private static Formatter?GetFormatter( Compilation compilation, AttributedMembers attrMembers, SerializerTypes types, ITypeSymbol toFormatType, Location?location, ImmutableArray <AttributeSyntax> attrs, ref ImmutableArray <Diagnostic> diags ) { var formatter = Utils.GetMethodFromAttribute( attrMembers, "FormatterType", Diagnostics.FormatterTypeSpecifiedMultipleTimes, "FormatterMethodName", Diagnostics.FormatterMethodNameSpecifiedMultipleTimes, Diagnostics.FormatterBothMustBeSet, location, attrs, ref diags ); if (formatter == null) { return(null); } var(type, mtd) = formatter.Value; var formatterMtd = Utils.GetMethod(type, mtd, location, ref diags); if (formatterMtd == null) { return(null); } if (formatterMtd.IsGenericMethod) { var diag = Diagnostics.MethodCannotBeGeneric(location, formatterMtd); diags = diags.Add(diag); return(null); } var accessible = formatterMtd.IsAccessible(attrMembers); if (!accessible) { var diag = Diagnostics.MethodNotPublicOrInternal(location, formatterMtd); diags = diags.Add(diag); return(null); } if (!formatterMtd.IsStatic) { var diag = Diagnostics.MethodNotStatic(location, formatterMtd); diags = diags.Add(diag); return(null); } if (!formatterMtd.ReturnType.Equals(types.BuiltIn.Bool, SymbolEqualityComparer.Default)) { var diag = Diagnostics.MethodMustReturnBool(location, formatterMtd); diags = diags.Add(diag); return(null); } var formatterParams = formatterMtd.Parameters; if (formatterParams.Length != 3) { var diag = Diagnostics.BadFormatterParameters(location, formatterMtd, toFormatType); diags = diags.Add(diag); return(null); } var p0 = formatterParams[0]; if (!p0.IsNormalParameterOfType(compilation, toFormatType)) { var diag = Diagnostics.BadFormatterParameters(location, formatterMtd, toFormatType); diags = diags.Add(diag); return(null); } var p1 = formatterParams[1]; if (!p1.IsInWriteContext(types.OurTypes)) { var diag = Diagnostics.BadFormatterParameters(location, formatterMtd, toFormatType); diags = diags.Add(diag); return(null); } var p2 = formatterParams[2]; if (!p2.IsNormalParameterOfType(compilation, types.Framework.IBufferWriterOfChar)) { var diag = Diagnostics.BadFormatterParameters(location, formatterMtd, toFormatType); diags = diags.Add(diag); return(null); } return(new Formatter(formatterMtd, toFormatType)); }