Address feedback: split binding/parsing logic using partial files rat…

…her than new method spec types

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs

@@ -52,18 +52,16 @@ private static void Execute(CompilationData compilationData, ImmutableArray<Bind
                 return;
             }
 
-            if (compilationData?.LanguageVersionIsSupported != true)
+            if (compilationData?.LanguageVersionIsSupported is not true)
             {
                 context.ReportDiagnostic(Diagnostic.Create(Parser.Diagnostics.LanguageVersionNotSupported, location: null));
                 return;
             }
 
             Parser parser = new(context, compilationData.TypeSymbols!, inputCalls);
-            SourceGenSpec? spec = parser.GetSourceGenerationSpec();
-
-            if (spec?.HasRootMethods() is true)
+            if (parser.GetSourceGenerationSpec() is SourceGenerationSpec { } spec)
             {
-                Emitter emitter = new(context, spec!);
+                Emitter emitter = new(context, spec);
                 emitter.Emit();
             }
         }