r348239 - [WIP][Sema] Improve static_assert diagnostics for type traits.
Clement Courbet via cfe-commits
cfe-commits at lists.llvm.org
Mon Dec 3 23:59:57 PST 2018
Author: courbet
Date: Mon Dec 3 23:59:57 2018
New Revision: 348239
URL: http://llvm.org/viewvc/llvm-project?rev=348239&view=rev
Log:
[WIP][Sema] Improve static_assert diagnostics for type traits.
Summary:
In our codebase, `static_assert(std::some_type_trait<Ts...>::value, "msg")`
(where `some_type_trait` is an std type_trait and `Ts...` is the
appropriate template parameters) account for 11.2% of the `static_assert`s.
In these cases, the `Ts` are typically not spelled out explicitly, e.g.
`static_assert(std::is_same<SomeT::TypeT, typename SomeDependentT::value_type>::value, "message");`
The diagnostic when the assert fails is typically not very useful, e.g.
`static_assert failed due to requirement 'std::is_same<SomeT::TypeT, typename SomeDependentT::value_type>::value' "message"`
This change makes the diagnostic spell out the types explicitly , e.g.
`static_assert failed due to requirement 'std::is_same<int, float>::value' "message"`
See tests for more examples.
After this is submitted, I intend to handle
`static_assert(!std::some_type_trait<Ts...>::value, "msg")`,
which is another 6.6% of static_asserts.
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D54903
Added:
cfe/trunk/test/SemaCXX/static-assert-cxx17.cpp
Modified:
cfe/trunk/include/clang/AST/NestedNameSpecifier.h
cfe/trunk/lib/AST/NestedNameSpecifier.cpp
cfe/trunk/lib/Sema/SemaTemplate.cpp
cfe/trunk/test/SemaCXX/static-assert.cpp
Modified: cfe/trunk/include/clang/AST/NestedNameSpecifier.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/NestedNameSpecifier.h?rev=348239&r1=348238&r2=348239&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/NestedNameSpecifier.h (original)
+++ cfe/trunk/include/clang/AST/NestedNameSpecifier.h Mon Dec 3 23:59:57 2018
@@ -212,9 +212,12 @@ public:
/// parameter pack (for C++11 variadic templates).
bool containsUnexpandedParameterPack() const;
- /// Print this nested name specifier to the given output
- /// stream.
- void print(raw_ostream &OS, const PrintingPolicy &Policy) const;
+ /// Print this nested name specifier to the given output stream. If
+ /// `ResolveTemplateArguments` is true, we'll print actual types, e.g.
+ /// `ns::SomeTemplate<int, MyClass>` instead of
+ /// `ns::SomeTemplate<Container::value_type, T>`.
+ void print(raw_ostream &OS, const PrintingPolicy &Policy,
+ bool ResolveTemplateArguments = false) const;
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddPointer(Prefix.getOpaqueValue());
Modified: cfe/trunk/lib/AST/NestedNameSpecifier.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/NestedNameSpecifier.cpp?rev=348239&r1=348238&r2=348239&view=diff
==============================================================================
--- cfe/trunk/lib/AST/NestedNameSpecifier.cpp (original)
+++ cfe/trunk/lib/AST/NestedNameSpecifier.cpp Mon Dec 3 23:59:57 2018
@@ -16,6 +16,7 @@
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
#include "clang/AST/PrettyPrinter.h"
#include "clang/AST/TemplateName.h"
#include "clang/AST/Type.h"
@@ -270,9 +271,8 @@ bool NestedNameSpecifier::containsUnexpa
/// Print this nested name specifier to the given output
/// stream.
-void
-NestedNameSpecifier::print(raw_ostream &OS,
- const PrintingPolicy &Policy) const {
+void NestedNameSpecifier::print(raw_ostream &OS, const PrintingPolicy &Policy,
+ bool ResolveTemplateArguments) const {
if (getPrefix())
getPrefix()->print(OS, Policy);
@@ -305,6 +305,15 @@ NestedNameSpecifier::print(raw_ostream &
LLVM_FALLTHROUGH;
case TypeSpec: {
+ const auto *Record =
+ dyn_cast_or_null<ClassTemplateSpecializationDecl>(getAsRecordDecl());
+ if (ResolveTemplateArguments && Record) {
+ // Print the type trait with resolved template parameters.
+ Record->printName(OS);
+ printTemplateArgumentList(OS, Record->getTemplateArgs().asArray(),
+ Policy);
+ break;
+ }
const Type *T = getAsType();
PrintingPolicy InnerPolicy(Policy);
Modified: cfe/trunk/lib/Sema/SemaTemplate.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplate.cpp?rev=348239&r1=348238&r2=348239&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplate.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplate.cpp Mon Dec 3 23:59:57 2018
@@ -3052,6 +3052,28 @@ static Expr *lookThroughRangesV3Conditio
return Cond;
}
+// Print a diagnostic for the failing static_assert expression. Defaults to
+// pretty-printing the expression.
+static void prettyPrintFailedBooleanCondition(llvm::raw_string_ostream &OS,
+ const Expr *FailedCond,
+ const PrintingPolicy &Policy) {
+ const auto *DR = dyn_cast<DeclRefExpr>(FailedCond);
+ if (DR && DR->getQualifier()) {
+ // If this is a qualified name, expand the template arguments in nested
+ // qualifiers.
+ DR->getQualifier()->print(OS, Policy, true);
+ // Then print the decl itself.
+ const ValueDecl *VD = DR->getDecl();
+ OS << VD->getName();
+ if (const auto *IV = dyn_cast<VarTemplateSpecializationDecl>(VD)) {
+ // This is a template variable, print the expanded template arguments.
+ printTemplateArgumentList(OS, IV->getTemplateArgs().asArray(), Policy);
+ }
+ return;
+ }
+ FailedCond->printPretty(OS, nullptr, Policy);
+}
+
std::pair<Expr *, std::string>
Sema::findFailedBooleanCondition(Expr *Cond, bool AllowTopLevelCond) {
Cond = lookThroughRangesV3Condition(PP, Cond);
@@ -3093,7 +3115,7 @@ Sema::findFailedBooleanCondition(Expr *C
std::string Description;
{
llvm::raw_string_ostream Out(Description);
- FailedCond->printPretty(Out, nullptr, getPrintingPolicy());
+ prettyPrintFailedBooleanCondition(Out, FailedCond, getPrintingPolicy());
}
return { FailedCond, Description };
}
Added: cfe/trunk/test/SemaCXX/static-assert-cxx17.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/static-assert-cxx17.cpp?rev=348239&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/static-assert-cxx17.cpp (added)
+++ cfe/trunk/test/SemaCXX/static-assert-cxx17.cpp Mon Dec 3 23:59:57 2018
@@ -0,0 +1,47 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++1z -triple=x86_64-linux-gnu
+
+template <typename U, typename V>
+struct S1 {
+ static constexpr const bool value = false;
+};
+
+template <typename U, typename V>
+inline constexpr bool global_inline_var = S1<U, V>::value;
+
+template <typename T>
+struct S2 {
+ template <typename U, typename V>
+ static inline constexpr bool var = global_inline_var<U, V>;
+};
+
+template <typename U, typename V>
+void foo() {
+ static_assert(S1<U, V>::value);
+ // expected-error at -1{{static_assert failed due to requirement 'S1<int, float>::value'}}
+}
+template void foo<int, float>();
+// expected-note at -1{{in instantiation of function template specialization 'foo<int, float>' requested here}}
+
+template <typename U, typename V>
+void foo2() {
+ static_assert(global_inline_var<U, V>);
+ // expected-error at -1{{static_assert failed due to requirement 'global_inline_var<int, float>'}}
+}
+template void foo2<int, float>();
+// expected-note at -1{{in instantiation of function template specialization 'foo2<int, float>' requested here}}
+
+template <typename T, typename U, typename V>
+void foo3() {
+ static_assert(T::template var<U, V>);
+ // expected-error at -1{{static_assert failed due to requirement 'S2<long>::var<int, float>'}}
+}
+template void foo3<S2<long>, int, float>();
+// expected-note at -1{{in instantiation of function template specialization 'foo3<S2<long>, int, float>' requested here}}
+
+template <typename T>
+void foo4() {
+ static_assert(S1<T[sizeof(T)], int[4]>::value, "");
+ // expected-error at -1{{static_assert failed due to requirement 'S1<float [4], int [4]>::value'}}
+};
+template void foo4<float>();
+// expected-note at -1{{in instantiation of function template specialization 'foo4<float>' requested here}}
Modified: cfe/trunk/test/SemaCXX/static-assert.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/static-assert.cpp?rev=348239&r1=348238&r2=348239&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/static-assert.cpp (original)
+++ cfe/trunk/test/SemaCXX/static-assert.cpp Mon Dec 3 23:59:57 2018
@@ -68,3 +68,100 @@ template<typename T> struct second_trait
};
static_assert(first_trait<X>::value && second_trait<X>::value, "message"); // expected-error{{static_assert failed due to requirement 'second_trait<X>::value' "message"}}
+
+namespace std {
+
+template <class Tp, Tp v>
+struct integral_constant {
+ static const Tp value = v;
+ typedef Tp value_type;
+ typedef integral_constant type;
+};
+
+template <class Tp, Tp v>
+const Tp integral_constant<Tp, v>::value;
+
+typedef integral_constant<bool, true> true_type;
+typedef integral_constant<bool, false> false_type;
+
+template <class Tp>
+struct is_const : public false_type {};
+template <class Tp>
+struct is_const<Tp const> : public true_type {};
+
+// We do not define is_same in terms of integral_constant to check that both implementations are supported.
+template <typename T, typename U>
+struct is_same {
+ static const bool value = false;
+};
+
+template <typename T>
+struct is_same<T, T> {
+ static const bool value = true;
+};
+
+} // namespace std
+
+struct ExampleTypes {
+ using T = int;
+ using U = float;
+};
+
+static_assert(std::is_same<ExampleTypes::T, ExampleTypes::U>::value, "message");
+// expected-error at -1{{static_assert failed due to requirement 'std::is_same<int, float>::value' "message"}}
+static_assert(std::is_const<ExampleTypes::T>::value, "message");
+// expected-error at -1{{static_assert failed due to requirement 'std::is_const<int>::value' "message"}}
+
+struct BI_tag {};
+struct RAI_tag : BI_tag {};
+struct MyIterator {
+ using tag = BI_tag;
+};
+struct MyContainer {
+ using iterator = MyIterator;
+};
+template <class Container>
+void foo() {
+ static_assert(std::is_same<RAI_tag, typename Container::iterator::tag>::value, "message");
+ // expected-error at -1{{static_assert failed due to requirement 'std::is_same<RAI_tag, BI_tag>::value' "message"}}
+}
+template void foo<MyContainer>();
+// expected-note at -1{{in instantiation of function template specialization 'foo<MyContainer>' requested here}}
+
+namespace ns {
+template <typename T, int v>
+struct NestedTemplates1 {
+ struct NestedTemplates2 {
+ template <typename U>
+ struct NestedTemplates3 : public std::is_same<T, U> {};
+ };
+};
+} // namespace ns
+
+template <typename T, typename U, int a>
+void foo2() {
+ static_assert(::ns::NestedTemplates1<T, a>::NestedTemplates2::template NestedTemplates3<U>::value, "message");
+ // expected-error at -1{{static_assert failed due to requirement '::ns::NestedTemplates1<int, 3>::NestedTemplates2::NestedTemplates3<float>::value' "message"}}
+}
+template void foo2<int, float, 3>();
+// expected-note at -1{{in instantiation of function template specialization 'foo2<int, float, 3>' requested here}}
+
+template <class T>
+void foo3(T t) {
+ static_assert(std::is_const<T>::value, "message");
+ // expected-error-re at -1{{static_assert failed due to requirement 'std::is_const<(lambda at {{.*}}static-assert.cpp:{{[0-9]*}}:{{[0-9]*}})>::value' "message"}}
+ static_assert(std::is_const<decltype(t)>::value, "message");
+ // expected-error-re at -1{{static_assert failed due to requirement 'std::is_const<(lambda at {{.*}}static-assert.cpp:{{[0-9]*}}:{{[0-9]*}})>::value' "message"}}
+}
+void callFoo3() {
+ foo3([]() {});
+ // expected-note at -1{{in instantiation of function template specialization 'foo3<(lambda at }}
+}
+
+template <class T>
+void foo4(T t) {
+ static_assert(std::is_const<typename T::iterator>::value, "message");
+ // expected-error at -1{{type 'int' cannot be used prior to '::' because it has no members}}
+}
+void callFoo4() { foo4(42); }
+// expected-note at -1{{in instantiation of function template specialization 'foo4<int>' requested here}}
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