add a check for the auto functions without return statement

README.md

@@ -116,6 +116,7 @@ Note that the "--skipTests" option is the equivalent of changing each
 * Lines longer than 120 characters.
 * Incorrect infinite range definitions.
 * Some assertions that check conditions that will always be true.
+* Auto functions without return statement. The compiler doesn't see an omission and it infers 'void' as return type.
 
 #### Wishlist
 

src/analysis/auto_function.d

@@ -0,0 +1,87 @@
+//          Copyright Basile Burg 2016.
+// 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_function;
+
+import analysis.base;
+import analysis.helpers;
+import dparse.ast;
+import dparse.lexer;
+
+import std.stdio;
+import std.algorithm.searching : any;
+
+/**
+ * Checks for auto functions without return statement.
+ *
+ * Auto function without return statement can be an omission and are not
+ * detected by the compiler. However sometimes they can be used as a trick
+ * to infer attributes.
+ */
+final class AutoFunctionChecker : BaseAnalyzer
+{
+
+private:
+
+	enum string KEY = "dscanner.suspicious.missing_return";
+	enum string MESSAGE = "Auto function without return statement, prefer an explicit void";
+
+	bool[] _returns;
+
+public:
+
+	alias visit = BaseAnalyzer.visit;
+
+	///
+	this(string fileName, bool skipTests = false)
+	{
+		super(fileName, null, skipTests);
+	}
+
+	override void visit(const FunctionDeclaration decl)
+	{
+		_returns.length += 1;
+		scope(exit) _returns.length -= 1;
+		_returns[$-1] = false;
+
+		const bool autoFun = decl.storageClasses
+			.any!(a => a.token.type == tok!"auto");
+
+		decl.accept(this);
+
+		if (autoFun && !_returns[$-1])
+			addErrorMessage(decl.name.line, decl.name.column, KEY, MESSAGE);
+	}
+
+	override void visit(const ReturnStatement rst)
+	{
+		if (_returns.length)
+			_returns[$-1] = true;
+		rst.accept(this);
+	}
+}
+
+unittest
+{
+	import std.stdio : stderr;
+	import std.format : format;
+	import analysis.config : StaticAnalysisConfig, Check;
+	import analysis.helpers : assertAnalyzerWarnings;
+
+	StaticAnalysisConfig sac;
+	sac.auto_function_check = Check.enabled;
+	assertAnalyzerWarnings(q{
+		auto ref doStuff(){} // [warn]: %s
+        auto doStuff(){} // [warn]: %s
+        int doStuff(){auto doStuff(){}} // [warn]: %s
+        auto doStuff(){return 0;}
+        int doStuff(){/*error but not the aim*/}
+	}c.format(
+        AutoFunctionChecker.MESSAGE,
+        AutoFunctionChecker.MESSAGE,
+        AutoFunctionChecker.MESSAGE,
+    ), sac);
+	stderr.writeln("Unittest for AutoFunctionChecker passed.");
+}

src/analysis/config.d

@@ -140,8 +140,11 @@ struct StaticAnalysisConfig
 	string alias_syntax_check = Check.disabled;
 
 	@INI("Checks for else if that should be else static if")
-    string static_if_else_check = Check.disabled;
+	string static_if_else_check = Check.disabled;
 
 	@INI("Check for unclear lambda syntax")
 	string lambda_return_check = Check.disabled;
+
+	@INI("Check for auto function without return statement")
+	string auto_function_check = Check.disabled;
 }

src/analysis/run.d

@@ -59,6 +59,7 @@ import analysis.useless_assert;
 import analysis.alias_syntax_check;
 import analysis.static_if_else;
 import analysis.lambda_return_check;
+import analysis.auto_function;
 
 import dsymbol.string_interning : internString;
 import dsymbol.scope_;
@@ -354,6 +355,10 @@ MessageSet analyze(string fileName, const Module m, const StaticAnalysisConfig a
 		checks ~= new LambdaReturnCheck(fileName,
 		analysisConfig.lambda_return_check == Check.skipTests && !ut);
 
+	if (analysisConfig.auto_function_check != Check.disabled)
+		checks ~= new AutoFunctionChecker(fileName,
+		analysisConfig.auto_function_check == Check.skipTests && !ut);
+
 	version (none)
 		if (analysisConfig.redundant_if_check != Check.disabled)
 			checks ~= new IfStatementCheck(fileName, moduleScope,