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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - diagnose assignment at top level in constant-expression better" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D24250&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=zyLzl1SqRei8nG93LQOMIgIa_m17E6D4SdwCCee_6O4&s=yNyyN5JtF2ux_q83wbCPGfQvTbyPw4Vocm08B2_sMTo&e=">24250</a>
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<th>Summary</th>
<td>diagnose assignment at top level in constant-expression better
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>richard-llvm@metafoo.co.uk
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<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Top-level assignment in a constant-expression is forbidden by the grammar (and
thus rejected in Clang's parser). This results in some confusing diagnostics:
struct N { constexpr int operator=(int n) { return n; } } n;
int a[n = 0];
template<int> struct X {};
X<n = 0> x;
enum E { e = n = 0 };
struct Q { int k : n = 0; };
Gives:
<stdin>:2:9: error: expected ']'
int a[n = 0];
^
<stdin>:2:6: note: to match this '['
int a[n = 0];
^
<stdin>:2:7: error: size of array has non-integer type 'struct N'
int a[n = 0];
^
<stdin>:4:5: error: expected '>'
X<n = 0> x;
^
<stdin>:4:5: error: expected unqualified-id
<stdin>:5:14: error: integral constant expression must have integral or
unscoped enumeration type, not 'struct N'
enum E { e = n = 0 };
^
<stdin>:5:16: error: expected '}' or ','
enum E { e = n = 0 };
^
<stdin>:6:22: error: bitfield member cannot have an in-class initializer
struct Q { int k : n = 0; };
^
<stdin>:6:20: error: integral constant expression must have integral or
unscoped enumeration type, not 'struct N'
struct Q { int k : n = 0; };
^
It would be nice to diagnose these cases better (except for the last case,
where the current diagnostic seems appropriate).</pre>
</div>
</p>
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