[Rust] codegen of primitive enums now implement 'From' instead of 'Into' (#1029)

* [Rust] updated LibRsDef.generate() to add "#![allow(clippy::all)]"

* [Rust] generating 'From<ENUM> for PRIMITIVE' instead of 'Into<PRIMITIVE> for ENUM' to satisfy 'from_over_into' lint

* [Rust] removed unused method parameter

* fixed formatting

---------

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

Author: mward

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

@@ -60,7 +60,7 @@ void generate(final Ir ir) throws IOException
         try (Writer libRs = outputManager.createOutput("lib"))
         {
             indent(libRs, 0, "#![forbid(unsafe_code)]\n");
-            indent(libRs, 0, "#![allow(clippy::upper_case_acronyms)]\n");
+            indent(libRs, 0, "#![allow(clippy::all)]\n");
             indent(libRs, 0, "#![allow(non_camel_case_types)]\n\n");
             indent(libRs, 0, "#![allow(ambiguous_glob_reexports)]\n\n");
             indent(libRs, 0, "use ::core::{convert::TryInto};\n\n");

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

@@ -1265,19 +1265,19 @@ private static void generateEnum(
         indent(writer, 0, "}\n");
 
         // From impl
-        generateFromImplForEnum(enumRustName, primitiveType, messageBody, writer);
+        generateFromPrimitiveForEnum(enumRustName, primitiveType, messageBody, writer);
 
         // Into impl
-        generateIntoImplForEnum(enumRustName, primitiveType, messageBody, writer);
+        generateFromEnumForPrimitive(enumRustName, primitiveType, messageBody, writer);
 
         // FromStr impl
-        generateFromStrImplForEnum(enumRustName, primitiveType, messageBody, writer);
+        generateFromStrImplForEnum(enumRustName, messageBody, writer);
 
         // Display impl
         generateDisplayImplForEnum(enumRustName, primitiveType, messageBody, writer);
     }
 
-    private static void generateFromImplForEnum(
+    private static void generateFromPrimitiveForEnum(
         final String enumRustName,
         final String primitiveType,
         final List<Token> messageBody,
@@ -1302,27 +1302,29 @@ private static void generateFromImplForEnum(
         indent(writer, 0, "}\n");
     }
 
-    private static void generateIntoImplForEnum(
+    private static void generateFromEnumForPrimitive(
         final String enumRustName,
         final String primitiveType,
         final List<Token> messageBody,
         final Appendable writer) throws IOException
     {
-        indent(writer, 0, "impl Into<%s> for %s {\n", primitiveType, enumRustName);
+        indent(writer, 0, "impl From<%s> for %s {\n", enumRustName, primitiveType);
         indent(writer, 1, "#[inline]\n");
-        indent(writer, 1, "fn into(self) -> %s {\n", primitiveType);
-        indent(writer, 2, "match self {\n");
+        indent(writer, 1, "fn from(v: %s) -> Self {\n", enumRustName);
+        indent(writer, 2, "match v {\n");
+
         for (final Token token : messageBody)
         {
             final Encoding encoding = token.encoding();
             final String literal = generateRustLiteral(encoding.primitiveType(), encoding.constValue().toString());
-            indent(writer, 3, "Self::%s => %s, \n", token.name(), literal);
+            indent(writer, 3, "%s::%s => %s, \n", enumRustName, token.name(), literal);
         }
+
         {
             final Encoding encoding = messageBody.get(0).encoding();
             final CharSequence nullVal = generateRustLiteral(encoding.primitiveType(),
                 encoding.applicableNullValue().toString());
-            indent(writer, 3, "Self::NullVal => %s,\n", nullVal);
+            indent(writer, 3, "%s::NullVal => %s,\n", enumRustName, nullVal);
         }
         indent(writer, 2, "}\n");
         indent(writer, 1, "}\n");
@@ -1331,7 +1333,6 @@ private static void generateIntoImplForEnum(
 
     private static void generateFromStrImplForEnum(
         final String enumRustName,
-        final String primitiveType,
         final List<Token> messageBody,
         final Appendable writer) throws IOException
     {
@@ -1342,10 +1343,10 @@ private static void generateFromStrImplForEnum(
         indent(writer, 2, "match v {\n");
         for (final Token token : messageBody)
         {
-            indent(writer, 3, "\"%1$s\" => core::result::Result::Ok(Self::%1$s), \n", token.name());
+            indent(writer, 3, "\"%1$s\" => Ok(Self::%1$s), \n", token.name());
         }
         // default => NullVal
-        indent(writer, 3, "_ => core::result::Result::Ok(Self::NullVal),\n");
+        indent(writer, 3, "_ => Ok(Self::NullVal),\n");
         indent(writer, 2, "}\n");
         indent(writer, 1, "}\n");
         indent(writer, 0, "}\n");