Relax enforcement on conditional nullability attributes (#46201)

src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs

@@ -502,11 +502,6 @@ void enforceMemberNotNullWhenForPendingReturn(PendingBranch pendingReturn, Bound
                     enforceMemberNotNullWhen(returnStatement.Syntax, sense: true, pendingReturn.StateWhenTrue);
                     enforceMemberNotNullWhen(returnStatement.Syntax, sense: false, pendingReturn.StateWhenFalse);
                 }
-                else
-                {
-                    enforceMemberNotNullWhen(returnStatement.Syntax, sense: true, pendingReturn.State);
-                    enforceMemberNotNullWhen(returnStatement.Syntax, sense: false, pendingReturn.State);
-                }
             }
 
             void enforceMemberNotNullWhen(SyntaxNode syntaxOpt, bool sense, LocalState state)
@@ -605,11 +600,6 @@ void enforceNotNullWhenForPendingReturn(PendingBranch pendingReturn, BoundExpres
                         enforceParameterNotNullWhen(returnStatement.Syntax, parameters, sense: true, stateWhen: pendingReturn.StateWhenTrue);
                         enforceParameterNotNullWhen(returnStatement.Syntax, parameters, sense: false, stateWhen: pendingReturn.StateWhenFalse);
                     }
-                    else
-                    {
-                        enforceParameterNotNullWhen(returnStatement.Syntax, parameters, sense: true, stateWhen: pendingReturn.State);
-                        enforceParameterNotNullWhen(returnStatement.Syntax, parameters, sense: false, stateWhen: pendingReturn.State);
-                    }
                 }
             }
 

src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs

@@ -22385,7 +22385,7 @@ public class C
     bool Init()
     {
         bool b = true;
-        return b; // 2
+        return b;
     }
 }
 ", MemberNotNullWhenAttributeDefinition }, parseOptions: TestOptions.RegularPreview);
@@ -22393,10 +22393,7 @@ bool Init()
             c.VerifyDiagnostics(
                 // (5,19): warning CS8618: Non-nullable field 'field1' is uninitialized. Consider declaring the field as nullable.
                 //     public string field1; // 1
-                Diagnostic(ErrorCode.WRN_UninitializedNonNullableField, "field1").WithArguments("field", "field1").WithLocation(5, 19),
-                // (11,9): warning CS8775: Member 'field1' must have a non-null value when exiting with 'true'.
-                //         return b; // 2
-                Diagnostic(ErrorCode.WRN_MemberNotNullWhen, "return b;").WithArguments("field1", "true").WithLocation(11, 9)
+                Diagnostic(ErrorCode.WRN_UninitializedNonNullableField, "field1").WithArguments("field", "field1").WithLocation(5, 19)
                 );
         }
 
@@ -23798,7 +23795,7 @@ bool Init(bool b)
                 );
         }
 
-        [Fact]
+        [Fact, WorkItem(44080, "https://github.com/dotnet/roslyn/issues/44080")]
         public void MemberNotNullWhenTrue_EnforcedInMethodBody_NonConstantBool()
         {
             var c = CreateNullableCompilation(new[] { @"
@@ -23822,13 +23819,7 @@ bool Init()
             c.VerifyDiagnostics(
                 // (5,19): warning CS8618: Non-nullable field 'field1' is uninitialized. Consider declaring the field as nullable.
                 //     public string field1;
-                Diagnostic(ErrorCode.WRN_UninitializedNonNullableField, "field1").WithArguments("field", "field1").WithLocation(5, 19),
-                // (13,9): warning CS8775: Member 'field1' must have a non-null value when exiting with 'true'.
-                //         return NonConstantBool();
-                Diagnostic(ErrorCode.WRN_MemberNotNullWhen, "return NonConstantBool();").WithArguments("field1", "true").WithLocation(13, 9),
-                // (13,9): warning CS8775: Member 'field3' must have a non-null value when exiting with 'true'.
-                //         return NonConstantBool();
-                Diagnostic(ErrorCode.WRN_MemberNotNullWhen, "return NonConstantBool();").WithArguments("field3", "true").WithLocation(13, 9)
+                Diagnostic(ErrorCode.WRN_UninitializedNonNullableField, "field1").WithArguments("field", "field1").WithLocation(5, 19)
                 );
         }
 
@@ -24613,11 +24604,7 @@ public static bool TryGetValue<T>([MaybeNull] [NotNullWhen(true)] out T t)
 }
 ";
             var comp = CreateNullableCompilation(new[] { source, MaybeNullAttributeDefinition, NotNullWhenAttributeDefinition });
-            comp.VerifyDiagnostics(
-                // (7,9): warning CS8762: Parameter 't' must have a non-null value when exiting with 'true'.
-                //         return TryGetValue2<T>(out t);
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return TryGetValue2<T>(out t);").WithArguments("t", "true").WithLocation(7, 9)
-                );
+            comp.VerifyDiagnostics();
         }
 
         [Fact, WorkItem(39922, "https://github.com/dotnet/roslyn/issues/39922")]
@@ -24826,20 +24813,16 @@ public class C
     public static bool TryGetValue([NotNullWhen(true)] out string? s)
     {
         s = null;
-        return NonConstantBool(); // 1
+        return NonConstantBool();
     }
     static bool NonConstantBool() => throw null!;
 }
 ";
             var comp = CreateNullableCompilation(new[] { source, NotNullWhenAttributeDefinition });
-            comp.VerifyDiagnostics(
-                // (8,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'true'.
-                //         return NonConstantBool(); // 1
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return NonConstantBool();").WithArguments("s", "true").WithLocation(8, 9)
-                );
+            comp.VerifyDiagnostics();
         }
 
-        [Fact, WorkItem(39922, "https://github.com/dotnet/roslyn/issues/39922")]
+        [Fact, WorkItem(39922, "https://github.com/dotnet/roslyn/issues/39922"), WorkItem(44080, "https://github.com/dotnet/roslyn/issues/44080")]
         public void NotNullWhenFalse_EnforceInMethodBody_Warn_NonConstantReturn()
         {
             var source = @"
@@ -24849,17 +24832,13 @@ public class C
     public static bool TryGetValue([NotNullWhen(false)] out string? s)
     {
         s = null;
-        return NonConstantBool(); // 1
+        return NonConstantBool();
     }
     static bool NonConstantBool() => throw null!;
 }
 ";
             var comp = CreateNullableCompilation(new[] { source, NotNullWhenAttributeDefinition });
-            comp.VerifyDiagnostics(
-                // (8,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'false'.
-                //         return NonConstantBool(); // 1
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return NonConstantBool();").WithArguments("s", "false").WithLocation(8, 9)
-                );
+            comp.VerifyDiagnostics();
         }
 
         [Fact, WorkItem(39922, "https://github.com/dotnet/roslyn/issues/39922"), WorkItem(42386, "https://github.com/dotnet/roslyn/issues/42386")]
@@ -25019,7 +24998,7 @@ public static bool TryGetValue(C? c, [NotNullWhen(true)] out string? s)
         return c; // 1
     }
 
-    public static bool TryGetValue2(C c, [NotNullWhen(true)] out string? s)
+    public static bool TryGetValue2(C c, [NotNullWhen(false)] out string? s)
     {
         s = null;
         return c; // 2
@@ -25041,20 +25020,7 @@ static bool TryGetValue4([MaybeNullWhen(false)]out string s)
 }
 ";
             var comp = CreateNullableCompilation(new[] { source, NotNullWhenAttributeDefinition, MaybeNullWhenAttributeDefinition });
-            comp.VerifyDiagnostics(
-                // (8,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'true'.
-                //         return c; // 1
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return c;").WithArguments("s", "true").WithLocation(8, 9),
-                // (14,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'true'.
-                //         return c; // 2
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return c;").WithArguments("s", "true").WithLocation(14, 9),
-                // (22,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'true'.
-                //         return (bool)true; // 3
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return (bool)true;").WithArguments("s", "true").WithLocation(22, 9),
-                // (28,9): warning CS8762: Parameter 's' must have a non-null value when exiting with 'true'.
-                //         return (bool)false; // 4
-                Diagnostic(ErrorCode.WRN_ParameterConditionallyDisallowsNull, "return (bool)false;").WithArguments("s", "true").WithLocation(28, 9)
-                );
+            comp.VerifyDiagnostics();
         }
 
         [Fact]
@@ -133746,6 +133712,42 @@ public new void M1<T>(System.Nullable<T?> x)
                 );
         }
 
+        [Fact, WorkItem(43071, "https://github.com/dotnet/roslyn/issues/43071")]
+        public void LocalFunctionInLambdaWithReturnStatement()
+        {
+            var source = @"
+using System;
+using System.Collections.Generic;
+
+public class C<T>
+{
+    public static C<string> ReproFunction(C<string> collection)
+    {
+        return collection
+            .SelectMany(allStrings =>
+            {
+                return new[] { getSomeString(""custard"") };
+
+                string getSomeString(string substring)
+                {
+                    return substring;
+                }
+        });
+    }
+}
+
+public static class Extension
+{
+    public static C<TResult> SelectMany<TSource, TResult>(this C<TSource> source, Func<TSource, IEnumerable<TResult>> selector)
+    {
+        throw null!;
+    }
+}
+";
+            var comp = CreateNullableCompilation(source);
+            comp.VerifyDiagnostics();
+        }
+
         [Fact]
         [WorkItem(44348, "https://github.com/dotnet/roslyn/issues/44348")]
         public void Constraints()