store parameter storage classes in DSymbols

dsymbol/src/dsymbol/conversion/first.d

@@ -964,6 +964,39 @@ private:
 				if (p.type !is null)
 					addTypeToLookups(parameter.typeLookups, p.type);
 				parameter.parent = currentSymbol;
+				foreach (const attribute; p.parameterAttributes)
+				{
+					switch (attribute.idType)
+					{
+					case tok!"ref":
+						if (!parameter.acSymbol.parameterIsAutoRef)
+							parameter.acSymbol.parameterIsRef = true;
+						break;
+					case tok!"auto":
+						// assume this is `auto ref`, since otherwise `auto` is
+						// not a valid parameter attribute.
+						if (!parameter.acSymbol.parameterIsRef)
+							parameter.acSymbol.parameterIsAutoRef = true;
+						break;
+					case tok!"scope":
+						parameter.acSymbol.parameterIsScope = true;
+						break;
+					case tok!"return":
+						parameter.acSymbol.parameterIsReturn = true;
+						break;
+					case tok!"lazy":
+						parameter.acSymbol.parameterIsLazy = true;
+						break;
+					case tok!"out":
+						parameter.acSymbol.parameterIsOut = true;
+						break;
+					case tok!"in":
+						parameter.acSymbol.parameterIsIn = true;
+						break;
+					default:
+						break;
+					}
+				}
 				currentSymbol.acSymbol.argNames.insert(parameter.acSymbol.name);
 
 				currentSymbol.acSymbol.functionParameters ~= parameter.acSymbol;

dsymbol/src/dsymbol/symbol.d

@@ -434,11 +434,41 @@ struct DSymbol
 	 * If true, this symbol owns its type and will free it on destruction
 	 */
 	// dfmt off
-	mixin(bitfields!(bool, "ownType", 1,
+	mixin(bitfields!(
+		bool, "ownType", 1,
 		bool, "skipOver", 1,
-		ubyte, "", 6));
+		bool, "_flag0", 1, // planned: const/immutable/shared/inout for types and parameters
+		bool, "_flag1", 1,
+		bool, "_flag2", 1,
+		bool, "_flag3", 1,
+		bool, "_flag4", 1,
+		bool, "_flag5", 1,
+		bool, "_flag6", 1,
+		bool, "_flag7", 1,
+		bool, "_flag8", 1,
+		bool, "_flag9", 1,
+		bool, "_flag10", 1,
+		uint, "", 3,
+	));
 	// dfmt on
 
+	/// Only valid for parameters: the parameter has storage class `ref` (not `auto ref`)
+	alias parameterIsRef = _flag4;
+	/// Only valid for parameters: the parameter has storage class `auto ref` (not `ref`)
+	alias parameterIsAutoRef = _flag5;
+	// TODO: maybe parameterIsScope and parameterIsReturn need to be differentiated for `scope return` and `return scope`?
+	// unsure about the needed semantics here.
+	/// Only valid for parameters: the parameter has storage class `scope`
+	alias parameterIsScope = _flag6;
+	/// Only valid for parameters: the parameter has storage class `return`
+	alias parameterIsReturn = _flag7;
+	/// Only valid for parameters: the parameter has storage class `lazy`
+	alias parameterIsLazy = _flag8;
+	/// Only valid for parameters: the parameter has storage class `out`
+	alias parameterIsOut = _flag9;
+	/// Only valid for parameters: the parameter has storage class `in`
+	alias parameterIsIn = _flag10;
+
 	deprecated bool isPointer()
 	{
 		return qualifier == SymbolQualifier.pointer;