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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Return type deduction for auto fails for member function in struct nested in lambda nested in function template"
href="https://bugs.llvm.org/show_bug.cgi?id=32766">32766</a>
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<th>Summary</th>
<td>Return type deduction for auto fails for member function in struct nested in lambda nested in function template
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>4.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++14
</td>
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<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>arnetheduck@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Here's a snippet which I *think* should compile (it does so with gcc/icc), but
fails under clang 4.0 - <a href="https://godbolt.org/g/8oCnrm">https://godbolt.org/g/8oCnrm</a>
It works if any of the following are true:
* f is not a template function
* xxx is not a auto parameter
* v does not return auto
* R is not nested in y
template <typename F>
void f() {
auto y = [=] (auto xxx) {
struct R {
static constexpr auto v() { return 42; }
};
};
y(32);
}
void x() {
f<int>();
}
<source>:5:49: error: cannot initialize return object of type 'auto' with an
rvalue of type 'int'
static constexpr auto v() { return 42; }
^~
<source>:4:17: note: in instantiation of member function 'f()::(anonymous
class)::operator()(type-parameter-0-0)::R::v' requested here
struct R {
^
<source>:13:5: note: in instantiation of function template specialization
'f<int>' requested here
f<int>();
^
1 error generated.
Compiler exited with result code 1
The example looks a little convoluted but comes from real life in some
callback-heavy async code, deep down in a library.</pre>
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