Add support for ClassType indexer in definition files (#949)

Analysis/src/AstJsonEncoder.cpp

@@ -752,6 +752,7 @@ struct AstJsonEncoder : public AstVisitor
             if (node->superName)
                 write("superName", *node->superName);
             PROP(props);
+            PROP(indexer);
         });
     }
 

Analysis/src/ConstraintGraphBuilder.cpp

@@ -22,6 +22,7 @@
 
 LUAU_FASTINT(LuauCheckRecursionLimit);
 LUAU_FASTFLAG(DebugLuauMagicTypes);
+LUAU_FASTFLAG(LuauParseDeclareClassIndexer);
 
 namespace Luau
 {
@@ -1157,6 +1158,23 @@ ControlFlow ConstraintGraphBuilder::visit(const ScopePtr& scope, AstStatDeclareC
 
     scope->exportedTypeBindings[className] = TypeFun{{}, classTy};
 
+    if (FFlag::LuauParseDeclareClassIndexer && declaredClass->indexer)
+    {
+        RecursionCounter counter{&recursionCount};
+
+        if (recursionCount >= FInt::LuauCheckRecursionLimit)
+        {
+            reportCodeTooComplex(declaredClass->indexer->location);
+        }
+        else
+        {
+            ctv->indexer = TableIndexer{
+                resolveType(scope, declaredClass->indexer->indexType, /* inTypeArguments */ false),
+                resolveType(scope, declaredClass->indexer->resultType, /* inTypeArguments */ false),
+            };
+        }
+    }
+
     for (const AstDeclaredClassProp& prop : declaredClass->props)
     {
         Name propName(prop.name.value);

Analysis/src/TypeAttach.cpp

@@ -13,6 +13,8 @@
 
 #include <string>
 
+LUAU_FASTFLAG(LuauParseDeclareClassIndexer);
+
 static char* allocateString(Luau::Allocator& allocator, std::string_view contents)
 {
     char* result = (char*)allocator.allocate(contents.size() + 1);
@@ -227,7 +229,17 @@ public:
             idx++;
         }
 
-        return allocator->alloc<AstTypeTable>(Location(), props);
+        AstTableIndexer* indexer = nullptr;
+        if (FFlag::LuauParseDeclareClassIndexer && ctv.indexer)
+        {
+            RecursionCounter counter(&count);
+
+            indexer = allocator->alloc<AstTableIndexer>();
+            indexer->indexType = Luau::visit(*this, ctv.indexer->indexType->ty);
+            indexer->resultType = Luau::visit(*this, ctv.indexer->indexResultType->ty);
+        }
+
+        return allocator->alloc<AstTypeTable>(Location(), props, indexer);
     }
 
     AstType* operator()(const FunctionType& ftv)

Analysis/src/TypeInfer.cpp

@@ -41,6 +41,7 @@ LUAU_FASTFLAGVARIABLE(LuauTypecheckTypeguards, false)
 LUAU_FASTFLAGVARIABLE(LuauTinyControlFlowAnalysis, false)
 LUAU_FASTFLAGVARIABLE(LuauTypecheckClassTypeIndexers, false)
 LUAU_FASTFLAGVARIABLE(LuauAlwaysCommitInferencesOfFunctionCalls, false)
+LUAU_FASTFLAG(LuauParseDeclareClassIndexer)
 
 namespace Luau
 {
@@ -1757,6 +1758,9 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatDeclareClass&
     if (!ctv->metatable)
         ice("No metatable for declared class");
 
+    if (const auto& indexer = declaredClass.indexer; FFlag::LuauParseDeclareClassIndexer && indexer)
+        ctv->indexer = TableIndexer(resolveType(scope, *indexer->indexType), resolveType(scope, *indexer->resultType));
+
     TableType* metatable = getMutable<TableType>(*ctv->metatable);
     for (const AstDeclaredClassProp& prop : declaredClass.props)
     {

Ast/include/Luau/Ast.h

@@ -801,12 +801,20 @@ struct AstDeclaredClassProp
     bool isMethod = false;
 };
 
+struct AstTableIndexer
+{
+    AstType* indexType;
+    AstType* resultType;
+    Location location;
+};
+
 class AstStatDeclareClass : public AstStat
 {
 public:
     LUAU_RTTI(AstStatDeclareClass)
 
-    AstStatDeclareClass(const Location& location, const AstName& name, std::optional<AstName> superName, const AstArray<AstDeclaredClassProp>& props);
+    AstStatDeclareClass(const Location& location, const AstName& name, std::optional<AstName> superName, const AstArray<AstDeclaredClassProp>& props,
+        AstTableIndexer* indexer = nullptr);
 
     void visit(AstVisitor* visitor) override;
 
@@ -814,6 +822,7 @@ public:
     std::optional<AstName> superName;
 
     AstArray<AstDeclaredClassProp> props;
+    AstTableIndexer* indexer;
 };
 
 class AstType : public AstNode
@@ -862,13 +871,6 @@ struct AstTableProp
     AstType* type;
 };
 
-struct AstTableIndexer
-{
-    AstType* indexType;
-    AstType* resultType;
-    Location location;
-};
-
 class AstTypeTable : public AstType
 {
 public:

Ast/src/Ast.cpp

@@ -714,12 +714,13 @@ void AstStatDeclareFunction::visit(AstVisitor* visitor)
     }
 }
 
-AstStatDeclareClass::AstStatDeclareClass(
+AstStatDeclareClass::AstStatDeclareClass(const Location& location, const AstName& name, std::optional<AstName> superName,
-    const Location& location, const AstName& name, std::optional<AstName> superName, const AstArray<AstDeclaredClassProp>& props)
+    const AstArray<AstDeclaredClassProp>& props, AstTableIndexer* indexer)
     : AstStat(ClassIndex(), location)
     , name(name)
     , superName(superName)
     , props(props)
+    , indexer(indexer)
 {
 }
 

Ast/src/Parser.cpp

@@ -13,6 +13,7 @@
 // See docs/SyntaxChanges.md for an explanation.
 LUAU_FASTINTVARIABLE(LuauRecursionLimit, 1000)
 LUAU_FASTINTVARIABLE(LuauParseErrorLimit, 100)
+LUAU_FASTFLAGVARIABLE(LuauParseDeclareClassIndexer, false)
 
 #define ERROR_INVALID_INTERP_DOUBLE_BRACE "Double braces are not permitted within interpolated strings. Did you mean '\\{'?"
 
@@ -877,6 +878,7 @@ AstStat* Parser::parseDeclaration(const Location& start)
         }
 
         TempVector<AstDeclaredClassProp> props(scratchDeclaredClassProps);
+        AstTableIndexer* indexer = nullptr;
 
         while (lexer.current().type != Lexeme::ReservedEnd)
         {
@@ -885,7 +887,8 @@ AstStat* Parser::parseDeclaration(const Location& start)
             {
                 props.push_back(parseDeclaredClassMethod());
             }
-            else if (lexer.current().type == '[')
+            else if (lexer.current().type == '[' && (!FFlag::LuauParseDeclareClassIndexer || lexer.lookahead().type == Lexeme::RawString ||
+                                                        lexer.lookahead().type == Lexeme::QuotedString))
             {
                 const Lexeme begin = lexer.current();
                 nextLexeme(); // [
@@ -904,6 +907,22 @@ AstStat* Parser::parseDeclaration(const Location& start)
                 else
                     report(begin.location, "String literal contains malformed escape sequence");
             }
+            else if (lexer.current().type == '[' && FFlag::LuauParseDeclareClassIndexer)
+            {
+                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 = parseTableIndexer();
+
+                    // we lose all additional indexer expressions from the AST after error recovery here
+                    report(badIndexer->location, "Cannot have more than one class indexer");
+                }
+                else
+                {
+                    indexer = parseTableIndexer();
+                }
+            }
             else
             {
                 Name propName = parseName("property name");
@@ -916,7 +935,7 @@ AstStat* Parser::parseDeclaration(const Location& start)
         Location classEnd = lexer.current().location;
         nextLexeme(); // skip past `end`
 
-        return allocator.alloc<AstStatDeclareClass>(Location(classStart, classEnd), className.name, superName, copy(props));
+        return allocator.alloc<AstStatDeclareClass>(Location(classStart, classEnd), className.name, superName, copy(props), indexer);
     }
     else if (std::optional<Name> globalName = parseNameOpt("global variable name"))
     {

tests/AstJsonEncoder.test.cpp

@@ -432,11 +432,11 @@ TEST_CASE_FIXTURE(JsonEncoderFixture, "encode_AstStatDeclareClass")
     REQUIRE(2 == root->body.size);
 
     std::string_view expected1 =
-        R"({"type":"AstStatDeclareClass","location":"1,22 - 4,11","name":"Foo","props":[{"name":"prop","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeReference","location":"2,18 - 2,24","name":"number","nameLocation":"2,18 - 2,24","parameters":[]}},{"name":"method","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeFunction","location":"3,21 - 4,11","generics":[],"genericPacks":[],"argTypes":{"type":"AstTypeList","types":[{"type":"AstTypeReference","location":"3,39 - 3,45","name":"number","nameLocation":"3,39 - 3,45","parameters":[]}]},"returnTypes":{"type":"AstTypeList","types":[{"type":"AstTypeReference","location":"3,48 - 3,54","name":"string","nameLocation":"3,48 - 3,54","parameters":[]}]}}}]})";
+        R"({"type":"AstStatDeclareClass","location":"1,22 - 4,11","name":"Foo","props":[{"name":"prop","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeReference","location":"2,18 - 2,24","name":"number","nameLocation":"2,18 - 2,24","parameters":[]}},{"name":"method","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeFunction","location":"3,21 - 4,11","generics":[],"genericPacks":[],"argTypes":{"type":"AstTypeList","types":[{"type":"AstTypeReference","location":"3,39 - 3,45","name":"number","nameLocation":"3,39 - 3,45","parameters":[]}]},"returnTypes":{"type":"AstTypeList","types":[{"type":"AstTypeReference","location":"3,48 - 3,54","name":"string","nameLocation":"3,48 - 3,54","parameters":[]}]}}}],"indexer":null})";
     CHECK(toJson(root->body.data[0]) == expected1);
 
     std::string_view expected2 =
-        R"({"type":"AstStatDeclareClass","location":"6,22 - 8,11","name":"Bar","superName":"Foo","props":[{"name":"prop2","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeReference","location":"7,19 - 7,25","name":"string","nameLocation":"7,19 - 7,25","parameters":[]}}]})";
+        R"({"type":"AstStatDeclareClass","location":"6,22 - 8,11","name":"Bar","superName":"Foo","props":[{"name":"prop2","type":"AstDeclaredClassProp","luauType":{"type":"AstTypeReference","location":"7,19 - 7,25","name":"string","nameLocation":"7,19 - 7,25","parameters":[]}}],"indexer":null})";
     CHECK(toJson(root->body.data[1]) == expected2);
 }
 

tests/Parser.test.cpp

@@ -54,7 +54,8 @@ TEST_SUITE_BEGIN("AllocatorTests");
 TEST_CASE("allocator_can_be_moved")
 {
     Counter* c = nullptr;
-    auto inner = [&]() {
+    auto inner = [&]()
+    {
         Luau::Allocator allocator;
         c = allocator.alloc<Counter>();
         Luau::Allocator moved{std::move(allocator)};
@@ -921,7 +922,8 @@ TEST_CASE_FIXTURE(Fixture, "parse_interpolated_string_double_brace_mid")
 
 TEST_CASE_FIXTURE(Fixture, "parse_interpolated_string_without_end_brace")
 {
-    auto columnOfEndBraceError = [this](const char* code) {
+    auto columnOfEndBraceError = [this](const char* code)
+    {
         try
         {
             parse(code);
@@ -1882,6 +1884,44 @@ TEST_CASE_FIXTURE(Fixture, "class_method_properties")
     CHECK_EQ(2, klass2->props.size);
 }
 
+TEST_CASE_FIXTURE(Fixture, "class_indexer")
+{
+    ScopedFastFlag LuauParseDeclareClassIndexer("LuauParseDeclareClassIndexer", true);
+
+    AstStatBlock* stat = parseEx(R"(
+        declare class Foo
+            prop: boolean
+            [string]: number
+        end
+    )")
+                             .root;
+
+    REQUIRE_EQ(stat->body.size, 1);
+
+    AstStatDeclareClass* declaredClass = stat->body.data[0]->as<AstStatDeclareClass>();
+    REQUIRE(declaredClass);
+    REQUIRE(declaredClass->indexer);
+    REQUIRE(declaredClass->indexer->indexType->is<AstTypeReference>());
+    CHECK(declaredClass->indexer->indexType->as<AstTypeReference>()->name == "string");
+    REQUIRE(declaredClass->indexer->resultType->is<AstTypeReference>());
+    CHECK(declaredClass->indexer->resultType->as<AstTypeReference>()->name == "number");
+
+    const ParseResult p1 = matchParseError(R"(
+        declare class Foo
+            [string]: number
+            -- can only have one indexer
+            [number]: number
+        end
+        )",
+        "Cannot have more than one class indexer");
+
+    REQUIRE_EQ(1, p1.root->body.size);
+
+    AstStatDeclareClass* klass = p1.root->body.data[0]->as<AstStatDeclareClass>();
+    REQUIRE(klass != nullptr);
+    CHECK(klass->indexer);
+}
+
 TEST_CASE_FIXTURE(Fixture, "parse_variadics")
 {
     //clang-format off
@@ -2347,7 +2387,8 @@ public:
 
 TEST_CASE_FIXTURE(Fixture, "recovery_of_parenthesized_expressions")
 {
-    auto checkAstEquivalence = [this](const char* codeWithErrors, const char* code) {
+    auto checkAstEquivalence = [this](const char* codeWithErrors, const char* code)
+    {
         try
         {
             parse(codeWithErrors);
@@ -2367,7 +2408,8 @@ TEST_CASE_FIXTURE(Fixture, "recovery_of_parenthesized_expressions")
         CHECK_EQ(counterWithErrors.count, counter.count);
     };
 
-    auto checkRecovery = [this, checkAstEquivalence](const char* codeWithErrors, const char* code, unsigned expectedErrorCount) {
+    auto checkRecovery = [this, checkAstEquivalence](const char* codeWithErrors, const char* code, unsigned expectedErrorCount)
+    {
         try
         {
             parse(codeWithErrors);

tests/TypeInfer.definitions.test.cpp

@@ -394,6 +394,36 @@ TEST_CASE_FIXTURE(Fixture, "class_definition_string_props")
     CHECK_EQ(toString(requireType("y")), "string");
 }
 
+
+TEST_CASE_FIXTURE(Fixture, "class_definition_indexer")
+{
+    ScopedFastFlag LuauParseDeclareClassIndexer("LuauParseDeclareClassIndexer", true);
+    ScopedFastFlag LuauTypecheckClassTypeIndexers("LuauTypecheckClassTypeIndexers", true);
+
+    loadDefinition(R"(
+        declare class Foo
+            [number]: string
+        end
+    )");
+
+    CheckResult result = check(R"(
+        local x: Foo
+        local y = x[1]
+    )");
+
+    LUAU_REQUIRE_NO_ERRORS(result);
+
+    const ClassType* ctv = get<ClassType>(requireType("x"));
+    REQUIRE(ctv != nullptr);
+
+    REQUIRE(bool(ctv->indexer));
+
+    CHECK_EQ(*ctv->indexer->indexType, *builtinTypes->numberType);
+    CHECK_EQ(*ctv->indexer->indexResultType, *builtinTypes->stringType);
+
+    CHECK_EQ(toString(requireType("y")), "string");
+}
+
 TEST_CASE_FIXTURE(Fixture, "class_definitions_reference_other_classes")
 {
     unfreeze(frontend.globals.globalTypes);