Rollup merge of #32682 - petrochenkov:field3, r=Manishearth

 The AST part of https://github.com/rust-lang/rust/pull/31937

Unlike HIR, AST still uses `Option` for field names because parser can't know field indexes reliably due to constructions like
```
struct S(#[cfg(false)] u8, u8); // The index of the second field changes from 1 during parsing to 0 after expansion.
```
and I wouldn't like to put the burden of renaming fields on expansion passes and syntax extensions.

plugin-[breaking-change] cc https://github.com/rust-lang/rust/issues/31645
r? @Manishearth

1 files changed, 11 insertions, 21 deletions

diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index a8f28ed3d9e..e2b1d2f5e7a 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1407,14 +1407,9 @@ impl<'a> State<'a> {
                 self.commasep(
                     Inconsistent, struct_def.fields(),
                     |s, field| {
-                        match field.node.kind {
-                            ast::NamedField(..) => panic!("unexpected named field"),
-                            ast::UnnamedField(ref vis) => {
-                                s.print_visibility(vis)?;
-                                s.maybe_print_comment(field.span.lo)?;
-                                s.print_type(&field.node.ty)
-                            }
-                        }
+                        s.print_visibility(&field.vis)?;
+                        s.maybe_print_comment(field.span.lo)?;
+                        s.print_type(&field.ty)
                     }
                 )?;
                 self.pclose()?;
@@ -1432,19 +1427,14 @@ impl<'a> State<'a> {
             self.hardbreak_if_not_bol()?;
 
             for field in struct_def.fields() {
-                match field.node.kind {
-                    ast::UnnamedField(..) => panic!("unexpected unnamed field"),
-                    ast::NamedField(ident, ref visibility) => {
-                        self.hardbreak_if_not_bol()?;
-                        self.maybe_print_comment(field.span.lo)?;
-                        self.print_outer_attributes(&field.node.attrs)?;
-                        self.print_visibility(visibility)?;
-                        self.print_ident(ident)?;
-                        self.word_nbsp(":")?;
-                        self.print_type(&field.node.ty)?;
-                        word(&mut self.s, ",")?;
-                    }
-                }
+                self.hardbreak_if_not_bol()?;
+                self.maybe_print_comment(field.span.lo)?;
+                self.print_outer_attributes(&field.attrs)?;
+                self.print_visibility(&field.vis)?;
+                self.print_ident(field.ident.unwrap())?;
+                self.word_nbsp(":")?;
+                self.print_type(&field.ty)?;
+                word(&mut self.s, ",")?;
             }
 
             self.bclose(span)