a734ab9808
Support the constexpr specifier on lambda expressions - and support its inference from the lambda call operator's body.
i.e.
auto L = [] () constexpr { return 5; };
static_assert(L() == 5); // OK
auto Implicit = [] (auto a) { return a; };
static_assert(Implicit(5) == 5);
We do not support evaluation of lambda's within constant expressions just yet.
Implementation Strategy:
- teach ParseLambdaExpressionAfterIntroducer to expect a constexpr specifier and mark the invented function call operator's declarator's decl-specifier with it; Have it emit fixits for multiple decl-specifiers (mutable or constexpr) in this location.
- for cases where constexpr is not explicitly specified, have buildLambdaExpr check whether the invented function call operator satisfies the requirements of a constexpr function, by calling CheckConstexprFunctionDecl/Body.
Much obliged to Richard Smith for his patience and his care, in ensuring the code is clang-worthy.
llvm-svn: 264513
36 lines
1.2 KiB
C++
36 lines
1.2 KiB
C++
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s
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// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s
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// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fms-extensions %s
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// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing -fms-extensions %s
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namespace test_constexpr_checking {
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namespace ns1 {
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struct NonLit { ~NonLit(); }; //expected-note{{not literal}}
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auto L = [](NonLit NL) constexpr { }; //expected-error{{not a literal type}}
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} // end ns1
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namespace ns2 {
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auto L = [](int I) constexpr { asm("non-constexpr"); }; //expected-error{{not allowed in constexpr function}}
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} // end ns1
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} // end ns test_constexpr_checking
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namespace test_constexpr_call {
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namespace ns1 {
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auto L = [](int I) { return I; };
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static_assert(L(3) == 3);
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} // end ns1
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namespace ns2 {
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auto L = [](auto a) { return a; };
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static_assert(L(3) == 3);
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static_assert(L(3.14) == 3.14);
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}
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namespace ns3 {
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auto L = [](auto a) { asm("non-constexpr"); return a; }; //expected-note{{declared here}}
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constexpr int I = //expected-error{{must be initialized by a constant expression}}
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L(3); //expected-note{{non-constexpr function}}
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}
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} // end ns test_constexpr_call
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