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Per P1975R0 an expression like `static_cast<U[]>(...)` defines the type
of the expression as U[1].
Fixes https://github.com/llvm/llvm-project/issues/62863
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D152003
Files:
clang/docs/ReleaseNotes.rst
clang/lib/Sema/SemaType.cpp
clang/test/SemaCXX/paren-list-agg-init.cpp
Index: clang/test/SemaCXX/paren-list-agg-init.cpp
===================================================================
--- clang/test/SemaCXX/paren-list-agg-init.cpp
+++ clang/test/SemaCXX/paren-list-agg-init.cpp
@@ -272,3 +272,14 @@
// expected-warning@-1 {{braces around scalar init}}
// beforecxx20-warning@-2 {{aggregate initialization of type 'A' from a
parenthesized list of values is a C++20 extension}}
}
+
+namespace gh62863 {
+int (&&arr)[] = static_cast<int[]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a
parenthesized list of values is a C++20 extension}}
+int (&&arr1)[1] = static_cast<int[]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a
parenthesized list of values is a C++20 extension}}
+int (&&arrr2)[2] = static_cast<int[]>(42); // expected-error {{reference to
type 'int[2]' could not bind to an rvalue of type 'int[1]'}}
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a
parenthesized list of values is a C++20 extension}}
+int (&&arr3)[3] = static_cast<int[3]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[3]' from a
parenthesized list of values is a C++20 extension}}
+}
Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -8818,6 +8818,17 @@
}
}
}
+ // C++20 [expr.static.cast]p.4: ... If T is “array of unknown bound of U”,
+ // this direct-initialization defines the type of the expression as U[1]
+ if (auto *Cast = dyn_cast<CXXStaticCastExpr>(E)) {
+ if (auto *SubInit = dyn_cast<CXXParenListInitExpr>(Cast->getSubExpr())) {
+ const Type *InnerType = SubInit->getType().getTypePtr();
+ if (const auto *AT = dyn_cast<ConstantArrayType>(InnerType);
+ AT && AT->getSize() == 1) {
+ Cast->setType(SubInit->getType());
+ }
+ }
+ }
}
QualType Sema::getCompletedType(Expr *E) {
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -463,6 +463,8 @@
- Fix crash when passing a braced initializer list to a parentehsized aggregate
initialization expression.
(`#63008 <https://github.com/llvm/llvm-project/issues/63008>`_).
+- Fixed `static_cast` to array of unknown bound.
+ (`#62863 <https://github.com/llvm/llvm-project/issues/62863>`_).
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Index: clang/test/SemaCXX/paren-list-agg-init.cpp
===================================================================
--- clang/test/SemaCXX/paren-list-agg-init.cpp
+++ clang/test/SemaCXX/paren-list-agg-init.cpp
@@ -272,3 +272,14 @@
// expected-warning@-1 {{braces around scalar init}}
// beforecxx20-warning@-2 {{aggregate initialization of type 'A' from a parenthesized list of values is a C++20 extension}}
}
+
+namespace gh62863 {
+int (&&arr)[] = static_cast<int[]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a parenthesized list of values is a C++20 extension}}
+int (&&arr1)[1] = static_cast<int[]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a parenthesized list of values is a C++20 extension}}
+int (&&arrr2)[2] = static_cast<int[]>(42); // expected-error {{reference to type 'int[2]' could not bind to an rvalue of type 'int[1]'}}
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[1]' from a parenthesized list of values is a C++20 extension}}
+int (&&arr3)[3] = static_cast<int[3]>(42);
+// beforecxx20-warning@-1 {{aggregate initialization of type 'int[3]' from a parenthesized list of values is a C++20 extension}}
+}
Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -8818,6 +8818,17 @@
}
}
}
+ // C++20 [expr.static.cast]p.4: ... If T is âarray of unknown bound of Uâ,
+ // this direct-initialization defines the type of the expression as U[1]
+ if (auto *Cast = dyn_cast<CXXStaticCastExpr>(E)) {
+ if (auto *SubInit = dyn_cast<CXXParenListInitExpr>(Cast->getSubExpr())) {
+ const Type *InnerType = SubInit->getType().getTypePtr();
+ if (const auto *AT = dyn_cast<ConstantArrayType>(InnerType);
+ AT && AT->getSize() == 1) {
+ Cast->setType(SubInit->getType());
+ }
+ }
+ }
}
QualType Sema::getCompletedType(Expr *E) {
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -463,6 +463,8 @@
- Fix crash when passing a braced initializer list to a parentehsized aggregate
initialization expression.
(`#63008 <https://github.com/llvm/llvm-project/issues/63008>`_).
+- Fixed `static_cast` to array of unknown bound.
+ (`#62863 <https://github.com/llvm/llvm-project/issues/62863>`_).
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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