[beta] [vm, dart2wasm, tfa] Do not infer nullable return type when st…

…atic type is non-nullable

With sound null safety, implicit "return null" at the end of function
should be taken into account only if return type is nullable.

TEST=pkg/vm/testcases/transformations/type_flow/transformer/regress_flutter148617.dart

Issue: flutter/flutter#148617
Change-Id: Iebf68d4b279055fc2f902c36b5fb916bafe7bb8e
Cherry-pick: https://dart-review.googlesource.com/c/sdk/+/367980
Cherry-pick-request: TBA
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/368180
Commit-Queue: Martin Kustermann <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>

pkg/vm/lib/transformations/type_flow/summary_collector.dart

@@ -837,7 +837,8 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
       } else {
         _visitWithoutResult(function.body!);
 
-        if (_currentCondition is! EmptyType) {
+        if (function.returnType.nullability != Nullability.nonNullable &&
+            _currentCondition is! EmptyType) {
           _returnValue!.values.add(_nullType);
         }
       }

pkg/vm/testcases/transformations/ffi/finalizable_sync_star.dart.aot.expect

@@ -46,7 +46,7 @@ static method main() → void {
   final self::MyFinalizable finalizable = new self::MyFinalizable::•();
   {
     synthesized core::Iterator<core::int> :sync-for-iterator = [@vm.direct-call.metadata=dart.async::_SyncStarIterable.iterator] [@vm.inferred-type.metadata=dart.async::_SyncStarIterator] [@vm.inferred-type.metadata=dart.async::_SyncStarIterable] self::useFinalizableSyncStar(finalizable).{core::Iterable::iterator}{core::Iterator<core::int>};
-    for (; [@vm.direct-call.metadata=dart.async::_SyncStarIterator.moveNext] [@vm.inferred-type.metadata=dart.core::bool? (skip check)] :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
+    for (; [@vm.direct-call.metadata=dart.async::_SyncStarIterator.moveNext] [@vm.inferred-type.metadata=dart.core::bool (skip check)] :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
       final core::int element = [@vm.direct-call.metadata=dart.async::_SyncStarIterator.current] [@vm.inferred-type.metadata=int] :sync-for-iterator.{core::Iterator::current}{core::int};
       {
         core::print(element);

pkg/vm/testcases/transformations/type_flow/summary_collector/calls.dart.expect

@@ -1,15 +1,15 @@
 ------------ A. ------------
 %this = _Parameter #0 [_T (#lib::A)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ A.foo1 ------------
 %this = _Parameter #0 [_T (#lib::A)+]
 %x = _Parameter #1 [_T (dart.core::Object)+]
 RESULT: _T {}?
 ------------ B. ------------
 %this = _Parameter #0 [_T (#lib::B)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ B.bar1 ------------
 %this = _Parameter #0 [_T (#lib::B)+]
 %arg = _Parameter #1 [_T (dart.core::Object)+]
@@ -27,7 +27,7 @@ RESULT: _T {}?
 ------------ C. ------------
 %this = _Parameter #0 [_T (#lib::C)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C.interfaceCalls ------------
 %this = _Parameter #0 [_T (#lib::C)+]
 %aa = _Parameter #1 [_T (#lib::A)+]
@@ -61,7 +61,7 @@ RESULT: t11
 ------------ D. ------------
 %this = _Parameter #0 [_T (#lib::D)+]
 t1 = _Call direct [#lib::B.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ D.superCalls ------------
 %this = _Parameter #0 [_T (#lib::D)+]
 %a1 = _Parameter #1 [_T (dart.core::Object)+]

pkg/vm/testcases/transformations/type_flow/summary_collector/class_generics_basic.dart.expect

@@ -1,7 +1,7 @@
 ------------ C. ------------
 %this = _Parameter #0 [_T (#lib::C)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C.foo ------------
 %this = _Parameter #0 [_T (#lib::C)+]
 t1 = _Extract (%this[#lib::C/0])
@@ -23,11 +23,11 @@ RESULT: t3
 ------------ D. ------------
 %this = _Parameter #0 [_T (#lib::D)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ E. ------------
 %this = _Parameter #0 [_T (#lib::E)+]
 t1 = _Call direct [#lib::C.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ E.foo ------------
 %this = _Parameter #0 [_T (#lib::E)+]
 t1* = _Call direct [#lib::C.foo] (%this)
@@ -47,31 +47,31 @@ RESULT: t3
 ------------ X. ------------
 %this = _Parameter #0 [_T (#lib::X)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ Y. ------------
 %this = _Parameter #0 [_T (#lib::Y)+]
 t1 = _Call direct [#lib::X.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ Z. ------------
 %this = _Parameter #0 [_T (#lib::Z)+]
 t1 = _Call direct [#lib::X.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ I. ------------
 %this = _Parameter #0 [_T (#lib::I)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ J. ------------
 %this = _Parameter #0 [_T (#lib::J)+]
 t1 = _Call direct [#lib::I.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ K. ------------
 %this = _Parameter #0 [_T (#lib::K)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C2. ------------
 %this = _Parameter #0 [_T (#lib::C2)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C2.id3 ------------
 %this = _Parameter #0 [_T (#lib::C2)+]
 %x = _Parameter #1

pkg/vm/testcases/transformations/type_flow/summary_collector/class_generics_case1.dart.expect

@@ -1,7 +1,7 @@
 ------------ Element. ------------
 %this = _Parameter #0 [_T (#lib::Element)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ MockHashMap. ------------
 %K = _Parameter #0
 %V = _Parameter #1
@@ -11,7 +11,7 @@ RESULT: t3
 ------------ _NotRealHashMap. ------------
 %this = _Parameter #0 [_T (#lib::_NotRealHashMap)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ _NotRealHashMap.setEntry ------------
 %this = _Parameter #0 [_T (#lib::_NotRealHashMap)+]
 %key = _Parameter #1
@@ -24,7 +24,7 @@ RESULT: _T {}?
 ------------ InheritedElement. ------------
 %this = _Parameter #0 [_T (#lib::InheritedElement)+]
 t1 = _Call direct [#lib::Element.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ InheritedElement.setDependencies ------------
 %this = _Parameter #0 [_T (#lib::InheritedElement)+]
 %dependent = _Parameter #1 [_T (#lib::Element)+]

pkg/vm/testcases/transformations/type_flow/summary_collector/control_flow.dart.expect

@@ -1,29 +1,29 @@
 ------------ C1. ------------
 %this = _Parameter #0 [_T (#lib::C1)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C2. ------------
 %this = _Parameter #0 [_T (#lib::C2)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C3. ------------
 %this = _Parameter #0 [_T (#lib::C3)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C4. ------------
 %this = _Parameter #0 [_T (#lib::C4)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ C5. ------------
 %this = _Parameter #0 [_T (#lib::C5)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ TestEnum. ------------
 %this = _Parameter #0 [_T (#lib::TestEnum)+]
 %#index = _Parameter #1 [_T (dart.core::int)+]
 %#name = _Parameter #2 [_T (dart.core::String)+]
 t3 = _Call direct [dart.core::_Enum.] (%this, %#index, %#name)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ TestEnum._enumToString ------------
 %this = _Parameter #0 [_T (#lib::TestEnum)+]
 t1 = _Call virtual get [dart.core::_Enum._name] (%this)

pkg/vm/testcases/transformations/type_flow/summary_collector/implicit_return_null.dart.expect

@@ -1,7 +1,7 @@
 ------------ T. ------------
 %this = _Parameter #0 [_T (#lib::T)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ empty1 ------------
 
 RESULT: _T {}?

pkg/vm/testcases/transformations/type_flow/summary_collector/setter_result.dart.expect

@@ -1,18 +1,18 @@
 ------------ T. ------------
 %this = _Parameter #0 [_T (#lib::T)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ A. ------------
 %this = _Parameter #0 [_T (#lib::A)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ A.foo ------------
 %this = _Parameter #0 [_T (#lib::A)+]
 RESULT: _T {}?
 ------------ B. ------------
 %this = _Parameter #0 [_T (#lib::B)+]
 t1 = _Call direct [#lib::A.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ B.foo ------------
 %this = _Parameter #0 [_T (#lib::B)+]
 %x = _Parameter #1 [_T ANY?]

pkg/vm/testcases/transformations/type_flow/summary_collector/vars.dart.expect

@@ -1,11 +1,11 @@
 ------------ A. ------------
 %this = _Parameter #0 [_T (#lib::A)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ B. ------------
 %this = _Parameter #0 [_T (#lib::B)+]
 t1 = _Call direct [dart.core::Object.] (%this)
-RESULT: _T {}?
+RESULT: _T {}
 ------------ foo ------------
 %a1 = _Parameter #0 [_T (dart.core::Object)+]
 %a2 = _Parameter #1 [_T (dart.core::Object)+?]

pkg/vm/testcases/transformations/type_flow/transformer/bench_is_prime.dart.expect

@@ -16,7 +16,8 @@ static method isPrime([@vm.inferred-arg-type.metadata=int] dynamic n) → core::
   return true;
 }
 
-[@vm.inferred-return-type.metadata=int?]
+[@vm.inferred-return-type.metadata=int]
+[@vm.unboxing-info.metadata=()->i]
 static method nThPrimeNumber() → core::int {
   core::int counter = 0;
   for (core::int i = 1; ; i = [@vm.direct-call.metadata=dart.core::_IntegerImplementation.+] [@vm.inferred-type.metadata=int (skip check)] i.{core::num::+}(1){(core::num) → core::int}) {
@@ -31,7 +32,7 @@ static method nThPrimeNumber() → core::int {
 [@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
 static method run() → void {
   core::int e = 611953;
-  core::int p = [@vm.inferred-type.metadata=int?] self::nThPrimeNumber();
+  core::int p = [@vm.inferred-type.metadata=int] self::nThPrimeNumber();
   if(!([@vm.direct-call.metadata=dart.core::_IntegerImplementation.==] [@vm.inferred-type.metadata=dart.core::bool (skip check)] p =={core::num::==}{(core::Object) → core::bool} e)) {
     throw core::Exception::•("Unexpected result: ${p} != ${e}");
   }

pkg/vm/testcases/transformations/type_flow/transformer/regress_flutter148617.dart

@@ -0,0 +1,21 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Regression test for https://github.com/flutter/flutter/issues/148617.
+// Verifies that TFA should not infer nullable return type if
+// static return type is non-nullable.
+
+int foo() => int.parse('1');
+
+int bar() {
+  try {
+    return foo();
+  } catch (e, st) {
+    Error.throwWithStackTrace(e, st);
+  }
+}
+
+main() {
+  print(bar());
+}

pkg/vm/testcases/transformations/type_flow/transformer/regress_flutter148617.dart.expect

@@ -0,0 +1,25 @@
+library #lib;
+import self as self;
+import "dart:core" as core;
+
+
+[@vm.inferred-return-type.metadata=int]
+[@vm.unboxing-info.metadata=()->i]
+static method foo() → core::int
+  return [@vm.inferred-type.metadata=int] core::int::parse("1");
+
+[@vm.inferred-return-type.metadata=int]
+[@vm.unboxing-info.metadata=()->i]
+static method bar() → core::int {
+  try {
+    return [@vm.inferred-type.metadata=int] self::foo();
+  }
+  on core::Object catch(final core::Object e, final core::StackTrace st) {
+    core::Error::throwWithStackTrace(e, st);
+  }
+}
+
+[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
+static method main() → dynamic {
+  core::print([@vm.inferred-type.metadata=int] self::bar());
+}