From 97db8166a51a138d942542f81ca5e2cb01d89392 Mon Sep 17 00:00:00 2001
From: Kampfkarren <3190756+Kampfkarren@users.noreply.github.com>
Date: Thu, 28 Nov 2024 22:34:35 -0800
Subject: [PATCH] Fix values preserving nil in iterators
---
Analysis/src/TypeInfer.cpp | 14 +++++++++++++-
tests/TypeInfer.loops.test.cpp | 31 +++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/Analysis/src/TypeInfer.cpp b/Analysis/src/TypeInfer.cpp
index 7ed3290b..b093daba 100644
--- a/Analysis/src/TypeInfer.cpp
+++ b/Analysis/src/TypeInfer.cpp
@@ -34,6 +34,7 @@ LUAU_FASTFLAGVARIABLE(DebugLuauFreezeDuringUnification)
LUAU_FASTFLAG(LuauInstantiateInSubtyping)
LUAU_FASTFLAGVARIABLE(LuauMetatableFollow)
LUAU_FASTFLAGVARIABLE(LuauRequireCyclesDontAlwaysReturnAny)
+LUAU_FASTFLAGVARIABLE(LuauNilInForLoops)
namespace Luau
{
@@ -1285,7 +1286,18 @@ ControlFlow TypeChecker::check(const ScopePtr& scope, const AstStatForIn& forin)
unify(iterTable->indexer->indexType, varTypes[0], scope, forin.location);
if (varTypes.size() > 1)
- unify(iterTable->indexer->indexResultType, varTypes[1], scope, forin.location);
+ {
+ if (FFlag::LuauNilInForLoops)
+ {
+ std::optional<TypeId> withoutNilTy = tryStripUnionFromNil(iterTable->indexer->indexResultType);
+
+ unify(withoutNilTy ? *withoutNilTy : iterTable->indexer->indexResultType, varTypes[1], scope, forin.location);
+ }
+ else
+ {
+ unify(iterTable->indexer->indexResultType, varTypes[1], scope, forin.location);
+ }
+ }
for (size_t i = 2; i < varTypes.size(); ++i)
unify(nilType, varTypes[i], scope, forin.location);
diff --git a/tests/TypeInfer.loops.test.cpp b/tests/TypeInfer.loops.test.cpp
index 41753b66..fa689afe 100644
--- a/tests/TypeInfer.loops.test.cpp
+++ b/tests/TypeInfer.loops.test.cpp
@@ -15,6 +15,7 @@
using namespace Luau;
LUAU_FASTFLAG(LuauSolverV2)
+LUAU_FASTFLAG(LuauNilInForLoops)
TEST_SUITE_BEGIN("TypeInferLoops");
@@ -1255,4 +1256,34 @@ end
)");
}
+TEST_CASE_FIXTURE(Fixture, "nil_in_for_loops")
+{
+ ScopedFastFlag sff = {FFlag::LuauNilInForLoops, true};
+
+ LUAU_REQUIRE_NO_ERRORS(check(R"(
+ --!strict
+ local function f(x: { [string]: string? })
+ for key, value in x do
+ local v: string = value
+ end
+ end
+ )"));
+}
+
+// Custom iterators can return nil, just not without
+TEST_CASE_FIXTURE(BuiltinsFixture, "nil_in_for_loops_iter")
+{
+ LUAU_REQUIRE_NO_ERRORS(check(R"(
+ --!strict
+ type T = typeof(setmetatable({}, {} :: {
+ __iter: (any) -> () -> (boolean, string?)
+ }))
+
+ local function f(x: T)
+ for a: boolean, b: string? in x do
+ end
+ end
+ )"));
+}
+
TEST_SUITE_END();