Refix MSVC Debug crash

Author: a3d4

libsolutil/Visitor.h

@@ -56,6 +56,17 @@ struct VisitorFallback<R> { template<typename T> R operator()(T&&) const { retur
 template<>
 struct VisitorFallback<> { template<typename T> void operator()(T&&) const {} };
 
-template <typename... Visitors> struct GenericVisitor: Visitors... { using Visitors::operator()...; };
+// MSVC. Empty base class optimization does not happen in some scenarios.
+// Enforcing it with __declspec(empty_bases) avoids MSVC Debug test crash
+// (Run-Time Check Failure #2 - Stack around the variable '....' was corrupted).
+// See https://docs.microsoft.com/en-us/cpp/cpp/empty-bases,
+//     https://developercommunity.visualstudio.com/t/10005513.
+#if defined(_MSC_VER)
+#define SOLC_EMPTY_BASES __declspec(empty_bases)
+#else
+#define SOLC_EMPTY_BASES
+#endif
+
+template <typename... Visitors> struct SOLC_EMPTY_BASES GenericVisitor: Visitors... { using Visitors::operator()...; };
 template <typename... Visitors> GenericVisitor(Visitors...) -> GenericVisitor<Visitors...>;
 }

libyul/optimiser/StructuralSimplifier.cpp

@@ -93,32 +93,27 @@ void StructuralSimplifier::operator()(Block& _block)
 
 void StructuralSimplifier::simplify(std::vector<yul::Statement>& _statements)
 {
-	// Explicit local variables ifLambda, switchLambda, forLoopLambda are created to avoid MSVC C++17 Debug test crash
-	// (Run-Time Check Failure #2 - Stack around the variable '....' was corrupted).
-	// As soon as the issue is fixed, this workaround can be removed.
-	auto ifLambda = [&](If& _ifStmt) -> OptionalStatements
-	{
-		if (expressionAlwaysTrue(*_ifStmt.condition))
-			return {std::move(_ifStmt.body.statements)};
-		else if (expressionAlwaysFalse(*_ifStmt.condition))
-			return {vector<Statement>{}};
-		return {};
-	};
-	auto switchLambda = [&](Switch& _switchStmt) -> OptionalStatements
-	{
-		if (std::optional<u256> const constExprVal = hasLiteralValue(*_switchStmt.expression))
-			return replaceConstArgSwitch(_switchStmt, constExprVal.value());
-		return {};
-	};
-	auto forLoopLambda = [&](ForLoop& _forLoop) -> OptionalStatements
-	{
-		if (expressionAlwaysFalse(*_forLoop.condition))
-			return {std::move(_forLoop.pre.statements)};
-		return {};
+	util::GenericVisitor visitor{
+		util::VisitorFallback<OptionalStatements>{},
+		[&](If& _ifStmt) -> OptionalStatements {
+			if (expressionAlwaysTrue(*_ifStmt.condition))
+				return {std::move(_ifStmt.body.statements)};
+			else if (expressionAlwaysFalse(*_ifStmt.condition))
+				return {vector<Statement>{}};
+			return {};
+		},
+		[&](Switch& _switchStmt) -> OptionalStatements {
+			if (std::optional<u256> const constExprVal = hasLiteralValue(*_switchStmt.expression))
+				return replaceConstArgSwitch(_switchStmt, constExprVal.value());
+			return {};
+		},
+		[&](ForLoop& _forLoop) -> OptionalStatements {
+			if (expressionAlwaysFalse(*_forLoop.condition))
+				return {std::move(_forLoop.pre.statements)};
+			return {};
+		}
 	};
 
-	util::GenericVisitor visitor{util::VisitorFallback<OptionalStatements>{}, ifLambda, switchLambda, forLoopLambda};
-
 	util::iterateReplacing(
 		_statements,
 		[&](Statement& _stmt) -> OptionalStatements