[clang] 0e0e8b6 - Do not evaluate dependent immediate invocations

[Utkarsh Saxena via cfe-commits]

Author: Utkarsh Saxena
Date: 2022-08-18T10:30:40+02:00
New Revision: 0e0e8b65765e32776a5188e96d1672baeb11b16c

URL: https://github.com/llvm/llvm-project/commit/0e0e8b65765e32776a5188e96d1672baeb11b16c
DIFF: https://github.com/llvm/llvm-project/commit/0e0e8b65765e32776a5188e96d1672baeb11b16c.diff

LOG: Do not evaluate dependent immediate invocations

We deferred the evaluation of dependent immediate invocations in https://reviews.llvm.org/D119375 until instantiation.
We should also not consider them referenced from a non-consteval context.

Fixes: https://github.com/llvm/llvm-project/issues/55601

```
template<typename T>
class Bar {
  consteval static T x() { return 5; }
 public:
  Bar() : a(x()) {}

 private:
  int a;
};

Bar<int> g();
```
Is now accepted by clang. Previously it errored with: `cannot take address of consteval function 'x' outside of an immediate invocation  Bar() : a(x()) {}`

Differential Revision: https://reviews.llvm.org/D132031

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Sema/SemaExpr.cpp
    clang/test/SemaCXX/cxx2a-consteval.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 4a6c9deb0c9c2..f74af34abea99 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -159,6 +159,8 @@ C++20 Feature Support
   template instantiation to be constexpr/consteval even though a call to such
   a function cannot appear in a constant expression.
   (C++14 [dcl.constexpr]p6 (CWG DR647/CWG DR1358))
+- Correctly defer dependent immediate function invocations until template instantiation.
+  This fixes `GH55601 <https://github.com/llvm/llvm-project/issues/55601>`_.
 
 
 

diff  --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 48a00f9de671c..377bfaa5f177d 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -19676,7 +19676,8 @@ void Sema::MarkDeclRefReferenced(DeclRefExpr *E, const Expr *Base) {
 
   if (auto *FD = dyn_cast<FunctionDecl>(E->getDecl()))
     if (!isUnevaluatedContext() && !isConstantEvaluated() &&
-        FD->isConsteval() && !RebuildingImmediateInvocation)
+        FD->isConsteval() && !RebuildingImmediateInvocation &&
+        !FD->isDependentContext())
       ExprEvalContexts.back().ReferenceToConsteval.insert(E);
   MarkExprReferenced(*this, E->getLocation(), E->getDecl(), E, OdrUse,
                      RefsMinusAssignments);

diff  --git a/clang/test/SemaCXX/cxx2a-consteval.cpp b/clang/test/SemaCXX/cxx2a-consteval.cpp
index 4251d82c17e60..78011e2003417 100644
--- a/clang/test/SemaCXX/cxx2a-consteval.cpp
+++ b/clang/test/SemaCXX/cxx2a-consteval.cpp
@@ -648,9 +648,40 @@ template <typename T> constexpr int baz() {
 
 static_assert(bar<15>() == 15);
 static_assert(baz<int>() == sizeof(int));
-
 } // namespace value_dependent
 
+// https://github.com/llvm/llvm-project/issues/55601
+namespace issue_55601 {
+template<typename T>
+class Bar {
+  consteval static T x() { return 5; }  // expected-note {{non-constexpr constructor 'derp' cannot be used in a constant expression}}
+ public:
+  Bar() : a(x()) {} // expected-error {{call to consteval function 'issue_55601::Bar<issue_55601::derp>::x' is not a constant expression}}
+                    // expected-error at -1 {{call to consteval function 'issue_55601::derp::operator int' is not a constant expression}}
+                    // expected-note at -2 {{in call to 'x()'}}
+                    // expected-note at -3 {{non-literal type 'issue_55601::derp' cannot be used in a constant expression}}
+ private:
+  int a;
+};
+Bar<int> f;
+Bar<float> g;
+
+struct derp {
+  // Can't be used in a constant expression
+  derp(int); // expected-note {{declared here}}
+  consteval operator int() const { return 5; }
+};
+Bar<derp> a; // expected-note {{in instantiation of member function 'issue_55601::Bar<issue_55601::derp>::Bar' requested here}}
+
+struct constantDerp {
+  // Can be used in a constant expression.
+  consteval constantDerp(int) {} 
+  consteval operator int() const { return 5; }
+};
+Bar<constantDerp> b;
+
+} // namespace issue_55601
+
 namespace default_argument {
 
 // Previously calls of consteval functions in default arguments were rejected.