3b639d7d1d
Given the following invalid code,
```cpp
template <class T>
struct S {
T *a;
};
S s = {1};
```
we produce such diagnostics currently:
```
<source>:2:8: note: candidate template ignored: could not match 'S<T>' against 'int'
2 | struct S {
| ^
<source>:2:8: note: candidate template ignored: could not match 'T *' against 'int'
```
Which I think is confusing because there's no `S<T>` nor `T *` at the
location it points to. This is because we're deducing the initializer
against implicitly generated deduction guides, and their source
locations just point to the corresponding `RecordDecl`. Hence the
misleading notes.
This patch alleviates the issue by adding extra notes demonstrating
which implicit deduction guide we're deducing against. In other words,
in addition to the note of `could not match 'T *' against 'int'`, we
would also say the implicit deduction guide we're trying to use:
`template <class T> S(T *) -> S<T>`, which looks clearer IMO.
---------
Co-authored-by: Sirraide <aeternalmail@gmail.com>
104 lines
3.0 KiB
C++
104 lines
3.0 KiB
C++
// RUN: %clang_cc1 -std=c++20 -verify %s
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template<class T> struct S {
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template<class U> struct N {
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N(T) {}
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N(T, U) {}
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template<class V> N(V, U) {}
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};
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};
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S<int>::N x{"a", 1};
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using T = decltype(x);
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using T = S<int>::N<int>;
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template<class X> struct default_ftd_argument {
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template<class Y> struct B {
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template<class W = X, class Z = Y, class V = Z, int I = 0> B(Y);
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};
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};
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default_ftd_argument<int>::B default_arg("a");
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using DefaultArg = decltype(default_arg);
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using DefaultArg = default_ftd_argument<int>::B<const char *>;
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template<bool> struct test;
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template<class X> struct non_type_param {
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template<class Y> struct B {
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B(Y);
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template<class Z, test<Z::value> = 0> B(Z);
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};
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};
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non_type_param<int>::B ntp = 5;
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using NonTypeParam = decltype(ntp);
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using NonTypeParam = non_type_param<int>::B<int>;
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template<typename A, typename T>
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concept True = true;
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template<typename T>
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concept False = false;
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template<class X> struct concepts {
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template<class Y> struct B {
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template<class K = X, True<K> Z> B(Y, Z);
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};
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};
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concepts<int>::B cc(1, 3);
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using Concepts = decltype(cc);
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using Concepts = concepts<int>::B<int>;
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template<class X> struct requires_clause {
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template<class Y> struct B {
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template<class Z> requires true
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B(Y, Z);
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};
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};
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requires_clause<int>::B req(1, 2);
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using RC = decltype(req);
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using RC = requires_clause<int>::B<int>;
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template<typename X> struct nested_init_list {
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template<True<X> Y>
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struct B {
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X x;
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Y y;
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};
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template<False F>
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struct concept_fail { // #INIT_LIST_INNER_INVALID
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X x;
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F f;
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};
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};
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nested_init_list<int>::B nil {1, 2};
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using NIL = decltype(nil);
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using NIL = nested_init_list<int>::B<int>;
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// expected-error@+1 {{no viable constructor or deduction guide for deduction of template arguments of 'nested_init_list<int>::concept_fail'}}
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nested_init_list<int>::concept_fail nil_invalid{1, ""};
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// expected-note@#INIT_LIST_INNER_INVALID {{candidate template ignored: substitution failure [with F = const char *]: constraints not satisfied for class template 'concept_fail' [with F = const char *]}}
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// expected-note@#INIT_LIST_INNER_INVALID {{implicit deduction guide declared as 'template <False F> concept_fail(int, F) -> concept_fail<F>'}}
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// expected-note@#INIT_LIST_INNER_INVALID {{candidate function template not viable: requires 1 argument, but 2 were provided}}
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// expected-note@#INIT_LIST_INNER_INVALID {{implicit deduction guide declared as 'template <False F> concept_fail(concept_fail<F>) -> concept_fail<F>'}}
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// expected-note@#INIT_LIST_INNER_INVALID {{candidate function template not viable: requires 0 arguments, but 2 were provided}}
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// expected-note@#INIT_LIST_INNER_INVALID {{implicit deduction guide declared as 'template <False F> concept_fail() -> concept_fail<F>'}}
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namespace GH88142 {
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template <typename, typename...> struct X {
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template <typename> struct Y {
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template <typename T> Y(T) {}
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};
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template <typename T> Y(T) -> Y<T>;
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};
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X<int>::Y y(42);
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} // namespace PR88142
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