FailFast instead of throw from non-HRESULT returning CCW methods

Closes #830

src/Microsoft.Windows.CsWin32/FastSyntaxFactory.cs

@@ -134,6 +134,8 @@ internal static ForStatementSyntax ForStatement(VariableDeclarationSyntax? decla
 
     internal static AttributeTargetSpecifierSyntax AttributeTargetSpecifier(SyntaxToken identifier) => SyntaxFactory.AttributeTargetSpecifier(identifier, TokenWithSpace(SyntaxKind.ColonToken));
 
+    internal static ThrowStatementSyntax ThrowStatement() => SyntaxFactory.ThrowStatement(default, Token(SyntaxKind.ThrowKeyword), null, Semicolon);
+
     internal static ThrowStatementSyntax ThrowStatement(ExpressionSyntax expression) => SyntaxFactory.ThrowStatement(Token(TriviaList(), SyntaxKind.ThrowKeyword, TriviaList(Space)), expression, Semicolon);
 
     internal static ThrowExpressionSyntax ThrowExpression(ExpressionSyntax expression) => SyntaxFactory.ThrowExpression(Token(TriviaList(), SyntaxKind.ThrowKeyword, TriviaList(Space)), expression);

src/Microsoft.Windows.CsWin32/Generator.Com.cs

@@ -425,20 +425,35 @@ void AddCcwThunk(params StatementSyntax[] thunkInvokeAndReturn)
                     //// hr.ThrowOnFailure();
                     : ExpressionStatement(InvocationExpression(MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, hrLocal, HRThrowOnFailureMethodName)));
 
-                //// catch (Exception ex) { return (HRESULT)ex.HResult; }
                 IdentifierNameSyntax exLocal = IdentifierName("ex");
-                CatchClauseSyntax catchClause = CatchClause(CatchDeclaration(IdentifierName(nameof(Exception)).WithTrailingTrivia(Space), exLocal.Identifier), null, Block().AddStatements(
-                    ReturnStatement(CastExpression(HresultTypeSyntax, MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, exLocal, IdentifierName(nameof(Exception.HResult)))))));
+                BlockSyntax catchBlock = Block();
+                if (hrReturnType)
+                {
+                    //// return (HRESULT)ex.HResult;
+                    catchBlock = catchBlock.AddStatements(ReturnStatement(CastExpression(HresultTypeSyntax, MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, exLocal, IdentifierName(nameof(Exception.HResult))))));
+                }
+                else
+                {
+                    //// Environment.FailFast("COM object threw an exception from a non-HRESULT returning method.", ex);
+                    //// throw;
+                    catchBlock = catchBlock.AddStatements(
+                        ExpressionStatement(InvocationExpression(
+                            MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression, ParseName("global::System.Environment"), IdentifierName(nameof(Environment.FailFast))),
+                            ArgumentList().AddArguments(
+                                Argument(LiteralExpression(SyntaxKind.StringLiteralExpression, Literal("COM object threw an exception from a non-HRESULT returning method."))),
+                                Argument(exLocal)))),
+                        ThrowStatement());
+                }
+
+                //// catch (Exception ex) {
+                CatchClauseSyntax catchClause = CatchClause(CatchDeclaration(IdentifierName(nameof(Exception)).WithTrailingTrivia(Space), exLocal.Identifier), null, catchBlock);
 
                 BlockSyntax tryBlock = Block().AddStatements(
                     hrDecl,
                     ifNullReturnStatement).AddStatements(thunkInvokeAndReturn);
 
-                BlockSyntax ccwBody = hrReturnType
-                    //// try { ... } catch { ... }
-                    ? Block().AddStatements(TryStatement(tryBlock, new SyntaxList<CatchClauseSyntax>(catchClause), null))
-                    //// { .... } // any exception is thrown back to native code.
-                    : tryBlock;
+                //// try { ... } catch { ... }
+                BlockSyntax ccwBody = Block().AddStatements(TryStatement(tryBlock, new SyntaxList<CatchClauseSyntax>(catchClause), null));
 
                 //// [UnmanagedCallersOnly(CallConvs = new[] { typeof(CallConvStdcall) })]
                 //// private static HRESULT Clone(IEnumEventObject* @this, IEnumEventObject** ppInterface)

src/Microsoft.Windows.CsWin32/Generator.WhitespaceRewriter.cs

@@ -206,6 +206,8 @@ internal WhitespaceRewriter()
 
         public override SyntaxNode? VisitTryStatement(TryStatementSyntax node) => base.VisitTryStatement(this.WithIndentingTrivia(node));
 
+        public override SyntaxNode? VisitThrowStatement(ThrowStatementSyntax node) => base.VisitThrowStatement(this.WithIndentingTrivia(node));
+
         public override SyntaxNode? VisitCatchClause(CatchClauseSyntax node) => base.VisitCatchClause(this.WithIndentingTrivia(node));
 
         public override SyntaxNode? VisitFinallyClause(FinallyClauseSyntax node) => base.VisitFinallyClause(this.WithIndentingTrivia(node));

test/Microsoft.Windows.CsWin32.Tests/COMTests.cs

@@ -294,6 +294,22 @@ public void InterestingComInterfaces(
         this.AssertNoDiagnostics();
     }
 
+    [Fact]
+    public void EnvironmentFailFast()
+    {
+        this.compilation = this.starterCompilations["net7.0"];
+        this.generator = this.CreateGenerator(DefaultTestGeneratorOptions with { AllowMarshaling = false });
+
+        // Emit something into the Environment namespace, to invite collisions.
+        Assert.True(this.generator.TryGenerate("ENCLAVE_IDENTITY", CancellationToken.None));
+
+        // Emit the interface that can require Environment.FailFast.
+        Assert.True(this.generator.TryGenerate("ITypeInfo", CancellationToken.None));
+
+        this.CollectGeneratedCode(this.generator);
+        this.AssertNoDiagnostics();
+    }
+
     [Fact]
     public void ComOutPtrTypedAsOutObject()
     {