Require partial method signatures to match (#47576)

* Require partial method signatures to match

* Revert changes

* Fix tests

* Fix tests

* Avoid duplicate errors for tuples

* Fix tests

* Update numbering

* Add distinct error for nullability mismatch

* PR feedback

* Another test

* Fix test

* Add warning wave warning

* Update comments

* Remove stale comments

* PR feedback

* Fix test

* PR feedback

* Update comments in CopyTypeCustomModifiers()

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -6305,6 +6305,12 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_PartialMethodRefReturnDifference" xml:space="preserve">
     <value>Partial method declarations must have matching ref return values.</value>
   </data>
+  <data name="WRN_PartialMethodTypeDifference" xml:space="preserve">
+    <value>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</value>
+  </data>
+  <data name="WRN_PartialMethodTypeDifference_Title" xml:space="preserve">
+    <value>Partial method declarations have differences in parameter or return types.</value>
+  </data>
   <data name="IDS_TopLevelStatements" xml:space="preserve">
     <value>top-level statements</value>
   </data>

src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

@@ -1834,6 +1834,7 @@ internal enum ErrorCode
         ERR_StaticAnonymousFunctionCannotCaptureThis = 8821,
         ERR_OverrideDefaultConstraintNotSatisfied = 8822,
         ERR_DefaultConstraintOverrideOnly = 8823,
+        WRN_PartialMethodTypeDifference = 8824,
 
         ERR_RuntimeDoesNotSupportCovariantReturnsOfClasses = 8830,
         ERR_RuntimeDoesNotSupportCovariantPropertiesOfClasses = 8831,

src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs

@@ -231,6 +231,7 @@ internal static int GetWarningLevel(ErrorCode code)
                 case ErrorCode.WRN_SyncAndAsyncEntryPoints:
                 case ErrorCode.WRN_ParameterIsStaticClass:
                 case ErrorCode.WRN_ReturnTypeIsStaticClass:
+                case ErrorCode.WRN_PartialMethodTypeDifference:
                     // Warning level 5 is exclusively for warnings introduced in the compiler
                     // shipped with dotnet 5 (C# 9) and that can be reported for pre-existing code.
                     return 5;

src/Compilers/CSharp/Portable/Generated/ErrorFacts.Generated.cs

@@ -247,6 +247,7 @@ public static bool IsWarning(ErrorCode code)
                 case ErrorCode.WRN_GivenExpressionAlwaysMatchesPattern:
                 case ErrorCode.WRN_IsPatternAlways:
                 case ErrorCode.WRN_NullabilityMismatchInReturnTypeOnPartial:
+                case ErrorCode.WRN_PartialMethodTypeDifference:
                 case ErrorCode.WRN_SwitchExpressionNotExhaustiveWithWhen:
                 case ErrorCode.WRN_SwitchExpressionNotExhaustiveForNullWithWhen:
                 case ErrorCode.WRN_PrecedenceInversion:

src/Compilers/CSharp/Portable/Symbols/MemberSignatureComparer.cs

@@ -6,7 +6,6 @@
 using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Linq;
-using Microsoft.CodeAnalysis.PooledObjects;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.Symbols
@@ -127,6 +126,19 @@ internal class MemberSignatureComparer : IEqualityComparer<Symbol>
             considerRefKindDifferences: true,
             typeComparison: TypeCompareKind.AllIgnoreOptions);
 
+        /// <summary>
+        /// This instance is used to determine if a partial method implementation matches the definition,
+        /// including differences ignored by the runtime.
+        /// </summary>
+        public static readonly MemberSignatureComparer PartialMethodsStrictComparer = new MemberSignatureComparer(
+            considerName: true,
+            considerExplicitlyImplementedInterfaces: true,
+            considerReturnType: true,
+            considerTypeConstraints: false,
+            considerCallingConvention: false,
+            considerRefKindDifferences: true,
+            typeComparison: TypeCompareKind.ObliviousNullableModifierMatchesAny);
+
         /// <summary>
         /// This instance is used to check whether one member overrides another, according to the C# definition.
         /// </summary>

src/Compilers/CSharp/Portable/Symbols/Source/CustomModifierUtils.cs

@@ -60,7 +60,8 @@ internal static class CustomModifierUtils
         }
 
         /// <param name="sourceType">Type that already has custom modifiers.</param>
-        /// <param name="destinationType">Same as <paramref name="sourceType"/>, but without custom modifiers.  May differ in object/dynamic.</param>
+        /// <param name="destinationType">Same as <paramref name="sourceType"/>, but without custom modifiers.
+        /// May differ in object/dynamic, tuple element names, or other differences ignored by the runtime.</param>
         /// <param name="containingAssembly">The assembly containing the signature referring to the destination type.</param>
         /// <returns><paramref name="destinationType"/> with custom modifiers copied from <paramref name="sourceType"/>.</returns>
         internal static TypeSymbol CopyTypeCustomModifiers(TypeSymbol sourceType, TypeSymbol destinationType, AssemblySymbol containingAssembly)
@@ -69,10 +70,9 @@ internal static TypeSymbol CopyTypeCustomModifiers(TypeSymbol sourceType, TypeSy
 
             const RefKind refKind = RefKind.None;
 
-            // NOTE: overrides can differ by object/dynamic.  If they do, we'll need to tweak newType before
-            // we can use it in place of this.Type.  We do so by computing the dynamic transform flags that
-            // code gen uses and then passing them to the dynamic type decoder that metadata reading uses.
-            // NOTE: ref is irrelevant here since we are just encoding/decoding the type out of the signature context
+            // NOTE: overrides can differ by object/dynamic, tuple element names, etc.
+            // If they do, we'll need to tweak destinationType before we can use it in place of sourceType.
+            // NOTE: refKind is irrelevant here since we are just encoding/decoding the type.
             ImmutableArray<bool> flags = CSharpCompilation.DynamicTransformsEncoder.EncodeWithoutCustomModifierFlags(destinationType, refKind);
             TypeSymbol resultType = DynamicTypeDecoder.TransformTypeWithoutCustomModifierFlags(sourceType, containingAssembly, refKind, flags);
 

src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs

@@ -2653,10 +2653,6 @@ internal Binder GetBinder(CSharpSyntaxNode syntaxNode)
                     {
                         diagnostics.Add(ErrorCode.ERR_PartialMethodMustHaveLatent, method.Locations[0], method);
                     }
-                    else if (!(method.OtherPartOfPartial is null) && MemberSignatureComparer.ConsideringTupleNamesCreatesDifference(method, method.OtherPartOfPartial))
-                    {
-                        diagnostics.Add(ErrorCode.ERR_PartialMethodInconsistentTupleNames, method.Locations[0], method, method.OtherPartOfPartial);
-                    }
                     else if (method is { IsPartialDefinition: true, OtherPartOfPartial: null, HasExplicitAccessModifier: true })
                     {
                         diagnostics.Add(ErrorCode.ERR_PartialMethodWithAccessibilityModsMustHaveImplementation, method.Locations[0], method);

src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol_ImplementationChecks.cs

@@ -1174,7 +1174,7 @@ private bool IsValidOverrideReturnType(Symbol overridingSymbol, TypeWithAnnotati
                 location,
                 new FormattedSymbol(overridingParameter, SymbolDisplayFormat.ShortFormat));
 
-        internal static void CheckValidNullableMethodOverride<TArg>(
+        internal static bool CheckValidNullableMethodOverride<TArg>(
             CSharpCompilation compilation,
             MethodSymbol baseMethod,
             MethodSymbol overrideMethod,
@@ -1186,13 +1186,16 @@ private bool IsValidOverrideReturnType(Symbol overridingSymbol, TypeWithAnnotati
         {
             if (!PerformValidNullableOverrideCheck(compilation, baseMethod, overrideMethod))
             {
-                return;
+                return false;
             }
 
+            bool hasErrors = false;
+
             if ((baseMethod.FlowAnalysisAnnotations & FlowAnalysisAnnotations.DoesNotReturn) == FlowAnalysisAnnotations.DoesNotReturn &&
                 (overrideMethod.FlowAnalysisAnnotations & FlowAnalysisAnnotations.DoesNotReturn) != FlowAnalysisAnnotations.DoesNotReturn)
             {
                 diagnostics.Add(ErrorCode.WRN_DoesNotReturnMismatch, overrideMethod.Locations[0], new FormattedSymbol(overrideMethod, SymbolDisplayFormat.MinimallyQualifiedFormat));
+                hasErrors = true;
             }
 
             var conversions = compilation.Conversions.WithNullability(true);
@@ -1211,7 +1214,7 @@ private bool IsValidOverrideReturnType(Symbol overridingSymbol, TypeWithAnnotati
                         baseMethod.ReturnTypeWithAnnotations.Type))
                 {
                     reportMismatchInReturnType(diagnostics, baseMethod, overrideMethod, false, extraArgument);
-                    return;
+                    return true;
                 }
 
                 // check top-level nullability including flow analysis annotations
@@ -1223,42 +1226,44 @@ private bool IsValidOverrideReturnType(Symbol overridingSymbol, TypeWithAnnotati
                         overrideMethod.ReturnTypeFlowAnalysisAnnotations))
                 {
                     reportMismatchInReturnType(diagnostics, baseMethod, overrideMethod, true, extraArgument);
-                    return;
+                    return true;
                 }
             }
 
-            if (reportMismatchInParameterType == null)
-            {
-                return;
-            }
-
-            for (int i = 0; i < baseParameters.Length; i++)
+            if (reportMismatchInParameterType != null)
             {
-                var baseParameter = baseParameters[i];
-                var baseParameterType = baseParameter.TypeWithAnnotations;
-                var overrideParameter = overrideParameters[i + overrideParameterOffset];
-                var overrideParameterType = getNotNullIfNotNullOutputType(overrideParameter.TypeWithAnnotations, overrideParameter.NotNullIfParameterNotNull);
-                // check nested nullability
-                if (!isValidNullableConversion(
-                        conversions,
-                        overrideParameter.RefKind,
-                        baseParameterType.Type,
-                        overrideParameterType.Type))
-                {
-                    reportMismatchInParameterType(diagnostics, baseMethod, overrideMethod, overrideParameter, false, extraArgument);
-                }
-                // check top-level nullability including flow analysis annotations
-                else if (!NullableWalker.AreParameterAnnotationsCompatible(
-                        overrideParameter.RefKind,
-                        baseParameterType,
-                        baseParameter.FlowAnalysisAnnotations,
-                        overrideParameterType,
-                        overrideParameter.FlowAnalysisAnnotations))
+                for (int i = 0; i < baseParameters.Length; i++)
                 {
-                    reportMismatchInParameterType(diagnostics, baseMethod, overrideMethod, overrideParameter, true, extraArgument);
+                    var baseParameter = baseParameters[i];
+                    var baseParameterType = baseParameter.TypeWithAnnotations;
+                    var overrideParameter = overrideParameters[i + overrideParameterOffset];
+                    var overrideParameterType = getNotNullIfNotNullOutputType(overrideParameter.TypeWithAnnotations, overrideParameter.NotNullIfParameterNotNull);
+                    // check nested nullability
+                    if (!isValidNullableConversion(
+                            conversions,
+                            overrideParameter.RefKind,
+                            baseParameterType.Type,
+                            overrideParameterType.Type))
+                    {
+                        reportMismatchInParameterType(diagnostics, baseMethod, overrideMethod, overrideParameter, false, extraArgument);
+                        hasErrors = true;
+                    }
+                    // check top-level nullability including flow analysis annotations
+                    else if (!NullableWalker.AreParameterAnnotationsCompatible(
+                            overrideParameter.RefKind,
+                            baseParameterType,
+                            baseParameter.FlowAnalysisAnnotations,
+                            overrideParameterType,
+                            overrideParameter.FlowAnalysisAnnotations))
+                    {
+                        reportMismatchInParameterType(diagnostics, baseMethod, overrideMethod, overrideParameter, true, extraArgument);
+                        hasErrors = true;
+                    }
                 }
             }
 
+            return hasErrors;
+
             TypeWithAnnotations getNotNullIfNotNullOutputType(TypeWithAnnotations outputType, ImmutableHashSet<string> notNullIfParameterNotNull)
             {
                 if (!notNullIfParameterNotNull.IsEmpty)

src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

@@ -602,13 +602,16 @@ private static void PartialMethodChecks(SourceOrdinaryMethodSymbol definition, S
             Debug.Assert(!ReferenceEquals(definition, implementation));
 
             MethodSymbol constructedDefinition = definition.ConstructIfGeneric(implementation.TypeArgumentsWithAnnotations);
-            bool returnTypesEqual = constructedDefinition.ReturnTypeWithAnnotations.Equals(implementation.ReturnTypeWithAnnotations, TypeCompareKind.AllIgnoreOptions);
-            if (!returnTypesEqual
-                && !SourceMemberContainerTypeSymbol.IsOrContainsErrorType(implementation.ReturnType)
-                && !SourceMemberContainerTypeSymbol.IsOrContainsErrorType(definition.ReturnType))
+            bool hasTypeDifferences = !constructedDefinition.ReturnTypeWithAnnotations.Equals(implementation.ReturnTypeWithAnnotations, TypeCompareKind.AllIgnoreOptions);
+            if (hasTypeDifferences)
             {
                 diagnostics.Add(ErrorCode.ERR_PartialMethodReturnTypeDifference, implementation.Locations[0]);
             }
+            else if (MemberSignatureComparer.ConsideringTupleNamesCreatesDifference(definition, implementation))
+            {
+                hasTypeDifferences = true;
+                diagnostics.Add(ErrorCode.ERR_PartialMethodInconsistentTupleNames, implementation.Locations[0], definition, implementation);
+            }
 
             if (definition.RefKind != implementation.RefKind)
             {
@@ -656,24 +659,32 @@ private static void PartialMethodChecks(SourceOrdinaryMethodSymbol definition, S
 
             PartialMethodConstraintsChecks(definition, implementation, diagnostics);
 
-            SourceMemberContainerTypeSymbol.CheckValidNullableMethodOverride(
+            if (SourceMemberContainerTypeSymbol.CheckValidNullableMethodOverride(
                 implementation.DeclaringCompilation,
                 constructedDefinition,
                 implementation,
                 diagnostics,
-                (diagnostics, implementedMethod, implementingMethod, topLevel, returnTypesEqual) =>
+                static (diagnostics, implementedMethod, implementingMethod, topLevel, arg) =>
                 {
-                    if (returnTypesEqual)
-                    {
-                        // report only if this is an unsafe *nullability* difference
-                        diagnostics.Add(ErrorCode.WRN_NullabilityMismatchInReturnTypeOnPartial, implementingMethod.Locations[0]);
-                    }
+                    // report only if this is an unsafe *nullability* difference
+                    diagnostics.Add(ErrorCode.WRN_NullabilityMismatchInReturnTypeOnPartial, implementingMethod.Locations[0]);
                 },
-                (diagnostics, implementedMethod, implementingMethod, implementingParameter, blameAttributes, arg) =>
+                static (diagnostics, implementedMethod, implementingMethod, implementingParameter, blameAttributes, arg) =>
                 {
                     diagnostics.Add(ErrorCode.WRN_NullabilityMismatchInParameterTypeOnPartial, implementingMethod.Locations[0], new FormattedSymbol(implementingParameter, SymbolDisplayFormat.ShortFormat));
                 },
-                extraArgument: returnTypesEqual);
+                extraArgument: (object)null))
+            {
+                hasTypeDifferences = true;
+            }
+
+            if (!hasTypeDifferences &&
+                !MemberSignatureComparer.PartialMethodsStrictComparer.Equals(definition, implementation))
+            {
+                diagnostics.Add(ErrorCode.WRN_PartialMethodTypeDifference, implementation.Locations[0],
+                    new FormattedSymbol(definition, SymbolDisplayFormat.MinimallyQualifiedFormat),
+                    new FormattedSymbol(implementation, SymbolDisplayFormat.MinimallyQualifiedFormat));
+            }
         }
 
         private static void PartialMethodConstraintsChecks(SourceOrdinaryMethodSymbol definition, SourceOrdinaryMethodSymbol implementation, DiagnosticBag diagnostics)

src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Typ odkazu s možnou hodnotou null ve vráceném typu neodpovídá přepsanému členu.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Typ odkazu s možnou hodnotou null v typu neodpovídá implementovanému členu {0}.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Die NULL-Zulässigkeit von Verweistypen im Rückgabetyp entspricht nicht dem außer Kraft gesetzten Member.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Die NULL-Zulässigkeit von Verweistypen im Typ entspricht nicht dem implementierten Member "{0}".</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">La nulabilidad de los tipos de referencia en el tipo de valor devuelto no coincide con el miembro reemplazado</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">La nulabilidad de los tipos de referencia del tipo no coincide con el miembro implementado "{0}".</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">La nullabilité des types référence dans le type de retour ne correspond pas au membre substitué.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">La nullabilité des types référence dans le type ne correspond pas au membre implémenté '{0}'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Il supporto dei valori Null dei tipi riferimento nel tipo restituito non corrisponde al membro di cui è stato eseguito l'override.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Il supporto dei valori Null dei tipi riferimento nel tipo non corrisponde al membro implementato '{0}'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">戻り値の型における参照型の Null 許容性が、オーバーライドされるメンバーと一致しません。</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">型における参照型の Null 許容性が、実装されるメンバー '{0}' と一致しません。</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">반환 형식에 있는 참조 형식 Null 허용 여부가 재정의된 멤버와 일치하지 않습니다.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">형식에 있는 참조 형식 Null 허용 여부가 구현된 멤버 '{0}'과(와) 일치하지 않습니다.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Obsługa wartości null dla typów referencyjnych w typie zwracanym jest niezgodna z przesłoniętą składową.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Obsługa wartości null dla typów referencyjnych w typie jest niezgodna z implementowaną składową „{0}”.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2452,16 +2472,6 @@
         <target state="translated">A anulabilidade de tipos de referência em tipo de retorno não corresponde ao membro substituído.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">A anulabilidade de tipos de referência em tipo não corresponde ao membro implementado '{0}'.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Допустимость значения NULL для ссылочных типов в возвращаемом типе не совпадает с переопределенным членом.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Допустимость значения NULL для ссылочных типов в типе не совпадает с реализованным членом "{0}".</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">Dönüş türündeki başvuru türlerinin boş değer atanabilirliği, geçersiz kılınan üye ile eşleşmiyor.</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">Türdeki başvuru türlerinin boş değer atanabilirliği, uygulanan '{0}' üyesi ile eşleşmiyor.</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">返回类型中引用类型的为 Null 性与重写成员不匹配。</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">类型中引用类型的为 Null 性与实现的成员“{0}”不匹配。</target>

src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf

@@ -912,6 +912,26 @@
         <target state="new">discards</target>
         <note />
       </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
+        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
+        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference">
+        <source>Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations '{0}' and '{1}' have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="WRN_PartialMethodTypeDifference_Title">
+        <source>Partial method declarations have differences in parameter or return types.</source>
+        <target state="new">Partial method declarations have differences in parameter or return types.</target>
+        <note />
+      </trans-unit>
       <trans-unit id="WRN_RecordNamedDisallowed">
         <source>Types and aliases should not be named 'record'.</source>
         <target state="new">Types and aliases should not be named 'record'.</target>
@@ -2454,16 +2474,6 @@
         <target state="translated">傳回型別中參考型別的可 Null 性與覆寫的成員不符合。</target>
         <note />
       </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="WRN_NullabilityMismatchInReturnTypeOnPartial_Title">
-        <source>Nullability of reference types in return type doesn't match partial method declaration.</source>
-        <target state="new">Nullability of reference types in return type doesn't match partial method declaration.</target>
-        <note />
-      </trans-unit>
       <trans-unit id="WRN_NullabilityMismatchInTypeOnExplicitImplementation">
         <source>Nullability of reference types in type doesn't match implemented member '{0}'.</source>
         <target state="translated">型別中參考型別的可 Null 性與實作的成員 '{0}' 不符合。</target>

src/Compilers/CSharp/Test/Emit/Attributes/AttributeTests_NativeInteger.cs

@@ -1249,6 +1249,7 @@ static void Main()
         }
 
         [Fact]
+        [WorkItem(45519, "https://github.com/dotnet/roslyn/issues/45519")]
         public void EmitAttribute_PartialMethods()
         {
             var source =
@@ -1260,13 +1261,21 @@ public void EmitAttribute_PartialMethods()
     static partial void F2(nuint x);
 }";
             var comp = CreateCompilation(source, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All), parseOptions: TestOptions.Regular9);
-            // Ideally should not emit any attributes. Compare with dynamic/object.
             var expected =
 @"Program
     void F2(System.UIntPtr x)
         [NativeInteger] System.UIntPtr x
 ";
             AssertNativeIntegerAttributes(comp, expected);
+
+            comp = CreateCompilation(source, options: TestOptions.ReleaseDllWithWarningLevel5, parseOptions: TestOptions.Regular9);
+            comp.VerifyEmitDiagnostics(
+                // (4,25): warning CS8824: Partial method declarations 'void Program.F2(nuint x)' and 'void Program.F2(UIntPtr x)' have differences in parameter or return types.
+                //     static partial void F2(System.UIntPtr x) { }
+                Diagnostic(ErrorCode.WRN_PartialMethodTypeDifference, "F2").WithArguments("void Program.F2(nuint x)", "void Program.F2(UIntPtr x)").WithLocation(4, 25),
+                // (5,25): warning CS8824: Partial method declarations 'void Program.F1(IntPtr x)' and 'void Program.F1(nint x)' have differences in parameter or return types.
+                //     static partial void F1(nint x) { }
+                Diagnostic(ErrorCode.WRN_PartialMethodTypeDifference, "F1").WithArguments("void Program.F1(IntPtr x)", "void Program.F1(nint x)").WithLocation(5, 25));
         }
 
         // Shouldn't depend on [NullablePublicOnly].

src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs

@@ -20509,12 +20509,12 @@ public partial class C
 ";
             var comp = CreateCompilation(source);
             comp.VerifyDiagnostics(
-                // (4,18): error CS8142: Both partial method declarations, 'C.M1((int a, int b))' and 'C.M1((int notA, int notB))', must use the same tuple element names.
-                //     partial void M1((int a, int b) x);
-                Diagnostic(ErrorCode.ERR_PartialMethodInconsistentTupleNames, "M1").WithArguments("C.M1((int a, int b))", "C.M1((int notA, int notB))").WithLocation(4, 18),
-                // (5,18): error CS8142: Both partial method declarations, 'C.M2((int a, int b))' and 'C.M2((int, int))', must use the same tuple element names.
-                //     partial void M2((int a, int b) x);
-                Diagnostic(ErrorCode.ERR_PartialMethodInconsistentTupleNames, "M2").WithArguments("C.M2((int a, int b))", "C.M2((int, int))").WithLocation(5, 18)
+                // (10,18): error CS8142: Both partial method declarations, 'C.M1((int a, int b))' and 'C.M1((int notA, int notB))', must use the same tuple element names.
+                //     partial void M1((int notA, int notB) y) { }
+                Diagnostic(ErrorCode.ERR_PartialMethodInconsistentTupleNames, "M1").WithArguments("C.M1((int a, int b))", "C.M1((int notA, int notB))").WithLocation(10, 18),
+                // (11,18): error CS8142: Both partial method declarations, 'C.M2((int a, int b))' and 'C.M2((int, int))', must use the same tuple element names.
+                //     partial void M2((int, int) y) { }
+                Diagnostic(ErrorCode.ERR_PartialMethodInconsistentTupleNames, "M2").WithArguments("C.M2((int a, int b))", "C.M2((int, int))").WithLocation(11, 18)
                 );
         }
 

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

@@ -3304,6 +3304,7 @@ class C2 : IA, IB
         }
 
         [Fact]
+        [WorkItem(45519, "https://github.com/dotnet/roslyn/issues/45519")]
         public void Partial_01()
         {
             var source =
@@ -3316,6 +3317,15 @@ public void Partial_01()
 }";
             var comp = CreateCompilation(source, parseOptions: TestOptions.Regular9);
             comp.VerifyDiagnostics();
+
+            comp = CreateCompilation(source, options: TestOptions.ReleaseDllWithWarningLevel5, parseOptions: TestOptions.Regular9);
+            comp.VerifyDiagnostics(
+                // (4,25): warning CS8824: Partial method declarations 'void Program.F2(nuint x)' and 'void Program.F2(UIntPtr x)' have differences in parameter or return types.
+                //     static partial void F2(System.UIntPtr x) { }
+                Diagnostic(ErrorCode.WRN_PartialMethodTypeDifference, "F2").WithArguments("void Program.F2(nuint x)", "void Program.F2(UIntPtr x)").WithLocation(4, 25),
+                // (5,25): warning CS8824: Partial method declarations 'void Program.F1(IntPtr x)' and 'void Program.F1(nint x)' have differences in parameter or return types.
+                //     static partial void F1(nint x) { }
+                Diagnostic(ErrorCode.WRN_PartialMethodTypeDifference, "F1").WithArguments("void Program.F1(IntPtr x)", "void Program.F1(nint x)").WithLocation(5, 25));
         }
 
         [Fact]

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

@@ -17694,7 +17694,6 @@ partial class C1
     { }
 }";
             var compilation = CreateCompilation(new[] { source }, options: WithNonNullTypesTrue());
-            // https://github.com/dotnet/roslyn/issues/30145: What nullability is getting emitted?
             compilation.VerifyDiagnostics(
                  // (16,18): warning CS8611: Nullability of reference types in type of parameter 'y' doesn't match partial method declaration.
                  //     partial void M1<T>(T? x, T[]? y, System.Action<T?> z, System.Action<T?[]?>?[]? u) where T : class
@@ -17705,7 +17704,6 @@ partial class C1
                 );
 
             var c1 = compilation.GetTypeByMetadataName("C1");
-
             var m1 = c1.GetMember<MethodSymbol>("M1");
             var m1Impl = m1.PartialImplementationPart;
             var m1Def = m1.ConstructIfGeneric(m1Impl.TypeParameters.SelectAsArray(t => TypeWithAnnotations.Create(t)));
@@ -17718,6 +17716,11 @@ partial class C1
 
             Assert.True(m1Impl.Parameters[3].TypeWithAnnotations.Equals(m1Def.Parameters[3].TypeWithAnnotations,
                 TypeCompareKind.AllIgnoreOptions & ~TypeCompareKind.AllNullableIgnoreOptions));
+
+            compilation = CreateCompilation("", references: new[] { compilation.EmitToImageReference() }, options: TestOptions.ReleaseDll.WithMetadataImportOptions(MetadataImportOptions.All));
+            c1 = compilation.GetTypeByMetadataName("C1");
+            m1 = c1.GetMember<MethodSymbol>("M1");
+            Assert.Equal("void C1.M1<T>(T! x, T?[]! y, System.Action<T!>! z, System.Action<T?[]?>?[]? u)", m1.ToTestDisplayString(includeNonNullable: true));
         }
 
         [Fact]

src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs

@@ -348,6 +348,7 @@ public void WarningLevel_2()
                         case ErrorCode.WRN_SyncAndAsyncEntryPoints:
                         case ErrorCode.WRN_ParameterIsStaticClass:
                         case ErrorCode.WRN_ReturnTypeIsStaticClass:
+                        case ErrorCode.WRN_PartialMethodTypeDifference:
                             // These are the warnings introduced with the warning "wave" shipped with dotnet 5 and C# 9.
                             Assert.Equal(5, ErrorFacts.GetWarningLevel(errorCode));
                             break;
@@ -407,6 +408,7 @@ public void NullableWarnings()
                     ErrorCode.WRN_ParameterIsStaticClass,
                     ErrorCode.WRN_ReturnTypeIsStaticClass,
                     ErrorCode.WRN_RecordNamedDisallowed,
+                    ErrorCode.WRN_PartialMethodTypeDifference,
                 };
 
                 Assert.Contains(error, nullableUnrelatedWarnings);

src/Test/Utilities/Portable/Diagnostics/DiagnosticDescription.cs

@@ -378,8 +378,10 @@ public override string ToString()
                 sb.Append('"');
             }
 
-            sb.Append(", isSuppressed: ");
-            sb.Append(_isSuppressed ? "true" : "false");
+            if (_isSuppressed)
+            {
+                sb.Append(", isSuppressed: true");
+            }
 
             sb.Append(")");