Fix #272

src/analysis/auto_ref_assignment.d

@@ -0,0 +1,128 @@
+//          Copyright Brian Schott (Hackerpilot) 2015.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+module analysis.auto_ref_assignment;
+
+import dparse.lexer;
+import dparse.ast;
+import analysis.base;
+
+/**
+ * Checks for assignment to auto-ref function parameters.
+ */
+class AutoRefAssignmentCheck : BaseAnalyzer
+{
+	///
+	this(string fileName)
+	{
+		super(fileName, null);
+	}
+
+	override void visit(const FunctionDeclaration func)
+	{
+		if (func.parameters is null || func.parameters.parameters.length == 0)
+			return;
+		pushScope();
+		scope (exit)
+			popScope();
+		func.accept(this);
+	}
+
+	override void visit(const Parameter param)
+	{
+		import std.algorithm.searching : canFind;
+
+		immutable bool isAuto = param.parameterAttributes.canFind(cast(ubyte) tok!"auto");
+		immutable bool isRef = param.parameterAttributes.canFind(cast(ubyte) tok!"ref");
+		if (!isAuto || !isRef)
+			return;
+		addSymbol(param.name.text);
+	}
+
+	override void visit(const AssignExpression assign)
+	{
+		if (assign.operator == tok!"" || scopes.length == 0)
+			return;
+		interest++;
+		assign.ternaryExpression.accept(this);
+		interest--;
+	}
+
+	override void visit(const IdentifierOrTemplateInstance ioti)
+	{
+		import std.algorithm.searching : canFind;
+
+		if (ioti.identifier == tok!"" || interest <= 0)
+			return;
+		if (scopes[$ - 1].canFind(ioti.identifier.text))
+			addErrorMessage(ioti.identifier.line, ioti.identifier.column, KEY,
+				"Assignment to auto-ref function parameter");
+	}
+
+	override void visit(const IdentifierChain ic)
+	{
+		import std.algorithm.searching : canFind;
+
+		if (ic.identifiers.length == 0 || interest <= 0)
+			return;
+		if (scopes[$ - 1].canFind(ic.identifiers[0].text))
+			addErrorMessage(ic.identifiers[0].line, ic.identifiers[0].column, KEY,
+				MESSAGE);
+	}
+
+	alias visit = BaseAnalyzer.visit;
+
+private:
+
+	enum string MESSAGE = "Assignment to auto-ref function parameter";
+	enum string KEY = "dscanner.suspicious.auto_ref_assignment";
+
+	invariant
+	{
+		assert(interest >= 0);
+	}
+
+	int interest;
+
+	void addSymbol(string symbolName)
+	{
+		scopes[$ - 1] ~= symbolName;
+	}
+
+	void pushScope()
+	{
+		scopes.length++;
+	}
+
+	void popScope()
+	{
+		scopes = scopes[0 .. $ - 1];
+	}
+
+	string[][] scopes;
+}
+
+unittest
+{
+	import std.stdio : stderr;
+	import std.format : format;
+	import analysis.config : StaticAnalysisConfig;
+	import analysis.helpers : assertAnalyzerWarnings;
+
+	StaticAnalysisConfig sac;
+	sac.auto_ref_assignment_check = true;
+	assertAnalyzerWarnings(q{
+		int doStuff(T)(auto ref int a)
+		{
+			a = 10; // [warn]: %s
+		}
+
+		int doStuff(T)(ref int a)
+		{
+			a = 10;
+		}
+	}c.format(AutoRefAssignmentCheck.MESSAGE), sac);
+	stderr.writeln("Unittest for AutoRefAssignmentCheck passed.");
+}

src/analysis/config.d

@@ -101,4 +101,7 @@ struct StaticAnalysisConfig
 
 	@INI("Checks for lines longer than 120 characters")
 	bool long_line_check;
+
+	@INI("Checks for assignment to auto-ref function parameters")
+	bool auto_ref_assignment_check;
 }

src/analysis/run.d

@@ -52,6 +52,7 @@ import analysis.redundant_parens;
 import analysis.mismatched_args;
 import analysis.label_var_same_name_check;
 import analysis.line_length;
+import analysis.auto_ref_assignment;
 
 import dsymbol.string_interning : internString;
 import dsymbol.scope_;
@@ -260,6 +261,8 @@ MessageSet analyze(string fileName, const Module m,
 		checks ~= new UnusedVariableCheck(fileName, moduleScope);
 	if (analysisConfig.long_line_check)
 		checks ~= new LineLengthCheck(fileName, tokens);
+	if (analysisConfig.auto_ref_assignment_check)
+		checks ~= new AutoRefAssignmentCheck(fileName);
 	version (none)
 		if (analysisConfig.redundant_if_check)
 			checks ~= new IfStatementCheck(fileName, moduleScope);