transpile: Propagate cast of EnumConstant to its own integral type

Author: Rua

c2rust-transpile/src/translator/mod.rs

@@ -3601,6 +3601,18 @@ impl<'c> Translation<'c> {
                 if self.enum_constant_matches_type(target_type_id.ctype, decl_id) {
                     return true;
                 }
+
+                let source_enum_id = self.ast_context.parents[&decl_id];
+                let source_integral_type_id = self.enum_integral_type(source_enum_id);
+                let target_type_resolved_id = self
+                    .ast_context
+                    .resolve_type_id_no_typedef(target_type_id.ctype);
+
+                // Likewise, if we are casting to the inner integral type of the enum, then
+                // translate the enum constant directly as that.
+                if target_type_resolved_id == source_integral_type_id.ctype {
+                    return true;
+                }
             }
         }
 

c2rust-transpile/tests/snapshots/snapshots__transpile@enums.c.2021.clang15.snap

@@ -44,8 +44,7 @@ pub unsafe extern "C" fn test_enums() {
     bar = Bar(bar.0 - 2 as ::core::ffi::c_int);
     let mut e: Foo = Foo1;
     let mut enum_enum: ::core::ffi::c_int = (e.0 == foo.0) as ::core::ffi::c_int;
-    let mut enum_constant: ::core::ffi::c_int =
-        (e.0 == Foo0.0 as ::core::ffi::c_int as ::core::ffi::c_uint) as ::core::ffi::c_int;
+    let mut enum_constant: ::core::ffi::c_int = (e.0 == Foo0.0) as ::core::ffi::c_int;
     let mut wrong_enum_enum: ::core::ffi::c_int =
         (e.0 == bar.0 as ::core::ffi::c_uint) as ::core::ffi::c_int;
     let mut wrong_enum_constant: ::core::ffi::c_int =

c2rust-transpile/tests/snapshots/snapshots__transpile@enums.c.2024.clang15.snap

@@ -45,8 +45,7 @@ pub unsafe extern "C" fn test_enums() {
     bar = Bar(bar.0 - 2 as ::core::ffi::c_int);
     let mut e: Foo = Foo1;
     let mut enum_enum: ::core::ffi::c_int = (e.0 == foo.0) as ::core::ffi::c_int;
-    let mut enum_constant: ::core::ffi::c_int =
-        (e.0 == Foo0.0 as ::core::ffi::c_int as ::core::ffi::c_uint) as ::core::ffi::c_int;
+    let mut enum_constant: ::core::ffi::c_int = (e.0 == Foo0.0) as ::core::ffi::c_int;
     let mut wrong_enum_enum: ::core::ffi::c_int =
         (e.0 == bar.0 as ::core::ffi::c_uint) as ::core::ffi::c_int;
     let mut wrong_enum_constant: ::core::ffi::c_int =