ilya-biryukov created this revision.
ilya-biryukov added a reviewer: sammccall.
Herald added subscribers: ioeric, jkorous-apple, klimek.
r322838 changed semantics for llvm::Optional that removes the
guarantee of setting the value to empty after move.
This change creates a wrapper around Optional that gives this
guarantee, it is useful for code dealing with empty values that could
be moved.
Repository:
rCTE Clang Tools Extra
https://reviews.llvm.org/D42525
Files:
clangd/Function.h
Index: clangd/Function.h
===================================================================
--- clangd/Function.h
+++ clangd/Function.h
@@ -138,6 +138,33 @@
}
namespace detail {
+/// Optional-like type that sets its value to llvm::None when it was moved
+/// constructed from.
+template <class T> class CleaningOptional {
+public:
+ static_assert(std::is_same<typename std::decay<T>::type, T>::value,
+ "Implementation currently only supports decayed types");
+
+ CleaningOptional(T Value) : Value(std::move(Value)) {}
+
+ CleaningOptional(CleaningOptional &&Other) : Value(std::move(Other.Value)) {
+ Other.Value = llvm::None;
+ }
+
+ CleaningOptional &operator=(CleaningOptional &&Other) {
+ Value = std::move(Other.Value);
+ Other.Value = llvm::None;
+ }
+
+ explicit operator bool() const { return static_cast<bool>(Value); }
+
+ T &operator*() { return *Value; }
+ const T &operator*() const { return *Value; }
+
+private:
+ llvm::Optional<T> Value;
+};
+
/// Runs provided callback in destructor. Use onScopeExit helper function to
/// create this object.
template <class Func> struct ScopeExitGuard {
@@ -159,7 +186,7 @@
ScopeExitGuard &operator=(ScopeExitGuard &&Other) = default;
private:
- llvm::Optional<Func> F;
+ CleaningOptional<Func> F;
};
} // namespace detail
Index: clangd/Function.h
===================================================================
--- clangd/Function.h
+++ clangd/Function.h
@@ -138,6 +138,33 @@
}
namespace detail {
+/// Optional-like type that sets its value to llvm::None when it was moved
+/// constructed from.
+template <class T> class CleaningOptional {
+public:
+ static_assert(std::is_same<typename std::decay<T>::type, T>::value,
+ "Implementation currently only supports decayed types");
+
+ CleaningOptional(T Value) : Value(std::move(Value)) {}
+
+ CleaningOptional(CleaningOptional &&Other) : Value(std::move(Other.Value)) {
+ Other.Value = llvm::None;
+ }
+
+ CleaningOptional &operator=(CleaningOptional &&Other) {
+ Value = std::move(Other.Value);
+ Other.Value = llvm::None;
+ }
+
+ explicit operator bool() const { return static_cast<bool>(Value); }
+
+ T &operator*() { return *Value; }
+ const T &operator*() const { return *Value; }
+
+private:
+ llvm::Optional<T> Value;
+};
+
/// Runs provided callback in destructor. Use onScopeExit helper function to
/// create this object.
template <class Func> struct ScopeExitGuard {
@@ -159,7 +186,7 @@
ScopeExitGuard &operator=(ScopeExitGuard &&Other) = default;
private:
- llvm::Optional<Func> F;
+ CleaningOptional<Func> F;
};
} // namespace detail
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