fix parsing string union indexers (#1750)

Today this code results in a syntax error: `type foo = { ["bar" |
"baz"]: number }`. This is odd and I believe it is a bug. I have fixed
this so that it is now parsed as an indexer field with a union type.
This change should not affect the way any code is parsed today, and
allow types in indexers to begin with string literals.

---------

Co-authored-by: ariel <aweiss@hey.com>

Ast/include/Luau/Parser.h

@@ -228,9 +228,9 @@ private:
         Position colonPosition;
     };
 
-    TableIndexerResult parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation);
+    TableIndexerResult parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin);
     // Remove with FFlagLuauStoreCSTData
-    AstTableIndexer* parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation);
+    AstTableIndexer* parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin);
 
     AstTypeOrPack parseFunctionType(bool allowPack, const AstArray<AstAttr*>& attributes);
     AstType* parseFunctionTypeTail(

Ast/src/Parser.cpp

@@ -28,6 +28,7 @@ LUAU_FASTFLAGVARIABLE(LuauAstTypeGroup3)
 LUAU_FASTFLAGVARIABLE(ParserNoErrorLimit)
 LUAU_FASTFLAGVARIABLE(LuauFixDoBlockEndLocation)
 LUAU_FASTFLAGVARIABLE(LuauParseOptionalAsNode)
+LUAU_FASTFLAGVARIABLE(LuauParseStringIndexer)
 
 namespace Luau
 {
@@ -1260,75 +1261,158 @@ AstStat* Parser::parseDeclaration(const Location& start, const AstArray<AstAttr*
 
         while (lexer.current().type != Lexeme::ReservedEnd)
         {
-            // There are two possibilities: Either it's a property or a function.
-            if (lexer.current().type == Lexeme::ReservedFunction)
+            if (FFlag::LuauParseStringIndexer)
             {
-                props.push_back(parseDeclaredClassMethod());
-            }
-            else if (lexer.current().type == '[' && (lexer.lookahead().type == Lexeme::RawString || lexer.lookahead().type == Lexeme::QuotedString))
-            {
-                const Lexeme begin = lexer.current();
-                nextLexeme(); // [
-
-                const Location nameBegin = lexer.current().location;
-                std::optional<AstArray<char>> chars = parseCharArray();
-
-                const Location nameEnd = lexer.previousLocation();
-
-                expectMatchAndConsume(']', begin);
-                expectAndConsume(':', "property type annotation");
-                AstType* type = parseType();
-
-                // since AstName contains a char*, it can't contain null
-                bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
-
-                if (chars && !containsNull)
+                // There are two possibilities: Either it's a property or a function.
+                if (lexer.current().type == Lexeme::ReservedFunction)
                 {
-                    props.push_back(AstDeclaredClassProp{
-                        AstName(chars->data), Location(nameBegin, nameEnd), type, false, Location(begin.location, lexer.previousLocation())
-                    });
+                    props.push_back(parseDeclaredClassMethod());
+                }
+                else if (lexer.current().type == '[')
+                {
+                    const Lexeme begin = lexer.current();
+                    nextLexeme(); // [
+
+                    if ((lexer.current().type == Lexeme::RawString || lexer.current().type == Lexeme::QuotedString) && lexer.lookahead().type == ']')
+                    {
+                        const Location nameBegin = lexer.current().location;
+                        std::optional<AstArray<char>> chars = parseCharArray();
+        
+                        const Location nameEnd = lexer.previousLocation();
+        
+                        expectMatchAndConsume(']', begin);
+                        expectAndConsume(':', "property type annotation");
+                        AstType* type = parseType();
+        
+                        // since AstName contains a char*, it can't contain null
+                        bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
+        
+                        if (chars && !containsNull)
+                        {
+                            props.push_back(AstDeclaredClassProp{
+                                AstName(chars->data), Location(nameBegin, nameEnd), type, false, Location(begin.location, lexer.previousLocation())
+                            });
+                        }
+                        else
+                        {
+                            report(begin.location, "String literal contains malformed escape sequence or \\0");
+                        }
+                    }
+                    else
+                    {
+                        if (indexer)
+                        {
+                            // maybe we don't need to parse the entire badIndexer...
+                            // however, we either have { or [ to lint, not the entire table type or the bad indexer.
+                            AstTableIndexer* badIndexer;
+                            if (FFlag::LuauStoreCSTData)
+                                badIndexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt, begin).node;
+                            else
+                                badIndexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt, begin);
+        
+                            // we lose all additional indexer expressions from the AST after error recovery here
+                            report(badIndexer->location, "Cannot have more than one class indexer");
+                        }
+                        else
+                        {
+                            if (FFlag::LuauStoreCSTData)
+                                indexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt, begin).node;
+                            else
+                                indexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt, begin);
+                        }
+                    }
                 }
                 else
                 {
-                    report(begin.location, "String literal contains malformed escape sequence or \\0");
-                }
-            }
-            else if (lexer.current().type == '[')
-            {
-                if (indexer)
-                {
-                    // maybe we don't need to parse the entire badIndexer...
-                    // however, we either have { or [ to lint, not the entire table type or the bad indexer.
-                    AstTableIndexer* badIndexer;
-                    if (FFlag::LuauStoreCSTData)
-                        badIndexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt).node;
-                    else
-                        badIndexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt);
+                    Location propStart = lexer.current().location;
+                    std::optional<Name> propName = parseNameOpt("property name");
 
-                    // we lose all additional indexer expressions from the AST after error recovery here
-                    report(badIndexer->location, "Cannot have more than one class indexer");
-                }
-                else
-                {
-                    if (FFlag::LuauStoreCSTData)
-                        indexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt).node;
-                    else
-                        indexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt);
+                    if (!propName)
+                        break;
+
+                    expectAndConsume(':', "property type annotation");
+                    AstType* propType = parseType();
+                    props.push_back(
+                        AstDeclaredClassProp{propName->name, propName->location, propType, false, Location(propStart, lexer.previousLocation())}
+                    );
                 }
             }
             else
             {
-                Location propStart = lexer.current().location;
-                std::optional<Name> propName = parseNameOpt("property name");
+                // There are two possibilities: Either it's a property or a function.
+                if (lexer.current().type == Lexeme::ReservedFunction)
+                {
+                    props.push_back(parseDeclaredClassMethod());
+                }
+                else if (lexer.current().type == '[' && (lexer.lookahead().type == Lexeme::RawString || lexer.lookahead().type == Lexeme::QuotedString))
+                {
+                    const Lexeme begin = lexer.current();
+                    nextLexeme(); // [
 
-                if (!propName)
-                    break;
+                    const Location nameBegin = lexer.current().location;
+                    std::optional<AstArray<char>> chars = parseCharArray();
 
-                expectAndConsume(':', "property type annotation");
-                AstType* propType = parseType();
-                props.push_back(
-                    AstDeclaredClassProp{propName->name, propName->location, propType, false, Location(propStart, lexer.previousLocation())}
-                );
+                    const Location nameEnd = lexer.previousLocation();
+
+                    expectMatchAndConsume(']', begin);
+                    expectAndConsume(':', "property type annotation");
+                    AstType* type = parseType();
+
+                    // since AstName contains a char*, it can't contain null
+                    bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
+
+                    if (chars && !containsNull)
+                    {
+                        props.push_back(AstDeclaredClassProp{
+                            AstName(chars->data), Location(nameBegin, nameEnd), type, false, Location(begin.location, lexer.previousLocation())
+                        });
+                    }
+                    else
+                    {
+                        report(begin.location, "String literal contains malformed escape sequence or \\0");
+                    }
+                }
+                else if (lexer.current().type == '[')
+                {
+                    if (indexer)
+                    {
+                        // maybe we don't need to parse the entire badIndexer...
+                        // however, we either have { or [ to lint, not the entire table type or the bad indexer.
+                        AstTableIndexer* badIndexer;
+                        if (FFlag::LuauStoreCSTData)
+                            // the last param in the parseTableIndexer is ignored since FFlagLuauParseStringIndexer is false here
+                            badIndexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt, lexer.current()).node;
+                        else
+                            // the last param in the parseTableIndexer is ignored since FFlagLuauParseStringIndexer is false here
+                            badIndexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt, lexer.current());
+
+                        // we lose all additional indexer expressions from the AST after error recovery here
+                        report(badIndexer->location, "Cannot have more than one class indexer");
+                    }
+                    else
+                    {
+                        if (FFlag::LuauStoreCSTData)
+                            // the last param in the parseTableIndexer is ignored since FFlagLuauParseStringIndexer is false here
+                            indexer = parseTableIndexer(AstTableAccess::ReadWrite, std::nullopt, lexer.current()).node;
+                        else
+                            // the last param in the parseTableIndexer is ignored since FFlagLuauParseStringIndexer is false here
+                            indexer = parseTableIndexer_DEPRECATED(AstTableAccess::ReadWrite, std::nullopt, lexer.current());
+                    }
+                }
+                else
+                {
+                    Location propStart = lexer.current().location;
+                    std::optional<Name> propName = parseNameOpt("property name");
+
+                    if (!propName)
+                        break;
+
+                    expectAndConsume(':', "property type annotation");
+                    AstType* propType = parseType();
+                    props.push_back(
+                        AstDeclaredClassProp{propName->name, propName->location, propType, false, Location(propStart, lexer.previousLocation())}
+                    );
+                }
             }
         }
 
@@ -1861,10 +1945,13 @@ std::pair<CstExprConstantString::QuoteStyle, unsigned int> Parser::extractString
 }
 
 // TableIndexer ::= `[' Type `]' `:' Type
-Parser::TableIndexerResult Parser::parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation)
+Parser::TableIndexerResult Parser::parseTableIndexer(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin)
 {
-    const Lexeme begin = lexer.current();
-    nextLexeme(); // [
+    if (!FFlag::LuauParseStringIndexer)
+    {
+        begin = lexer.current();
+        nextLexeme(); // [
+    }
 
     AstType* index = parseType();
 
@@ -1885,10 +1972,13 @@ Parser::TableIndexerResult Parser::parseTableIndexer(AstTableAccess access, std:
 }
 
 // Remove with FFlagLuauStoreCSTData
-AstTableIndexer* Parser::parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation)
+AstTableIndexer* Parser::parseTableIndexer_DEPRECATED(AstTableAccess access, std::optional<Location> accessLocation, Lexeme begin)
 {
-    const Lexeme begin = lexer.current();
-    nextLexeme(); // [
+    if (!FFlag::LuauParseStringIndexer)
+    {
+        begin = lexer.current();
+        nextLexeme(); // [
+    }
 
     AstType* index = parseType();
 
@@ -1941,116 +2031,240 @@ AstType* Parser::parseTableType(bool inDeclarationContext)
             }
         }
 
-        if (lexer.current().type == '[' && (lexer.lookahead().type == Lexeme::RawString || lexer.lookahead().type == Lexeme::QuotedString))
+        if (FFlag::LuauParseStringIndexer)
         {
-            const Lexeme begin = lexer.current();
-            nextLexeme(); // [
-
-            CstExprConstantString::QuoteStyle style;
-            unsigned int blockDepth = 0;
-            if (FFlag::LuauStoreCSTData && options.storeCstData)
-                std::tie(style, blockDepth) = extractStringDetails();
-
-            AstArray<char> sourceString;
-            std::optional<AstArray<char>> chars = parseCharArray(options.storeCstData ? &sourceString : nullptr);
-
-            Position indexerClosePosition = lexer.current().location.begin;
-            expectMatchAndConsume(']', begin);
-            Position colonPosition = lexer.current().location.begin;
-            expectAndConsume(':', "table field");
-
-            AstType* type = parseType();
-
-            // since AstName contains a char*, it can't contain null
-            bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
-
-            if (chars && !containsNull)
+            if (lexer.current().type == '[')
             {
-                props.push_back(AstTableProp{AstName(chars->data), begin.location, type, access, accessLocation});
+                const Lexeme begin = lexer.current();
+                nextLexeme(); // [
+    
+                if ((lexer.current().type == Lexeme::RawString || lexer.current().type == Lexeme::QuotedString) && lexer.lookahead().type == ']')
+                {
+                    CstExprConstantString::QuoteStyle style;
+                    unsigned int blockDepth = 0;
+                    if (FFlag::LuauStoreCSTData && options.storeCstData)
+                        std::tie(style, blockDepth) = extractStringDetails();
+        
+                    AstArray<char> sourceString;
+                    std::optional<AstArray<char>> chars = parseCharArray(options.storeCstData ? &sourceString : nullptr);
+        
+                    Position indexerClosePosition = lexer.current().location.begin;
+                    expectMatchAndConsume(']', begin);
+                    Position colonPosition = lexer.current().location.begin;
+                    expectAndConsume(':', "table field");
+        
+                    AstType* type = parseType();
+        
+                    // since AstName contains a char*, it can't contain null
+                    bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
+        
+                    if (chars && !containsNull)
+                    {
+                        props.push_back(AstTableProp{AstName(chars->data), begin.location, type, access, accessLocation});
+                        if (FFlag::LuauStoreCSTData && options.storeCstData)
+                            cstItems.push_back(CstTypeTable::Item{
+                                CstTypeTable::Item::Kind::StringProperty,
+                                begin.location.begin,
+                                indexerClosePosition,
+                                colonPosition,
+                                tableSeparator(),
+                                lexer.current().location.begin,
+                                allocator.alloc<CstExprConstantString>(sourceString, style, blockDepth)
+                            });
+                    }
+                    else
+                        report(begin.location, "String literal contains malformed escape sequence or \\0");
+                }
+                else
+                {
+                    if (indexer)
+                    {
+                        // maybe we don't need to parse the entire badIndexer...
+                        // however, we either have { or [ to lint, not the entire table type or the bad indexer.
+                        AstTableIndexer* badIndexer;
+                        if (FFlag::LuauStoreCSTData)
+                            badIndexer = parseTableIndexer(access, accessLocation, begin).node;
+                        else
+                            badIndexer = parseTableIndexer_DEPRECATED(access, accessLocation, begin);
+        
+                        // we lose all additional indexer expressions from the AST after error recovery here
+                        report(badIndexer->location, "Cannot have more than one table indexer");
+                    }
+                    else
+                    {
+                        if (FFlag::LuauStoreCSTData)
+                        {
+                            auto tableIndexerResult = parseTableIndexer(access, accessLocation, begin);
+                            indexer = tableIndexerResult.node;
+                            if (options.storeCstData)
+                                cstItems.push_back(CstTypeTable::Item{
+                                    CstTypeTable::Item::Kind::Indexer,
+                                    tableIndexerResult.indexerOpenPosition,
+                                    tableIndexerResult.indexerClosePosition,
+                                    tableIndexerResult.colonPosition,
+                                    tableSeparator(),
+                                    lexer.current().location.begin,
+                                });
+                        }
+                        else
+                        {
+                            indexer = parseTableIndexer_DEPRECATED(access, accessLocation, begin);
+                        }
+                    }
+                }
+            }
+            else if (props.empty() && !indexer && !(lexer.current().type == Lexeme::Name && lexer.lookahead().type == ':'))
+            {
+                AstType* type = parseType();
+
+                // array-like table type: {T} desugars into {[number]: T}
+                isArray = true;
+                AstType* index = allocator.alloc<AstTypeReference>(type->location, std::nullopt, nameNumber, std::nullopt, type->location);
+                indexer = allocator.alloc<AstTableIndexer>(AstTableIndexer{index, type, type->location, access, accessLocation});
+
+                break;
+            }
+            else
+            {
+                std::optional<Name> name = parseNameOpt("table field");
+
+                if (!name)
+                    break;
+
+                Position colonPosition = lexer.current().location.begin;
+                expectAndConsume(':', "table field");
+
+                AstType* type = parseType(inDeclarationContext);
+
+                props.push_back(AstTableProp{name->name, name->location, type, access, accessLocation});
                 if (FFlag::LuauStoreCSTData && options.storeCstData)
                     cstItems.push_back(CstTypeTable::Item{
-                        CstTypeTable::Item::Kind::StringProperty,
-                        begin.location.begin,
-                        indexerClosePosition,
+                        CstTypeTable::Item::Kind::Property,
+                        Position{0, 0},
+                        Position{0, 0},
                         colonPosition,
                         tableSeparator(),
-                        lexer.current().location.begin,
-                        allocator.alloc<CstExprConstantString>(sourceString, style, blockDepth)
+                        lexer.current().location.begin
                     });
             }
-            else
-                report(begin.location, "String literal contains malformed escape sequence or \\0");
-        }
-        else if (lexer.current().type == '[')
-        {
-            if (indexer)
-            {
-                // maybe we don't need to parse the entire badIndexer...
-                // however, we either have { or [ to lint, not the entire table type or the bad indexer.
-                AstTableIndexer* badIndexer;
-                if (FFlag::LuauStoreCSTData)
-                    badIndexer = parseTableIndexer(access, accessLocation).node;
-                else
-                    badIndexer = parseTableIndexer_DEPRECATED(access, accessLocation);
-
-                // we lose all additional indexer expressions from the AST after error recovery here
-                report(badIndexer->location, "Cannot have more than one table indexer");
-            }
-            else
-            {
-                if (FFlag::LuauStoreCSTData)
-                {
-                    auto tableIndexerResult = parseTableIndexer(access, accessLocation);
-                    indexer = tableIndexerResult.node;
-                    if (options.storeCstData)
-                        cstItems.push_back(CstTypeTable::Item{
-                            CstTypeTable::Item::Kind::Indexer,
-                            tableIndexerResult.indexerOpenPosition,
-                            tableIndexerResult.indexerClosePosition,
-                            tableIndexerResult.colonPosition,
-                            tableSeparator(),
-                            lexer.current().location.begin,
-                        });
-                }
-                else
-                {
-                    indexer = parseTableIndexer_DEPRECATED(access, accessLocation);
-                }
-            }
-        }
-        else if (props.empty() && !indexer && !(lexer.current().type == Lexeme::Name && lexer.lookahead().type == ':'))
-        {
-            AstType* type = parseType();
-
-            // array-like table type: {T} desugars into {[number]: T}
-            isArray = true;
-            AstType* index = allocator.alloc<AstTypeReference>(type->location, std::nullopt, nameNumber, std::nullopt, type->location);
-            indexer = allocator.alloc<AstTableIndexer>(AstTableIndexer{index, type, type->location, access, accessLocation});
-
-            break;
         }
         else
         {
-            std::optional<Name> name = parseNameOpt("table field");
+            if (lexer.current().type == '[' && (lexer.lookahead().type == Lexeme::RawString || lexer.lookahead().type == Lexeme::QuotedString))
+            {
+                const Lexeme begin = lexer.current();
+                nextLexeme(); // [
+
+                CstExprConstantString::QuoteStyle style;
+                unsigned int blockDepth = 0;
+                if (FFlag::LuauStoreCSTData && options.storeCstData)
+                    std::tie(style, blockDepth) = extractStringDetails();
+
+                AstArray<char> sourceString;
+                std::optional<AstArray<char>> chars = parseCharArray(options.storeCstData ? &sourceString : nullptr);
+
+                Position indexerClosePosition = lexer.current().location.begin;
+                expectMatchAndConsume(']', begin);
+                Position colonPosition = lexer.current().location.begin;
+                expectAndConsume(':', "table field");
+
+                AstType* type = parseType();
+
+                // since AstName contains a char*, it can't contain null
+                bool containsNull = chars && (memchr(chars->data, 0, chars->size) != nullptr);
+
+                if (chars && !containsNull)
+                {
+                    props.push_back(AstTableProp{AstName(chars->data), begin.location, type, access, accessLocation});
+                    if (FFlag::LuauStoreCSTData && options.storeCstData)
+                        cstItems.push_back(CstTypeTable::Item{
+                            CstTypeTable::Item::Kind::StringProperty,
+                            begin.location.begin,
+                            indexerClosePosition,
+                            colonPosition,
+                            tableSeparator(),
+                            lexer.current().location.begin,
+                            allocator.alloc<CstExprConstantString>(sourceString, style, blockDepth)
+                        });
+                }
+                else
+                    report(begin.location, "String literal contains malformed escape sequence or \\0");
+            }
+            else if (lexer.current().type == '[')
+            {
+                if (indexer)
+                {
+                    // maybe we don't need to parse the entire badIndexer...
+                    // however, we either have { or [ to lint, not the entire table type or the bad indexer.
+                    AstTableIndexer* badIndexer;
+                    if (FFlag::LuauStoreCSTData)
+                        // the last param in the parseTableIndexer is ignored
+                        badIndexer = parseTableIndexer(access, accessLocation, lexer.current()).node;
+                    else
+                        // the last param in the parseTableIndexer is ignored
+                        badIndexer = parseTableIndexer_DEPRECATED(access, accessLocation, lexer.current());
+
+                    // we lose all additional indexer expressions from the AST after error recovery here
+                    report(badIndexer->location, "Cannot have more than one table indexer");
+                }
+                else
+                {
+                    if (FFlag::LuauStoreCSTData)
+                    {
+                        // the last param in the parseTableIndexer is ignored
+                        auto tableIndexerResult = parseTableIndexer(access, accessLocation, lexer.current());
+                        indexer = tableIndexerResult.node;
+                        if (options.storeCstData)
+                            cstItems.push_back(CstTypeTable::Item{
+                                CstTypeTable::Item::Kind::Indexer,
+                                tableIndexerResult.indexerOpenPosition,
+                                tableIndexerResult.indexerClosePosition,
+                                tableIndexerResult.colonPosition,
+                                tableSeparator(),
+                                lexer.current().location.begin,
+                            });
+                    }
+                    else
+                    {
+                        // the last param in the parseTableIndexer is ignored
+                        indexer = parseTableIndexer_DEPRECATED(access, accessLocation, lexer.current());
+                    }
+                }
+            }
+            else if (props.empty() && !indexer && !(lexer.current().type == Lexeme::Name && lexer.lookahead().type == ':'))
+            {
+                AstType* type = parseType();
+
+                // array-like table type: {T} desugars into {[number]: T}
+                isArray = true;
+                AstType* index = allocator.alloc<AstTypeReference>(type->location, std::nullopt, nameNumber, std::nullopt, type->location);
+                indexer = allocator.alloc<AstTableIndexer>(AstTableIndexer{index, type, type->location, access, accessLocation});
 
-            if (!name)
                 break;
+            }
+            else
+            {
+                std::optional<Name> name = parseNameOpt("table field");
 
-            Position colonPosition = lexer.current().location.begin;
-            expectAndConsume(':', "table field");
+                if (!name)
+                    break;
 
-            AstType* type = parseType(inDeclarationContext);
+                Position colonPosition = lexer.current().location.begin;
+                expectAndConsume(':', "table field");
 
-            props.push_back(AstTableProp{name->name, name->location, type, access, accessLocation});
-            if (FFlag::LuauStoreCSTData && options.storeCstData)
-                cstItems.push_back(CstTypeTable::Item{
-                    CstTypeTable::Item::Kind::Property,
-                    Position{0, 0},
-                    Position{0, 0},
-                    colonPosition,
-                    tableSeparator(),
-                    lexer.current().location.begin
-                });
+                AstType* type = parseType(inDeclarationContext);
+
+                props.push_back(AstTableProp{name->name, name->location, type, access, accessLocation});
+                if (FFlag::LuauStoreCSTData && options.storeCstData)
+                    cstItems.push_back(CstTypeTable::Item{
+                        CstTypeTable::Item::Kind::Property,
+                        Position{0, 0},
+                        Position{0, 0},
+                        colonPosition,
+                        tableSeparator(),
+                        lexer.current().location.begin
+                    });
+            }
         }
 
         if (lexer.current().type == ',' || lexer.current().type == ';')

tests/Parser.test.cpp

@@ -24,6 +24,7 @@ LUAU_FASTFLAG(LuauPreserveUnionIntersectionNodeForLeadingTokenSingleType)
 LUAU_FASTFLAG(LuauAstTypeGroup3)
 LUAU_FASTFLAG(LuauFixDoBlockEndLocation)
 LUAU_FASTFLAG(LuauParseOptionalAsNode)
+LUAU_FASTFLAG(LuauParseStringIndexer)
 
 namespace
 {
@@ -3938,5 +3939,10 @@ TEST_CASE_FIXTURE(Fixture, "parsing_type_suffix_for_return_type_with_variadic")
     CHECK(result.errors.size() == 0);
 }
 
+TEST_CASE_FIXTURE(Fixture, "parsing_string_union_indexers")
+{
+    ScopedFastFlag _{FFlag::LuauParseStringIndexer, true};
+    parse(R"(type foo = { ["bar" | "baz"]: number })");
+}
 
 TEST_SUITE_END();