Add NES013 analyzer diagnostic for throw statements

src/dotnes.analyzers.tests/NESAnalyzerTests.cs

@@ -992,4 +992,41 @@ static class Config
         var expected = Diagnostic(NESAnalyzer.NES012).WithLocation(0).WithArguments("Speed");
         await VerifyLibraryAsync(test, expected);
     }
+
+    // ==================== NES013: throw is not supported ====================
+
+    [Fact]
+    public async Task NES013_ThrowStatement_Diagnostic()
+    {
+        var test = """
+            {|#0:throw null;|}
+            while (true) ;
+            """;
+
+        var expected = Diagnostic(NESAnalyzer.NES013).WithLocation(0);
+        await VerifyAsync(test, expected);
+    }
+
+    [Fact]
+    public async Task NES013_ThrowExpression_Diagnostic()
+    {
+        var test = """
+            static byte GetValue(bool b) => b ? (byte)1 : {|#0:throw null|};
+            while (true) ;
+            """;
+
+        var expected = Diagnostic(NESAnalyzer.NES013).WithLocation(0);
+        await VerifyAsync(test, expected);
+    }
+
+    [Fact]
+    public async Task NES013_NoThrow_NoDiagnostic()
+    {
+        var test = """
+            byte x = 0;
+            while (true) ;
+            """;
+
+        await VerifyAsync(test);
+    }
 }

src/dotnes.analyzers/AnalyzerReleases.Unshipped.md

@@ -1,2 +1,8 @@
 ; Unshipped analyzer release
 ; https://github.com/dotnet/roslyn-analyzers/blob/main/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md
+
+### New Rules
+
+Rule ID | Category | Severity | Notes
+--------|----------|----------|-------
+NES013 | NES | Error | throw is not supported

src/dotnes.analyzers/NESAnalyzer.cs

@@ -22,6 +22,7 @@ public class NESAnalyzer : DiagnosticAnalyzer
     public const string NES010 = nameof(NES010);
     public const string NES011 = nameof(NES011);
     public const string NES012 = nameof(NES012);
+    public const string NES013 = nameof(NES013);
 
     const string Category = "NES";
 
@@ -133,9 +134,18 @@ public class NESAnalyzer : DiagnosticAnalyzer
         isEnabledByDefault: true,
         description: "Properties generate hidden getter/setter methods that the NES transpiler cannot handle. Use public fields instead.");
 
+    static readonly DiagnosticDescriptor NES013Rule = new(
+        NES013,
+        "throw is not supported",
+        "throw is not supported on the NES. The 6502 CPU has no exception handling mechanism.",
+        Category,
+        DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "The NES 6502 CPU has no exception handling mechanism. throw statements and throw expressions are not supported.");
+
     public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics =>
         ImmutableArray.Create(NES001Rule, NES002Rule, NES003Rule, NES004Rule, NES005Rule, NES006Rule,
-            NES007Rule, NES008Rule, NES009Rule, NES010Rule, NES011Rule, NES012Rule);
+            NES007Rule, NES008Rule, NES009Rule, NES010Rule, NES011Rule, NES012Rule, NES013Rule);
 
     public override void Initialize(AnalysisContext context)
     {
@@ -160,6 +170,7 @@ public override void Initialize(AnalysisContext context)
         context.RegisterSyntaxNodeAction(AnalyzeForEach, SyntaxKind.ForEachStatement);
         context.RegisterSyntaxNodeAction(AnalyzeTryCatchFinally, SyntaxKind.TryStatement);
         context.RegisterSyntaxNodeAction(AnalyzePropertyDeclaration, SyntaxKind.PropertyDeclaration);
+        context.RegisterSyntaxNodeAction(AnalyzeThrowStatement, SyntaxKind.ThrowStatement, SyntaxKind.ThrowExpression);
     }
 
     static void AnalyzeClassDeclaration(SyntaxNodeAnalysisContext context)
@@ -541,6 +552,11 @@ static void AnalyzePropertyDeclaration(SyntaxNodeAnalysisContext context)
         context.ReportDiagnostic(Diagnostic.Create(NES012Rule, property.Identifier.GetLocation(), property.Identifier.Text));
     }
 
+    static void AnalyzeThrowStatement(SyntaxNodeAnalysisContext context)
+    {
+        context.ReportDiagnostic(Diagnostic.Create(NES013Rule, context.Node.GetLocation()));
+    }
+
     static bool IsSupportedType(ITypeSymbol type)
     {
         // byte, sbyte, ushort are supported