[Rust] fix generated comparison when value is NAN (aeron-io#895) (aeron-io#896)

Co-authored-by: Michael Ward <mward@drw.com>

Author: mward

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/rust/RustGenerator.java

@@ -746,8 +746,18 @@ private static void generatePrimitiveOptionalDecoder(
  indent(sb, level + 1, "let value = self.get_buf().get_%s_at(self.%s);\n",
  rustPrimitiveType,
  getBufOffset(fieldToken));
- indent(sb, level + 1, "if value == %s {\n",
- generateRustLiteral(primitiveType, encoding.applicableNullValue().toString()));
+
+
+ final String literal = generateRustLiteral(primitiveType, encoding.applicableNullValue().toString());
+ if (literal.endsWith("::NAN"))
+ {
+ indent(sb, level + 1, "if value.is_nan() {\n");
+ }
+ else
+ {
+ indent(sb, level + 1, "if value == %s {\n", literal);
+ }
+
  indent(sb, level + 2, "None\n");
  indent(sb, level + 1, "} else {\n");
  indent(sb, level + 2, "Some(value)\n");