================
@@ -406,39 +406,41 @@ namespace PR42362 {
 namespace QualConv {
   int *X;
   template<const int *const *P> void f() {
-    using T = decltype(P);
-    using T = const int* const*;
+    using T = decltype(P);       // expected-note  {{previous definition}}
+    using T = const int* const*; // expected-error {{redefinition with 
different types ('const int *const *' vs 'decltype(P)' (aka 'const int *const 
*'))}}
   }
   template void f<&X>();
 
   template<const int *const &R> void g() {
-    using T = decltype(R);
-    using T = const int *const &;
+    using T = decltype(R);        // expected-note  {{previous definition}}
+    using T = const int *const &; // expected-error {{redefinition with 
different types ('const int *const &' vs 'decltype(R)' (aka 'const int *const 
&'))}}
   }
   template void g<(const int *const&)X>();
 }
 
 namespace FunctionConversion {
   struct a { void c(char *) noexcept; };
   template<void (a::*f)(char*)> void g() {
-    using T = decltype(f);
+    using T = decltype(f);        // expected-note  {{previous definition}}
     using T = void (a::*)(char*); // (not 'noexcept')
+    // expected-error@-1 {{redefinition with different types ('void 
(a::*)(char *)' vs 'decltype(f)' (aka 'void (a::*)(char *)'))}}
   }
   template void g<&a::c>();
 
   void c() noexcept;
   template<void (*p)()> void h() {
-    using T = decltype(p);
+    using T = decltype(p);// expected-note  {{previous definition}}
     using T = void (*)(); // (not 'noexcept')
+    // expected-error@-1 {{redefinition with different types ('void (*)()' vs 
'decltype(p)' (aka 'void (*)()'))}}
   }
   template void h<&c>();
 }
 
 namespace VoidPtr {
   // Note, this is an extension in C++17 but valid in C++20.
   template<void *P> void f() {
-    using T = decltype(P);
-    using T = void*;
+    using T = decltype(P); // expected-note  {{previous definition}}
+    using T = void*;       // expected-error {{redefinition with different 
types ('void *' vs 'decltype(P)' (aka 'void *'))}}
----------------
mizvekov wrote:

Another example: https://compiler-explorer.com/z/nGbjYsbEs
```C++
template<int V> struct A {
    static int f;
};
template<int V> decltype(V) A<V>::f = 0;
```

That's not a bug, in this context, 'decltype(P)' shouldn't be desugared to int.

I don't think the quote means this is "a syntactic element" necessarily, and 
that even if that were true, it would imply your conclusion.

The quote is used to disambiguate whatever we are trying to quote from the rest 
of the prose, as in some cases we can try to refer to something that looks like 
english text, and that would make it hard to read. 

https://github.com/llvm/llvm-project/pull/190495
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