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llvm-6502/unittests/Support/ErrorOrTest.cpp
David Blaikie 38a4f3bbec Ensure ErrorOr cannot implicitly invoke explicit ctors of the underlying type.
An unpleasant surprise while migrating unique_ptrs (see changes in
lib/Object): ErrorOr<int*> was implicitly convertible to
ErrorOr<std::unique_ptr<int>>.

Keep the explicit conversions otherwise it's a pain to convert
ErrorOr<int*> to ErrorOr<std::unique_ptr<int>>.

I'm not sure if there should be more SFINAE on those explicit ctors (I
could check if !is_convertible && is_constructible, but since the ctor
has to be called explicitly I don't think there's any need to disable
them when !is_constructible - they'll just fail anyway. It's the
converting ctors that can create interesting ambiguities without proper
SFINAE). I had to SFINAE the explicit ones because otherwise they'd be
ambiguous with the implicit ones in an explicit context, so far as I
could tell.

The converting assignment operators seemed unnecessary (and similarly
buggy/dangerous) - just rely on the converting ctors to convert to the
right type for assignment instead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217048 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-03 17:31:25 +00:00

96 lines
2.8 KiB
C++

//===- unittests/ErrorOrTest.cpp - ErrorOr.h tests ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/Errc.h"
#include "gtest/gtest.h"
#include <memory>
using namespace llvm;
namespace {
ErrorOr<int> t1() {return 1;}
ErrorOr<int> t2() { return errc::invalid_argument; }
TEST(ErrorOr, SimpleValue) {
ErrorOr<int> a = t1();
// FIXME: This is probably a bug in gtest. EXPECT_TRUE should expand to
// include the !! to make it friendly to explicit bool operators.
EXPECT_TRUE(!!a);
EXPECT_EQ(1, *a);
ErrorOr<int> b = a;
EXPECT_EQ(1, *b);
a = t2();
EXPECT_FALSE(a);
EXPECT_EQ(a.getError(), errc::invalid_argument);
#ifdef EXPECT_DEBUG_DEATH
EXPECT_DEBUG_DEATH(*a, "Cannot get value when an error exists");
#endif
}
ErrorOr<std::unique_ptr<int> > t3() {
return std::unique_ptr<int>(new int(3));
}
TEST(ErrorOr, Types) {
int x;
ErrorOr<int&> a(x);
*a = 42;
EXPECT_EQ(42, x);
// Move only types.
EXPECT_EQ(3, **t3());
}
struct B {};
struct D : B {};
TEST(ErrorOr, Covariant) {
ErrorOr<B*> b(ErrorOr<D*>(nullptr));
b = ErrorOr<D*>(nullptr);
ErrorOr<std::unique_ptr<B> > b1(ErrorOr<std::unique_ptr<D> >(nullptr));
b1 = ErrorOr<std::unique_ptr<D> >(nullptr);
ErrorOr<std::unique_ptr<int>> b2(ErrorOr<int *>(nullptr));
ErrorOr<int *> b3(nullptr);
ErrorOr<std::unique_ptr<int>> b4(b3);
}
// ErrorOr<int*> x(nullptr);
// ErrorOr<std::unique_ptr<int>> y = x; // invalid conversion
static_assert(
!std::is_convertible<const ErrorOr<int *> &,
ErrorOr<std::unique_ptr<int>>>::value,
"do not invoke explicit ctors in implicit conversion from lvalue");
// ErrorOr<std::unique_ptr<int>> y = ErrorOr<int*>(nullptr); // invalid
// // conversion
static_assert(
!std::is_convertible<ErrorOr<int *> &&,
ErrorOr<std::unique_ptr<int>>>::value,
"do not invoke explicit ctors in implicit conversion from rvalue");
// ErrorOr<int*> x(nullptr);
// ErrorOr<std::unique_ptr<int>> y;
// y = x; // invalid conversion
static_assert(!std::is_assignable<ErrorOr<std::unique_ptr<int>>,
const ErrorOr<int *> &>::value,
"do not invoke explicit ctors in assignment");
// ErrorOr<std::unique_ptr<int>> x;
// x = ErrorOr<int*>(nullptr); // invalid conversion
static_assert(!std::is_assignable<ErrorOr<std::unique_ptr<int>>,
ErrorOr<int *> &&>::value,
"do not invoke explicit ctors in assignment");
} // end anon namespace