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "split", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "substring", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toLocaleLowerCase", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toLocaleUpperCase", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toLowerCase", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toString", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toUpperCase", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "trim", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "valueOf", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "substr", Kind: methodKind, SortText: sortTextDeprecatedLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+	}
+
+	arrayMembers := []*lsproto.CompletionItem{
+		{Label: "concat", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "every", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "filter", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "forEach", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "indexOf", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "join", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "lastIndexOf", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "length", Kind: fieldKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "map", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "pop", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "push", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "reduce", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "reduceRight", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "reverse", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "shift", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "slice", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "some", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "sort", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "splice", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toLocaleString", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "toString", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+		{Label: "unshift", Kind: methodKind, SortText: sortTextLocationPriority, InsertTextFormat: insertTextFormatPlainText},
+	}
+
 	testCases := []testCase{
 		{
 			name: "basicInterfaceMembers",
-			content: `export {};
+			files: map[string]string{
+				mainFileName: `export {};
 interface Point {
     x: number;
     y: number;
 }
 declare const p: Point;
-p.`,
-			position: 87,
-			expected: &lsproto.CompletionList{
-				IsIncomplete: false,
-				ItemDefaults: &lsproto.CompletionItemDefaults{
-					CommitCharacters: &defaultCommitCharacters,
-				},
-				Items: []*lsproto.CompletionItem{
-					{
-						Label:            "x",
-						Kind:             ptrTo(lsproto.CompletionItemKindField),
-						SortText:         ptrTo(string(ls.SortTextLocationPriority)),
-						InsertTextFormat: ptrTo(lsproto.InsertTextFormatPlainText),
+p./*a*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"a": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{
+						{
+							Label:            "x",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".x"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "x",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 2},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 2},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "y",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".y"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "y",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 2},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 2},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+								},
+							},
+						},
 					},
-					{
-						Label:            "y",
-						Kind:             ptrTo(lsproto.CompletionItemKindField),
-						SortText:         ptrTo(string(ls.SortTextLocationPriority)),
-						InsertTextFormat: ptrTo(lsproto.InsertTextFormatPlainText),
+				},
+			},
+		},
+		{
+			name: "basicInterfaceMembersOptional",
+			files: map[string]string{
+				"/tsconfig.json": `{ "compilerOptions": { "strict": true } }`,
+				mainFileName: `export {};
+interface Point {
+    x: number;
+    y: number;
+}
+declare const p: Point | undefined;
+p./*a*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"a": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{
+						{
+							Label:            "x",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".?.x"),
+							InsertText:       ptrTo("?.x"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								TextEdit: &lsproto.TextEdit{
+									NewText: "?.x",
+									Range: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 1},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "y",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".?.y"),
+							InsertText:       ptrTo("?.y"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								TextEdit: &lsproto.TextEdit{
+									NewText: "?.y",
+									Range: lsproto.Range{
+										Start: lsproto.Position{Line: 6, Character: 1},
+										End:   lsproto.Position{Line: 6, Character: 2},
+									},
+								},
+							},
+						},
 					},
 				},
 			},
 		},
 		{
 			name: "objectLiteralType",
-			content: `export {};
+			files: map[string]string{
+				mainFileName: `export {};
 let x = { foo: 123 };
-x.`,
-			position: 35,
-			expected: &lsproto.CompletionList{
-				IsIncomplete: false,
-				ItemDefaults: &lsproto.CompletionItemDefaults{
-					CommitCharacters: &defaultCommitCharacters,
+x./*a*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"a": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{
+						{
+							Label:            "foo",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".foo"),
+							InsertTextFormat: ptrTo(lsproto.InsertTextFormatPlainText),
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "foo",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 2, Character: 2},
+										End:   lsproto.Position{Line: 2, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 2, Character: 2},
+										End:   lsproto.Position{Line: 2, Character: 2},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "basicClassMembers",
+			files: map[string]string{
+				mainFileName: `
+class n {
+    constructor (public x: number, public y: number, private z: string) { }
+}
+var t = new n(0, 1, '');t./*a*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"a": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{
+						{
+							Label:            "x",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".x"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "x",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 3, Character: 26},
+										End:   lsproto.Position{Line: 3, Character: 26},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 3, Character: 26},
+										End:   lsproto.Position{Line: 3, Character: 26},
+									},
+								},
+							},
+						},
+						{
+							Label:            "y",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".y"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "y",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 3, Character: 26},
+										End:   lsproto.Position{Line: 3, Character: 26},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 3, Character: 26},
+										End:   lsproto.Position{Line: 3, Character: 26},
+									},
+								},
+							},
+						},
+					},
 				},
-				Items: []*lsproto.CompletionItem{
-					{
-						Label:            "foo",
-						Kind:             ptrTo(lsproto.CompletionItemKindField),
-						SortText:         ptrTo(string(ls.SortTextLocationPriority)),
-						InsertTextFormat: ptrTo(lsproto.InsertTextFormatPlainText),
+			},
+		},
+		{
+			name: "cloduleAsBaseClass",
+			files: map[string]string{
+				mainFileName: `
+class A {
+    constructor(x: number) { }
+    foo() { }
+    static bar() { }
+}
+
+module A {
+    export var x = 1;
+    export function baz() { }
+}
+
+class D extends A {
+    constructor() {
+        super(1);
+    }
+    foo2() { }
+    static bar2() { }
+}
+
+D./*a*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"a": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{ // !!! `funcionMembersPlus`
+						{
+							Label:            "bar",
+							Kind:             methodKind,
+							SortText:         sortTextLocalDeclarationPriority,
+							FilterText:       ptrTo(".bar"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "bar",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "bar2",
+							Kind:             methodKind,
+							SortText:         sortTextLocalDeclarationPriority,
+							FilterText:       ptrTo(".bar2"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "bar2",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "apply",
+							Kind:             methodKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".apply"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "apply",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "arguments",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".arguments"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "arguments",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "baz",
+							Kind:             functionKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".baz"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "baz",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "bind",
+							Kind:             methodKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".bind"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "bind",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "call",
+							Kind:             methodKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".call"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "call",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "caller",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".caller"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "caller",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "length",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".length"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "length",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "prototype",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".prototype"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "prototype",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "toString",
+							Kind:             methodKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".toString"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "toString",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "x",
+							Kind:             variableKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".x"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "x",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 19, Character: 2},
+										End:   lsproto.Position{Line: 19, Character: 2},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "lambdaThisMembers",
+			files: map[string]string{
+				mainFileName: `class Foo {
+    a: number;
+    b() {
+        var x = () => {
+            this./**/;
+        }
+    }
+}`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: []*lsproto.CompletionItem{
+						{
+							Label:            "a",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".a"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "a",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 4, Character: 17},
+										End:   lsproto.Position{Line: 4, Character: 17},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 4, Character: 17},
+										End:   lsproto.Position{Line: 4, Character: 17},
+									},
+								},
+							},
+						},
+						{
+							Label:            "b",
+							Kind:             methodKind,
+							SortText:         sortTextLocationPriority,
+							FilterText:       ptrTo(".b"),
+							InsertTextFormat: insertTextFormatPlainText,
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+									NewText: "b",
+									Insert: lsproto.Range{
+										Start: lsproto.Position{Line: 4, Character: 17},
+										End:   lsproto.Position{Line: 4, Character: 17},
+									},
+									Replace: lsproto.Range{
+										Start: lsproto.Position{Line: 4, Character: 17},
+										End:   lsproto.Position{Line: 4, Character: 17},
+									},
+								},
+							},
+						},
 					},
 				},
 			},
 		},
+		{
+			name: "memberCompletionInForEach1",
+			files: map[string]string{
+				mainFileName: `var x: string[] = [];
+x.forEach(function (y) { y./*1*/`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"1": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: core.Map(stringMembers, func(basicItem *lsproto.CompletionItem) *lsproto.CompletionItem {
+						item := *basicItem
+						item.FilterText = ptrTo("." + item.Label)
+						item.TextEdit = &lsproto.TextEditOrInsertReplaceEdit{
+							InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+								NewText: item.Label,
+								Insert: lsproto.Range{
+									Start: lsproto.Position{Line: 1, Character: 27},
+									End:   lsproto.Position{Line: 1, Character: 27},
+								},
+								Replace: lsproto.Range{
+									Start: lsproto.Position{Line: 1, Character: 27},
+									End:   lsproto.Position{Line: 1, Character: 27},
+								},
+							},
+						}
+						return &item
+					}),
+				},
+			},
+		},
+		{
+			name: "completionsTuple",
+			files: map[string]string{
+				mainFileName: `declare const x: [number, number];
+x./**/;`,
+			},
+			expected: map[string]*lsproto.CompletionList{
+				"": {
+					IsIncomplete: false,
+					ItemDefaults: itemDefaults,
+					Items: append([]*lsproto.CompletionItem{
+						{
+							Label:            "0",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							InsertText:       ptrTo("[0]"),
+							InsertTextFormat: insertTextFormatPlainText,
+							FilterText:       ptrTo(".[0]"),
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								TextEdit: &lsproto.TextEdit{
+									NewText: "[0]",
+									Range: lsproto.Range{
+										Start: lsproto.Position{Line: 1, Character: 1},
+										End:   lsproto.Position{Line: 1, Character: 2},
+									},
+								},
+							},
+						},
+						{
+							Label:            "1",
+							Kind:             fieldKind,
+							SortText:         sortTextLocationPriority,
+							InsertText:       ptrTo("[1]"),
+							InsertTextFormat: insertTextFormatPlainText,
+							FilterText:       ptrTo(".[1]"),
+							TextEdit: &lsproto.TextEditOrInsertReplaceEdit{
+								TextEdit: &lsproto.TextEdit{
+									NewText: "[1]",
+									Range: lsproto.Range{
+										Start: lsproto.Position{Line: 1, Character: 1},
+										End:   lsproto.Position{Line: 1, Character: 2},
+									},
+								},
+							},
+						},
+					}, core.Map(arrayMembers, func(basicItem *lsproto.CompletionItem) *lsproto.CompletionItem {
+						item := *basicItem
+						item.FilterText = ptrTo("." + item.Label)
+						item.TextEdit = &lsproto.TextEditOrInsertReplaceEdit{
+							InsertReplaceEdit: &lsproto.InsertReplaceEdit{
+								NewText: item.Label,
+								Insert: lsproto.Range{
+									Start: lsproto.Position{Line: 1, Character: 2},
+									End:   lsproto.Position{Line: 1, Character: 2},
+								},
+								Replace: lsproto.Range{
+									Start: lsproto.Position{Line: 1, Character: 2},
+									End:   lsproto.Position{Line: 1, Character: 2},
+								},
+							},
+						}
+						return &item
+					})...),
+				},
+			},
+		},
 	}
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			t.Parallel()
-			runTest(t, testCase.content, testCase.position, testCase.expected)
+			runTest(t, testCase.files, testCase.expected)
 		})
 	}
 }
 
-func runTest(t *testing.T, content string, position int, expected *lsproto.CompletionList) {
-	files := map[string]string{
-		"/index.ts": content,
+func runTest(t *testing.T, files map[string]string, expected map[string]*lsproto.CompletionList) {
+	parsedFiles := make(map[string]string)
+	var markerPositions map[string]*lstestutil.Marker
+	for fileName, content := range files {
+		if fileName == mainFileName {
+			testData := lstestutil.ParseTestData("", content, fileName)
+			markerPositions = testData.MarkerPositions
+			parsedFiles[fileName] = testData.Files[0].Content // !!! Assumes no usage of @filename
+		} else {
+			parsedFiles[fileName] = content
+		}
 	}
-	languageService := createLanguageService("/index.ts", files)
+	languageService := createLanguageService(mainFileName, parsedFiles)
 	context := &lsproto.CompletionContext{
 		TriggerKind: lsproto.CompletionTriggerKindInvoked,
 	}
+	ptrTrue := ptrTo(true)
 	capabilities := &lsproto.CompletionClientCapabilities{
 		CompletionItem: &lsproto.ClientCompletionItemOptions{
-			SnippetSupport:          ptrTo(true),
-			CommitCharactersSupport: ptrTo(true),
-			PreselectSupport:        ptrTo(true),
-			LabelDetailsSupport:     ptrTo(true),
+			SnippetSupport:          ptrTrue,
+			CommitCharactersSupport: ptrTrue,
+			PreselectSupport:        ptrTrue,
+			LabelDetailsSupport:     ptrTrue,
+			InsertReplaceSupport:    ptrTrue,
 		},
 		CompletionList: &lsproto.CompletionListCapabilities{
 			ItemDefaults: &[]string{"commitCharacters"},
 		},
 	}
 	preferences := &ls.UserPreferences{}
-	completionList := languageService.ProvideCompletion(
-		"/index.ts",
-		position,
-		context,
-		capabilities,
-		preferences)
-	assert.DeepEqual(t, completionList, expected)
+
+	for markerName, expectedResult := range expected {
+		marker, ok := markerPositions[markerName]
+		if !ok {
+			t.Fatalf("No marker found for '%s'", markerName)
+		}
+		completionList := languageService.ProvideCompletion(
+			"/index.ts",
+			marker.Position,
+			context,
+			capabilities,
+			preferences)
+		assert.DeepEqual(t, completionList, expectedResult)
+	}
 }
 
 func createLanguageService(fileName string, files map[string]string) *ls.LanguageService {
diff --git a/internal/ls/languageservice.go b/internal/ls/languageservice.go
index 60f0b830a1..2fc19e4549 100644
--- a/internal/ls/languageservice.go
+++ b/internal/ls/languageservice.go
@@ -66,7 +66,7 @@ func (l *LanguageService) tryGetProgramAndFile(fileName string) (*compiler.Progr
 func (l *LanguageService) getProgramAndFile(fileName string) (*compiler.Program, *ast.SourceFile) {
 	program, file := l.tryGetProgramAndFile(fileName)
 	if file == nil {
-		panic("file not found")
+		panic("file not found: " + fileName)
 	}
 	return program, file
 }
diff --git a/internal/ls/utilities.go b/internal/ls/utilities.go
index 6c642513a3..719588ae09 100644
--- a/internal/ls/utilities.go
+++ b/internal/ls/utilities.go
@@ -82,23 +82,73 @@ func assertHasRealPosition(node *ast.Node) {
 	}
 }
 
-// !!!
-func findChildOfKind(node *ast.Node, kind ast.Kind, sourceFile *ast.SourceFile) *ast.Node {
+func findChildOfKind(containingNode *ast.Node, kind ast.Kind, sourceFile *ast.SourceFile) *ast.Node {
+	lastNodePos := containingNode.Pos()
+	scanner := scanner.GetScannerForSourceFile(sourceFile, lastNodePos)
+
+	var foundChild *ast.Node
+	visitNode := func(node *ast.Node) bool {
+		if node == nil || node.Flags&ast.NodeFlagsReparsed != 0 {
+			return false
+		}
+		// Look for child in preceding tokens.
+		startPos := lastNodePos
+		for startPos < node.Pos() {
+			tokenKind := scanner.Token()
+			tokenFullStart := scanner.TokenFullStart()
+			tokenEnd := scanner.TokenEnd()
+			token := sourceFile.GetOrCreateToken(tokenKind, tokenFullStart, tokenEnd, containingNode)
+			if tokenKind == kind {
+				foundChild = token
+				return true
+			}
+			startPos = tokenEnd
+			scanner.Scan()
+		}
+		if node.Kind == kind {
+			foundChild = node
+			return true
+		}
+
+		lastNodePos = node.End()
+		scanner.ResetPos(lastNodePos)
+		return false
+	}
+
+	ast.ForEachChildAndJSDoc(containingNode, sourceFile, visitNode)
+
+	if foundChild != nil {
+		return foundChild
+	}
+
+	// Look for child in trailing tokens.
+	startPos := lastNodePos
+	for startPos < containingNode.End() {
+		tokenKind := scanner.Token()
+		tokenFullStart := scanner.TokenFullStart()
+		tokenEnd := scanner.TokenEnd()
+		token := sourceFile.GetOrCreateToken(tokenKind, tokenFullStart, tokenEnd, containingNode)
+		if tokenKind == kind {
+			return token
+		}
+		startPos = tokenEnd
+		scanner.Scan()
+	}
 	return nil
 }
 
-// !!!
+// !!! signature help
 type PossibleTypeArgumentInfo struct {
 	called         *ast.IdentifierNode
 	nTypeArguments int
 }
 
-// !!!
+// !!! signature help
 func getPossibleTypeArgumentsInfo(tokenIn *ast.Node, sourceFile *ast.SourceFile) *PossibleTypeArgumentInfo {
 	return nil
 }
 
-// !!!
+// !!! signature help
 func getPossibleGenericSignatures(called *ast.Expression, typeArgumentCount int, checker *checker.Checker) []*checker.Signature {
 	return nil
 }
diff --git a/internal/testutil/lstestutil/lstestutil.go b/internal/testutil/lstestutil/lstestutil.go
new file mode 100644
index 0000000000..fc81641246
--- /dev/null
+++ b/internal/testutil/lstestutil/lstestutil.go
@@ -0,0 +1,187 @@
+package lstestutil
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/microsoft/typescript-go/internal/core"
+)
+
+type markerRange struct {
+	core.TextRange
+	filename string
+	position int
+	data     string
+}
+
+type Marker struct {
+	Filename string
+	Position int
+	Name     string
+}
+
+type TestData struct {
+	Files           []*TestFileInfo
+	MarkerPositions map[string]*Marker
+	//markers         []*Marker
+	/**
+	 * Inserted in source files by surrounding desired text
+	 * in a range with `[|` and `|]`. For example,
+	 *
+	 * [|text in range|]
+	 *
+	 * is a range with `text in range` "selected".
+	 */
+	Ranges markerRange
+}
+
+func ParseTestData(basePath string, contents string, fileName string) TestData {
+	// List of all the subfiles we've parsed out
+	var files []*TestFileInfo
+
+	// Split up the input file by line
+	lines := strings.Split(contents, "\n")
+	currentFileContent := ""
+
+	for _, line := range lines {
+		if len(line) > 0 && line[len(line)-1] == '\r' {
+			line = line[:len(line)-1]
+		}
+		if currentFileContent == "" {
+			currentFileContent = line
+		} else {
+			currentFileContent += "\n" + line
+		}
+	}
+
+	if currentFileContent == "" {
+		return TestData{}
+	}
+	markerPositions := make(map[string]*Marker)
+	markers := []*Marker{}
+
+	// If we have multiple files, then parseFileContent needs to be called for each file.
+	// This will be achieved by creating a `nextFile()` func that will call `parseFileContent()` for each file.
+	testFileInfo := parseFileContent(currentFileContent, fileName, markerPositions, &markers)
+	files = append(files, testFileInfo)
+
+	return TestData{
+		Files:           files,
+		MarkerPositions: markerPositions,
+		// markers:         markers,
+		Ranges: markerRange{},
+	}
+}
+
+type locationInformation struct {
+	position       int
+	sourcePosition int
+	sourceLine     int
+	sourceColumn   int
+}
+
+type TestFileInfo struct { // for FourSlashFile
+	Filename string
+	// The contents of the file (with markers, etc stripped out)
+	Content string
+}
+
+func parseFileContent(content string, filename string, markerMap map[string]*Marker, markers *[]*Marker) *TestFileInfo {
+	// !!! chompLeadingSpace
+	// !!! validate characters in markers
+	// Any slash-star comment with a character not in this string is not a marker.
+	// const validMarkerChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz$1234567890_"
+
+	/// The file content (minus metacharacters) so far
+	output := ""
+
+	/// The total number of metacharacters removed from the file (so far)
+	difference := 0
+
+	/// Current position data
+	line := 1
+	column := 1
+
+	/// The current marker (or maybe multi-line comment?) we're parsing, possibly
+	var openMarker locationInformation
+
+	/// The latest position of the start of an unflushed plain text area
+	lastNormalCharPosition := 0
+
+	flush := func(lastSafeCharIndex int) {
+		if lastSafeCharIndex != -1 {
+			output = output + content[lastNormalCharPosition:lastSafeCharIndex]
+		} else {
+			output = output + content[lastNormalCharPosition:]
+		}
+	}
+
+	previousCharacter := content[0]
+	for i := 1; i < len(content); i++ {
+		currentCharacter := content[i]
+		if previousCharacter == '/' && currentCharacter == '*' {
+			// found a possible marker start
+			openMarker = locationInformation{
+				position:       (i - 1) - difference,
+				sourcePosition: i - 1,
+				sourceLine:     line,
+				sourceColumn:   column,
+			}
+		}
+		if previousCharacter == '*' && currentCharacter == '/' {
+			// Record the marker
+			// start + 2 to ignore the */, -1 on the end to ignore the * (/ is next)
+			markerNameText := strings.TrimSpace(content[openMarker.sourcePosition+2 : i-1])
+			recordMarker(filename, openMarker, markerNameText, markerMap, markers)
+
+			flush(openMarker.sourcePosition)
+			lastNormalCharPosition = i + 1
+			difference += i + 1 - openMarker.sourcePosition
+
+			// Set the current start to point to the end of the current marker to ignore its text
+			openMarker = locationInformation{}
+		}
+		if currentCharacter == '\n' && previousCharacter == '\r' {
+			// Ignore trailing \n after \r
+			continue
+		} else if currentCharacter == '\n' || currentCharacter == '\r' {
+			line++
+			column = 1
+			continue
+		}
+
+		column++
+		previousCharacter = currentCharacter
+	}
+
+	// Add the remaining text
+	flush(-1)
+
+	return &TestFileInfo{
+		Content:  output,
+		Filename: filename,
+	}
+}
+
+func recordMarker(
+	filename string,
+	location locationInformation,
+	name string,
+	markerMap map[string]*Marker,
+	markers *[]*Marker,
+) *Marker {
+	// Record the marker
+	marker := &Marker{
+		Filename: filename,
+		Position: location.position,
+		Name:     name,
+	}
+	// Verify markers for uniqueness
+	if _, ok := markerMap[name]; ok {
+		fmt.Printf("Duplicate marker name: %s\n", name) // tbd print error msg
+	} else {
+		markerMap[name] = marker
+		(*markers) = append(*markers, marker)
+	}
+	return marker
+}