add testcase for 34123

Fixes rust-lang#34123

Author: matthiaskrgr

src/test/ui/intrinsic_ice.rs

@@ -0,0 +1,9 @@
+// Test for https://github.com/rust-lang/rust/issues/34123
+// ICE: intrinsic .. being reified
+
+#![feature(intrinsics)]
+
+fn main(){
+    let transmute = std::intrinsics::transmute;
+    let assign: unsafe extern "rust-intrinsic" fn(*const i32) -> *mut i32 = transmute;
+}

src/test/ui/intrinsic_ice.stderr

@@ -0,0 +1,18 @@
+error[E0308]: cannot coerce intrinsics to function pointers
+ --> intrinsic_ice.rs:8:77
+  |
+L |     let assign: unsafe extern "rust-intrinsic" fn(*const i32) -> *mut i32 = transmute;
+  |                 ---------------------------------------------------------   ^^^^^^^^^ cannot coerce intrinsics to function pointers
+  |                 |
+  |                 expected due to this
+  |
+  = note: expected fn pointer `unsafe extern "rust-intrinsic" fn(*const i32) -> *mut i32`
+                found fn item `unsafe extern "rust-intrinsic" fn(_) -> _ {transmute::<_, _>}`
+help: use parentheses to call this function
+  |
+L |     let assign: unsafe extern "rust-intrinsic" fn(*const i32) -> *mut i32 = transmute(...);
+  |                                                                                      ^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.