Update function pointer call error message

It now uses the type of context. (issue 97082)

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -89,7 +89,10 @@ impl<'tcx> NonConstOp<'tcx> for FnCallIndirect {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        ccx.tcx.sess.struct_span_err(span, "function pointers are not allowed in const fn")
+        ccx.tcx.sess.struct_span_err(
+            span,
+            &format!("function pointer calls are not allowed in {}s", ccx.const_kind()),
+        )
     }
 }
 

src/test/ui/consts/issue-56164.stderr

@@ -7,7 +7,7 @@ LL | const fn foo() { (||{})() }
    = note: closures need an RFC before allowed to be called in constant functions
    = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
-error: function pointers are not allowed in const fn
+error: function pointer calls are not allowed in constant functions
   --> $DIR/issue-56164.rs:7:5
    |
 LL |     input()