Report a diagnostic when a non-finite float constant is cast to an integer (#229)

src/fpy/semantics.py

@@ -2421,7 +2421,8 @@ def const_convert_type(
                 return FpyValue(to_type, raw_val)
 
             assert False, (from_val, from_type, to_type)
-        except (ValueError, struct.error) as e:
+        except (ValueError, OverflowError, struct.error) as e:
+            # OverflowError is int(inf); ValueError is int(nan)
             state.err(f"For type {from_type.display_name}: {e}", node)
             return None
 

test/fpy/test_arithmetic.py

@@ -56,6 +56,34 @@ def test_const_complex_pow(self, fprime_test_api):
 
         assert_compile_failure(fprime_test_api, seq)
 
+    def test_const_infinity_to_int(self, fprime_test_api):
+        """An infinite float constant cast to an integer type is a compile
+        error, not an uncaught OverflowError."""
+        seq = """
+x: I64 = I64(F64(1e308) * F64(10.0))
+exit(0)
+"""
+
+        assert_compile_failure(fprime_test_api, seq, match="infinity")
+
+    def test_const_negative_infinity_to_int(self, fprime_test_api):
+        """The same holds for a negative infinity and an unsigned target."""
+        seq = """
+x: U8 = U8(F64(-1e308) + F64(-1e308))
+exit(0)
+"""
+
+        assert_compile_failure(fprime_test_api, seq, match="infinity")
+
+    def test_const_nan_to_int(self, fprime_test_api):
+        """The NaN counterpart reports a diagnostic too."""
+        seq = """
+x: I64 = I64(F64(1e308) * F64(10.0) - F64(1e308) * F64(10.0))
+exit(0)
+"""
+
+        assert_compile_failure(fprime_test_api, seq, match="NaN")
+
     def test_very_large_const_pow(self, fprime_test_api):
         seq = """
 10.0 ** 1000