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>
28 lines
1.4 KiB
C++
28 lines
1.4 KiB
C++
// RUN: %clang_cc1 -fsyntax-only -verify=expected,precxx17 %std_cxx98-14 %s
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// RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx17 %std_cxx17- %s
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template<typename T,
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int I,
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template<typename> class TT>
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class A; // precxx17-note 3 {{template is declared here}} \
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cxx17-note 2 {{template is declared here}} \
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cxx17-note {{candidate template ignored: couldn't infer template argument 'T'}} \
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cxx17-note {{implicit deduction guide declared as 'template <typename T, int I, template <typename> class TT> A(A<T, I, TT>) -> A<T, I, TT>'}} \
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cxx17-note {{candidate function template not viable: requires 1 argument, but 0 were provided}} \
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cxx17-note {{implicit deduction guide declared as 'template <typename T, int I, template <typename> class TT> A() -> A<T, I, TT>'}} \
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template<typename> class X;
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A<int, 0, X> * a1;
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A<float, 1, X, double> *a2; // expected-error{{too many template arguments for class template 'A'}}
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A<float, 1> *a3; // expected-error{{too few template arguments for class template 'A'}}
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A a4; // precxx17-error{{use of class template 'A' requires template arguments}} \
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cxx17-error{{no viable constructor or deduction guide for deduction of template arguments of 'A'}}
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namespace test0 {
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template <class t> class foo {};
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template <class t> class bar {
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bar(::test0::foo<tee> *ptr) {} // expected-error {{use of undeclared identifier 'tee'}}
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};
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}
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