Auto merge of #46187 - notriddle:patch-1, r=QuietMisdreavus

Rename C-like enum to Field-less enum

There is no need to reference the C programming language to explain this concept.

src/librustc/diagnostics.rs

@@ -1641,14 +1641,14 @@ impl Foo {
 These attributes do not work on typedefs, since typedefs are just aliases.
 
 Representations like `#[repr(u8)]`, `#[repr(i64)]` are for selecting the
-discriminant size for C-like enums (when there is no associated data, e.g.
-`enum Color {Red, Blue, Green}`), effectively setting the size of the enum to
+discriminant size for enums with no data fields on any of the variants, e.g.
+`enum Color {Red, Blue, Green}`, effectively setting the size of the enum to
 the size of the provided type. Such an enum can be cast to a value of the same
 type as well. In short, `#[repr(u8)]` makes the enum behave like an integer
 with a constrained set of allowed values.
 
-Only C-like enums can be cast to numerical primitives, so this attribute will
-not apply to structs.
+Only field-less enums can be cast to numerical primitives, so this attribute
+will not apply to structs.
 
 `#[repr(packed)]` reduces padding to make the struct size smaller. The
 representation of enums isn't strictly defined in Rust, and this attribute

src/libsyntax/parse/parser.rs

@@ -5995,7 +5995,7 @@ fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef>
         match any_disr {
             Some(disr_span) if !all_nullary =>
                 self.span_err(disr_span,
-                    "discriminator values can only be used with a c-like enum"),
+                    "discriminator values can only be used with a field-less enum"),
             _ => ()
         }
 

src/test/parse-fail/issue-17383.rs

@@ -12,7 +12,7 @@
 
 enum X {
     A =
-        b'a' //~ ERROR discriminator values can only be used with a c-like enum
+        b'a' //~ ERROR discriminator values can only be used with a field-less enum
     ,
     B(isize)
 }

src/test/parse-fail/tag-variant-disr-non-nullary.rs

@@ -10,7 +10,7 @@
 
 // compile-flags: -Z parse-only
 
-//error-pattern: discriminator values can only be used with a c-like enum
+//error-pattern: discriminator values can only be used with a field-less enum
 
 enum color {
     red = 0xff0000,