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
931 B
C++
14 lines
931 B
C++
// RUN: rm -rf %t
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// RUN: mkdir -p %t
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// RUN: %clang_cc1 -std=c++20 %S/Inputs/template_name_lookup/foo.cppm -emit-module-interface -o %t/foo.pcm
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// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %s -fsyntax-only -verify
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import foo;
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void use() {
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X x; // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'X'}}
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// expected-note@Inputs/template_name_lookup/foo.cppm:3 {{candidate template ignored: couldn't infer template argument 'T'}}
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// expected-note@Inputs/template_name_lookup/foo.cppm:3 {{implicit deduction guide declared as 'template <typename T> X(X<T>) -> X<T>'}}
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// expected-note@Inputs/template_name_lookup/foo.cppm:3 {{candidate function template not viable: requires 1 argument, but 0 were provided}}
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// expected-note@Inputs/template_name_lookup/foo.cppm:3 {{implicit deduction guide declared as 'template <typename T> X() -> X<T>'}}
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}
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