fd5277c063
Specifically, the following features are not included in this commit:
- any sort of capturing within generic lambdas
- nested lambdas
- conversion operator for captureless lambdas
- ensuring all visitors are generic lambda aware
As an example of what compiles:
template <class F1, class F2>
struct overload : F1, F2 {
using F1::operator();
using F2::operator();
overload(F1 f1, F2 f2) : F1(f1), F2(f2) { }
};
auto Recursive = [](auto Self, auto h, auto ... rest) {
return 1 + Self(Self, rest...);
};
auto Base = [](auto Self, auto h) {
return 1;
};
overload<decltype(Base), decltype(Recursive)> O(Base, Recursive);
int num_params = O(O, 5, 3, "abc", 3.14, 'a');
Please see attached tests for more examples.
Some implementation notes:
- Add a new Declarator context => LambdaExprParameterContext to
clang::Declarator to allow the use of 'auto' in declaring generic
lambda parameters
- Augment AutoType's constructor (similar to how variadic
template-type-parameters ala TemplateTypeParmDecl are implemented) to
accept an IsParameterPack to encode a generic lambda parameter pack.
- Add various helpers to CXXRecordDecl to facilitate identifying
and querying a closure class
- LambdaScopeInfo (which maintains the current lambda's Sema state)
was augmented to house the current depth of the template being
parsed (id est the Parser calls Sema::RecordParsingTemplateParameterDepth)
so that Sema::ActOnLambdaAutoParameter may use it to create the
appropriate list of corresponding TemplateTypeParmDecl for each
auto parameter identified within the generic lambda (also stored
within the current LambdaScopeInfo). Additionally,
a TemplateParameterList data-member was added to hold the invented
TemplateParameterList AST node which will be much more useful
once we teach TreeTransform how to transform generic lambdas.
- SemaLambda.h was added to hold some common lambda utility
functions (this file is likely to grow ...)
- Teach Sema::ActOnStartOfFunctionDef to check whether it
is being called to instantiate a generic lambda's call
operator, and if so, push an appropriately prepared
LambdaScopeInfo object on the stack.
- Teach Sema::ActOnStartOfLambdaDefinition to set the
return type of a lambda without a trailing return type
to 'auto' in C++1y mode, and teach the return type
deduction machinery in SemaStmt.cpp to process either
C++11 and C++14 lambda's correctly depending on the flag.
- various tests were added - but much more will be needed.
A greatful thanks to all reviewers including Eli Friedman,
James Dennett and the ever illuminating Richard Smith. And
yet I am certain that I have allowed unidentified bugs to creep in;
bugs, that I will do my best to slay, once identified!
Thanks!
llvm-svn: 188977
66 lines
1.9 KiB
C++
66 lines
1.9 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -std=c++1y %s -verify
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int a;
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int &b = [] (int &r) -> decltype(auto) { return r; } (a);
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int &c = [] (int &r) -> decltype(auto) { return (r); } (a);
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int &d = [] (int &r) -> auto & { return r; } (a);
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int &e = [] (int &r) -> auto { return r; } (a); // expected-error {{cannot bind to a temporary}}
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int &f = [] (int r) -> decltype(auto) { return r; } (a); // expected-error {{cannot bind to a temporary}}
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int &g = [] (int r) -> decltype(auto) { return (r); } (a); // expected-warning {{reference to stack}}
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int test_explicit_auto_return()
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{
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struct X {};
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auto L = [](auto F, auto a) { return F(a); };
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auto M = [](auto a) -> auto { return a; }; // OK
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auto MRef = [](auto b) -> auto& { return b; }; //expected-warning{{reference to stack}}
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auto MPtr = [](auto c) -> auto* { return &c; }; //expected-warning{{address of stack}}
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auto MDeclType = [](auto&& d) -> decltype(auto) { return static_cast<decltype(d)>(d); }; //OK
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M(3);
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auto &&x = MDeclType(X{});
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auto &&x1 = M(X{});
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auto &&x2 = MRef(X{});//expected-note{{in instantiation of}}
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auto &&x3 = MPtr(X{}); //expected-note{{in instantiation of}}
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return 0;
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}
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int test_implicit_auto_return()
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{
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{
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auto M = [](auto a) { return a; };
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struct X {};
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X x = M(X{});
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}
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}
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int test_multiple_returns() {
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auto M = [](auto a) {
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bool k;
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if (k)
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return a;
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else
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return 5; //expected-error{{deduced as 'int' here}}
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};
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M(3); // OK
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M('a'); //expected-note{{in instantiation of}}
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return 0;
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}
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int test_no_parameter_list()
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{
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static int si = 0;
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auto M = [] { return 5; }; // OK
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auto M2 = [] -> auto&& { return si; }; // expected-error{{lambda requires '()'}}
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M();
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}
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int test_conditional_in_return() {
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auto Fac = [](auto f, auto n) {
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return n <= 0 ? n : f(f, n - 1) * n;
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};
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// FIXME: this test causes a recursive limit - need to error more gracefully.
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//Fac(Fac, 3);
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} |