[clang] da928c6 - [Clang][Sema] ASTContext::getUnconstrainedType propagates dependence (#92425)
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Thu May 16 11:10:51 PDT 2024
Author: Krystian Stasiowski
Date: 2024-05-16T14:10:46-04:00
New Revision: da928c6d6e0e2f619fdaef71cea8747d9aef188d
URL: https://github.com/llvm/llvm-project/commit/da928c6d6e0e2f619fdaef71cea8747d9aef188d
DIFF: https://github.com/llvm/llvm-project/commit/da928c6d6e0e2f619fdaef71cea8747d9aef188d.diff
LOG: [Clang][Sema] ASTContext::getUnconstrainedType propagates dependence (#92425)
When the argument passed to `ASTContext::getUnconstrainedType` is an
unconstrained `AutoType`, will return the argument unchanged. However,
when called with a constrained `AutoType`, an unconstrained,
non-dependent `AutoType` will be returned even if the argument was
dependent. Consider the following:
```
template<typename T>
concept C = sizeof(T) == sizeof(int);
template<auto N>
struct A;
template<C auto N>
struct A<N>; // error: class template partial specialization is not more specialized than the primary template
```
When comparing the template parameters for equivalence,
`ASTContext::getUnconstrainedType` is used to remove the constraints per
[temp.over.link] p6 sentence 2. For the template
parameter `N` of the class template, it returns a dependent `AutoType`.
For the template parameter `N` of the class template partial
specialization, it returns a non-dependent `AutoType`. We subsequently
compare the adjusted types and find they are not equivalent, thus we
consider the partial specialization to not be more specialized than the
primary template per [temp.func.order] p6.2.2.
This patch changes `ASTContext::getUnconstrainedType` such that the
dependence of a constrained `AutoType` will propagate to the returned
unconstrained `AutoType`. This causes the above example to be correctly
accepted, fixing #77377.
Added:
clang/test/CXX/temp/temp.decls/temp.fct/temp.func.order/p2.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/lib/AST/ASTContext.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index be4cded276321..2d2928e418623 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -723,6 +723,7 @@ Bug Fixes to C++ Support
- Clang now ignores template parameters only used within the exception specification of candidate function
templates during partial ordering when deducing template arguments from a function declaration or when
taking the address of a function template.
+- Fix a bug with checking constrained non-type template parameters for equivalence. Fixes (#GH77377).
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 4475f399a120b..8fc2bb8c401c2 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5910,7 +5910,8 @@ QualType ASTContext::getUnconstrainedType(QualType T) const {
if (auto *AT = CanonT->getAs<AutoType>()) {
if (!AT->isConstrained())
return T;
- return getQualifiedType(getAutoType(QualType(), AT->getKeyword(), false,
+ return getQualifiedType(getAutoType(QualType(), AT->getKeyword(),
+ AT->isDependentType(),
AT->containsUnexpandedParameterPack()),
T.getQualifiers());
}
diff --git a/clang/test/CXX/temp/temp.decls/temp.fct/temp.func.order/p2.cpp b/clang/test/CXX/temp/temp.decls/temp.fct/temp.func.order/p2.cpp
new file mode 100644
index 0000000000000..df1bbd5fe8128
--- /dev/null
+++ b/clang/test/CXX/temp/temp.decls/temp.fct/temp.func.order/p2.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// expected-no-diagnostics
+
+namespace GH77377 {
+ template<typename T>
+ concept C = sizeof(T) == sizeof(int);
+
+ template<auto N>
+ struct A;
+
+ template<C auto N>
+ struct A<N>;
+}
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