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>
14 lines
902 B
C++
14 lines
902 B
C++
// RUN: %clang_cc1 -std=c++20 -Wc++17-compat -verify -Wno-unused %s
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class X {};
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template<typename T>
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class B3 { // expected-note {{candidate template ignored: could not match 'B3<T>' against 'int'}} \
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// expected-note {{implicit deduction guide declared as 'template <typename T> B3(B3<T>) -> B3<T>'}}
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template<X x> B3(T); // expected-warning 2{{non-type template parameter of type 'X' is incompatible with C++ standards before C++20}} \
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// expected-note {{candidate template ignored: couldn't infer template argument 'x'}} \
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// expected-note {{implicit deduction guide declared as 'template <typename T, X x> B3(T) -> B3<T>'}}
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};
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B3 b3 = 0; // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'B3'}} \
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// expected-note {{while building implicit deduction guide first needed here}}
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