use field init shorthand EVERYWHERE

Like #43008 (f668999), but _much more aggressive_.

src/libsyntax/std_inject.rs

@@ -72,18 +72,18 @@ pub fn maybe_inject_crates_ref(mut krate: ast::Crate, alt_std_name: Option<Strin
             tokens: TokenStream::empty(),
             id: attr::mk_attr_id(),
             is_sugared_doc: false,
-            span: span,
+            span,
         }],
         vis: ast::Visibility::Inherited,
         node: ast::ItemKind::Use(P(codemap::dummy_spanned(ast::ViewPathGlob(ast::Path {
             segments: ["{{root}}", name, "prelude", "v1"].into_iter().map(|name| {
                 ast::PathSegment::from_ident(ast::Ident::from_str(name), DUMMY_SP)
             }).collect(),
-            span: span,
+            span,
         })))),
         id: ast::DUMMY_NODE_ID,
         ident: keywords::Invalid.ident(),
-        span: span,
+        span,
         tokens: None,
     }));