FFI: Add test for runtime errors

tests/ffi/ffi-runtime-errors.c

@@ -0,0 +1,10 @@
+#include <stddef.h>
+#include <stdint.h>
+
+uint8_t f(size_t n, uint8_t *p) {
+  return n == 0;
+}
+
+uint8_t g(uint8_t x) {
+  return x;
+}

tests/ffi/ffi-runtime-errors.cry

@@ -0,0 +1,2 @@
+foreign f : {n} (fin n, n >= 2^^64) => [n - 2^^64][8] -> Bit
+foreign g : Bit -> Bit

tests/ffi/ffi-runtime-errors.icry

@@ -0,0 +1,9 @@
+:! make -s ffi-runtime-errors
+:l ffi-runtime-errors.cry
+
+f []
+
+:prove g
+:sat g
+:safe g
+:eval g

tests/ffi/ffi-runtime-errors.icry.stdout

@@ -0,0 +1,28 @@
+Loading module Cryptol
+Loading module Cryptol
+Loading module Main
+
+numeric type argument to foreign function is too large: 18446744073709551616
+in type parameter n`899 of function Main::f
+type arguments must fit in a C `size_t`
+-- Backtrace --
+Main::f called at ffi-runtime-errors.icry:4:1--4:2
+
+cannot call foreign function Main::g
+FFI calls are not supported in this context
+If you are trying to evaluate an expression, try rebuilding
+  Cryptol with FFI support enabled.
+
+cannot call foreign function Main::g
+FFI calls are not supported in this context
+If you are trying to evaluate an expression, try rebuilding
+  Cryptol with FFI support enabled.
+
+cannot call foreign function Main::g
+FFI calls are not supported in this context
+If you are trying to evaluate an expression, try rebuilding
+  Cryptol with FFI support enabled.
+cannot call foreign function Main::g
+FFI calls are not supported in this context
+If you are trying to evaluate an expression, try rebuilding
+  Cryptol with FFI support enabled.