Fix memory leaks for return values and some out params. (dotnet/runti…

…melab#1200)

Fix some memory leaks we had where we didn't generate code to free native resources for out parameters that use custom native type marshalling or all return values.

Also set a flag in the csproj that enables a nice debugging innerloop option for roslyn components in the csproj settings (in our case running the generator on the integration tests)

Commit migrated from dotnet/runtimelab@b11a26a

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/DllImportGenerator.csproj

@@ -10,6 +10,7 @@
     <LangVersion>Preview</LangVersion>
     <Nullable>enable</Nullable>
     <RootNamespace>Microsoft.Interop</RootNamespace>
+    <IsRoslynComponent>true</IsRoslynComponent>
   </PropertyGroup>
 
   <PropertyGroup>

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/Marshalling/CustomNativeTypeMarshaller.cs

@@ -231,7 +231,7 @@ public IEnumerable<StatementSyntax> Generate(TypePositionInfo info, StubCodeCont
                     }
                     break;
                 case StubCodeContext.Stage.Cleanup:
-                    if (info.RefKind != RefKind.Out && _hasFreeNative)
+                    if (_hasFreeNative)
                     {
                         // <marshalerIdentifier>.FreeNative();
                         yield return ExpressionStatement(

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/Marshalling/SafeHandleMarshaller.cs

@@ -228,7 +228,7 @@ public IEnumerable<StatementSyntax> Generate(TypePositionInfo info, StubCodeCont
                     }
                     break;
                 case StubCodeContext.Stage.Cleanup:
-                    if (!info.IsByRef || info.RefKind == RefKind.In)
+                    if (!info.IsManagedReturnPosition && (!info.IsByRef || info.RefKind == RefKind.In))
                     {
                         yield return IfStatement(
                             IdentifierName(addRefdIdentifier),

src/libraries/System.Runtime.InteropServices/gen/DllImportGenerator/StubCodeGenerator.cs

@@ -197,7 +197,7 @@ public BlockSyntax GenerateSyntax()
                 int initialCount = statements.Count;
                 this.CurrentStage = stage;
 
-                if (!invokeReturnsVoid && (stage == Stage.Setup || stage == Stage.Unmarshal || stage == Stage.GuaranteedUnmarshal))
+                if (!invokeReturnsVoid && (stage is Stage.Setup or Stage.Unmarshal or Stage.GuaranteedUnmarshal or Stage.Cleanup))
                 {
                     // Handle setup and unmarshalling for return
                     var retStatements = retMarshaller.Generator.Generate(retMarshaller.TypeInfo, this);