test some more extreme cast cases

Author: RalfJung

tests/compile-fail/intrinsics/float_to_int_64_too_big6.rs

@@ -0,0 +1,10 @@
+#![feature(intrinsics)]
+
+// Directly call intrinsic to avoid debug assertions in libstd
+extern "rust-intrinsic" {
+    fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+}
+
+fn main() {
+    unsafe { float_to_int_unchecked::<f64, u128>(f64::MAX); } //~ ERROR: cannot be represented in target type `u128`
+}

tests/compile-fail/intrinsics/float_to_int_64_too_big7.rs

@@ -0,0 +1,10 @@
+#![feature(intrinsics)]
+
+// Directly call intrinsic to avoid debug assertions in libstd
+extern "rust-intrinsic" {
+    fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
+}
+
+fn main() {
+    unsafe { float_to_int_unchecked::<f64, i128>(f64::MIN); } //~ ERROR: cannot be represented in target type `i128`
+}