private static Parser?GetParser( Compilation compilation, AttributedMembers attrMembers, DeserializerTypes types, ITypeSymbol toParseType, Location?location, ImmutableArray <AttributeSyntax> attrs, ref ImmutableArray <Diagnostic> diags ) { var parser = Utils.GetMethodFromAttribute( attrMembers, "ParserType", Diagnostics.ParserTypeSpecifiedMultipleTimes, "ParserMethodName", Diagnostics.ParserMethodNameSpecifiedMultipleTimes, Diagnostics.ParserBothMustBeSet, location, attrs, ref diags ); if (parser == null) { return(null); } var(type, name) = parser.Value; var parserMtd = Utils.GetMethod(type, name, location, ref diags); if (parserMtd == null) { return(null); } var methodReturnType = parserMtd.ReturnType; if (methodReturnType.SpecialType != SpecialType.System_Boolean) { var diag = Diagnostics.MethodMustReturnBool(location, parserMtd); diags = diags.Add(diag); return(null); } if (!parserMtd.IsStatic) { var diag = Diagnostics.MethodNotStatic(location, parserMtd); diags = diags.Add(diag); return(null); } var accessible = parserMtd.IsAccessible(attrMembers); if (!accessible) { var diag = Diagnostics.MethodNotPublicOrInternal(location, parserMtd); diags = diags.Add(diag); return(null); } var ps = parserMtd.Parameters; if (ps.Length != 3) { var diag = Diagnostics.BadParserParameters(location, parserMtd); diags = diags.Add(diag); return(null); } // Parameters // * ReadOnlySpan(char) // * in ReadContext, // * out assignable to outputType var p0 = ps[0]; if (!p0.IsNormalParameterOfType(compilation, types.Framework.ReadOnlySpanOfChar)) { var diag = Diagnostics.BadParserParameters(location, parserMtd); diags = diags.Add(diag); return(null); } var p1 = ps[1]; if (!p1.IsInReadContext(types.OurTypes)) { var diag = Diagnostics.BadParserParameters(location, parserMtd); diags = diags.Add(diag); return(null); } var p2 = ps[2]; if (p2.RefKind != RefKind.Out) { var diag = Diagnostics.BadParserParameters(location, parserMtd); diags = diags.Add(diag); return(null); } var conversion = compilation.ClassifyConversion(p2.Type, toParseType); var canConvert = conversion.IsImplicit || conversion.IsIdentity; if (!canConvert) { var diag = Diagnostics.BadParserParameters(location, parserMtd); diags = diags.Add(diag); return(null); } return(new Parser(parserMtd, p2.Type)); }