[llvm] 4cae622 - [ADT] function_ref's constructor is unavailable if the argument is not callable.
Sam McCall via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 7 07:31:21 PDT 2020
Author: Sam McCall
Date: 2020-10-07T16:31:09+02:00
New Revision: 4cae6228d129d4c4dfb156c043977bb6b5690031
URL: https://github.com/llvm/llvm-project/commit/4cae6228d129d4c4dfb156c043977bb6b5690031
DIFF: https://github.com/llvm/llvm-project/commit/4cae6228d129d4c4dfb156c043977bb6b5690031.diff
LOG: [ADT] function_ref's constructor is unavailable if the argument is not callable.
This allows overload sets containing function_ref arguments to work correctly
Otherwise they're ambiguous as anything "could be" converted to a function_ref.
This matches proposed std::function_ref, absl::function_ref, etc.
Differential Revision: https://reviews.llvm.org/D88901
Added:
Modified:
llvm/include/llvm/ADT/STLExtras.h
llvm/lib/AsmParser/LLParser.h
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
llvm/unittests/ADT/FunctionRefTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index 4be016b795a0..b70a6f9fc381 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -186,16 +186,27 @@ class function_ref<Ret(Params...)> {
std::forward<Params>(params)...);
}
+ template <typename Callable,
+ typename Result =
+ typename std::result_of<Callable(Params...)>::type>
+ static constexpr bool IsCompatible =
+ std::is_void<Ret>::value || std::is_convertible<Result, Ret>::value;
+
public:
function_ref() = default;
function_ref(std::nullptr_t) {}
template <typename Callable>
+ // Only allow this constructor if the object is actually callable
+ // and returns the correct type.
function_ref(
Callable &&callable,
std::enable_if_t<
+ // This is not the copy-constructor.
!std::is_same<std::remove_cv_t<std::remove_reference_t<Callable>>,
- function_ref>::value> * = nullptr)
+ function_ref>::value &&
+ // Must be callable and return a suitable type.
+ IsCompatible<Callable>> * = nullptr)
: callback(callback_fn<typename std::remove_reference<Callable>::type>),
callable(reinterpret_cast<intptr_t>(&callable)) {}
diff --git a/llvm/lib/AsmParser/LLParser.h b/llvm/lib/AsmParser/LLParser.h
index a7fbcdd5abc5..5f581f0d4efb 100644
--- a/llvm/lib/AsmParser/LLParser.h
+++ b/llvm/lib/AsmParser/LLParser.h
@@ -166,8 +166,8 @@ namespace llvm {
: Context(Context), Lex(F, SM, Err, Context), M(M), Index(Index),
Slots(Slots), BlockAddressPFS(nullptr) {}
bool Run(
- bool UpgradeDebugInfo,
- DataLayoutCallbackTy DataLayoutCallback = [](Module *) {});
+ bool UpgradeDebugInfo, DataLayoutCallbackTy DataLayoutCallback =
+ [](StringRef) { return None; });
bool parseStandaloneConstantValue(Constant *&C, const SlotMapping *Slots);
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 4d69dd7dcc5d..15ca3a54da2d 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -579,9 +579,7 @@ class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
/// \returns true if an error occurred.
Error parseBitcodeInto(
Module *M, bool ShouldLazyLoadMetadata = false, bool IsImporting = false,
- DataLayoutCallbackTy DataLayoutCallback = [](std::string) {
- return None;
- });
+ DataLayoutCallbackTy DataLayoutCallback = [](StringRef) { return None; });
static uint64_t decodeSignRotatedValue(uint64_t V);
diff --git a/llvm/unittests/ADT/FunctionRefTest.cpp b/llvm/unittests/ADT/FunctionRefTest.cpp
index 669b87dbf8e4..f084aa7a660b 100644
--- a/llvm/unittests/ADT/FunctionRefTest.cpp
+++ b/llvm/unittests/ADT/FunctionRefTest.cpp
@@ -48,4 +48,15 @@ TEST(FunctionRefTest, BadCopy) {
ASSERT_EQ(1, X());
}
+// Test that overloads on function_refs are resolved as expected.
+const char *returns(StringRef) { return "not a function"; }
+const char *returns(function_ref<double()> F) { return "number"; }
+const char *returns(function_ref<StringRef()> F) { return "string"; }
+
+TEST(FunctionRefTest, SFINAE) {
+ EXPECT_EQ("not a function", returns("boo!"));
+ EXPECT_EQ("number", returns([] { return 42; }));
+ EXPECT_EQ("string", returns([] { return "hello"; }));
+}
+
} // namespace
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