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Summary: C++1z 6.4.1/p2: If the if statement is of the form if constexpr, the value of the condition shall be a contextually converted constant expression of type bool [...] C++1z 5.20/p4: [...] A contextually converted constant expression of type bool is an expression, contextually converted to bool (Clause4), where the converted expression is a constant expression and the conversion sequence contains only the conversions above. [...] Contextually converting result of an expression `e` to a Boolean value requires `bool t(e)` to be well-formed. An explicit conversion function is only considered as a user-defined conversion for direct-initialization, which is essentially what //contextually converted to bool// requires. Also, fixes PR28470. Reviewers: rsmith Subscribers: cfe-commits Differential Revision: https://reviews.llvm.org/D24158 llvm-svn: 280838
35 lines
666 B
C++
35 lines
666 B
C++
// RUN: %clang_cc1 -std=c++1z %s -emit-llvm -o - | FileCheck %s --implicit-check-not=should_not_be_used
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void should_be_used_1();
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void should_be_used_2();
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void should_be_used_3();
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void should_not_be_used();
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struct A {
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constexpr explicit operator bool() const {
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return true;
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}
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};
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void f() {
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if constexpr (false)
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should_not_be_used();
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else
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should_be_used_1();
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if constexpr (true || ({ label: false; }))
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should_be_used_2();
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else {
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goto foo;
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foo: should_not_be_used();
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}
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if constexpr (A())
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should_be_used_3();
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else
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should_not_be_used();
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}
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// CHECK: should_be_used_1
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// CHECK: should_be_used_2
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// CHECK: should_be_used_3
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