From 56649bb844ebf3d1861b3ee1d2616ccd22aab851 Mon Sep 17 00:00:00 2001
From: mbartlett21 <mjmouse9999@gmail.com>
Date: Tue, 17 May 2022 04:11:18 +0000
Subject: [PATCH 1/2] 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 | 5 ++++-
 src/test/ui/consts/issue-56164.stderr                       | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
index 122471b208d..4e71baa77b0 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
@@ -89,7 +89,10 @@ fn build_error(
         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()),
+        )
     }
 }
 
diff --git a/src/test/ui/consts/issue-56164.stderr b/src/test/ui/consts/issue-56164.stderr
index b997aff0e83..3b80b3486a8 100644
--- a/src/test/ui/consts/issue-56164.stderr
+++ b/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()

From cdc12edb4c18aadad2e24d1f988a30bcb17964bb Mon Sep 17 00:00:00 2001
From: mbartlett21 <mjmouse9999@gmail.com>
Date: Tue, 17 May 2022 07:24:47 +0000
Subject: [PATCH 2/2] Add a test for fn pointer calls in consts

---
 src/test/ui/consts/const-fn-ptr.rs     | 16 ++++++++++++++++
 src/test/ui/consts/const-fn-ptr.stderr | 20 ++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 src/test/ui/consts/const-fn-ptr.rs
 create mode 100644 src/test/ui/consts/const-fn-ptr.stderr

diff --git a/src/test/ui/consts/const-fn-ptr.rs b/src/test/ui/consts/const-fn-ptr.rs
new file mode 100644
index 00000000000..b1befdf06af
--- /dev/null
+++ b/src/test/ui/consts/const-fn-ptr.rs
@@ -0,0 +1,16 @@
+const fn make_fn_ptr() -> fn() {
+    || {}
+}
+
+static STAT: () = make_fn_ptr()();
+//~^ ERROR function pointer
+
+const CONST: () = make_fn_ptr()();
+//~^ ERROR function pointer
+
+const fn call_ptr() {
+    make_fn_ptr()();
+    //~^ ERROR function pointer
+}
+
+fn main() {}
diff --git a/src/test/ui/consts/const-fn-ptr.stderr b/src/test/ui/consts/const-fn-ptr.stderr
new file mode 100644
index 00000000000..84b02a25ec8
--- /dev/null
+++ b/src/test/ui/consts/const-fn-ptr.stderr
@@ -0,0 +1,20 @@
+error: function pointer calls are not allowed in statics
+  --> $DIR/const-fn-ptr.rs:5:19
+   |
+LL | static STAT: () = make_fn_ptr()();
+   |                   ^^^^^^^^^^^^^^^
+
+error: function pointer calls are not allowed in constants
+  --> $DIR/const-fn-ptr.rs:8:19
+   |
+LL | const CONST: () = make_fn_ptr()();
+   |                   ^^^^^^^^^^^^^^^
+
+error: function pointer calls are not allowed in constant functions
+  --> $DIR/const-fn-ptr.rs:12:5
+   |
+LL |     make_fn_ptr()();
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+