use field init shorthand EVERYWHERE

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

src/libsyntax/ast.rs

@@ -135,7 +135,7 @@ impl PathSegment {
     pub fn crate_root(span: Span) -> Self {
         PathSegment {
             identifier: Ident { ctxt: span.ctxt, ..keywords::CrateRoot.ident() },
-            span: span,
+            span,
             parameters: None,
         }
     }
@@ -1492,15 +1492,15 @@ impl Arg {
         let infer_ty = P(Ty {
             id: DUMMY_NODE_ID,
             node: TyKind::ImplicitSelf,
-            span: span,
+            span,
         });
         let arg = |mutbl, ty| Arg {
             pat: P(Pat {
                 id: DUMMY_NODE_ID,
                 node: PatKind::Ident(BindingMode::ByValue(mutbl), eself_ident, None),
-                span: span,
+                span,
             }),
-            ty: ty,
+            ty,
             id: DUMMY_NODE_ID,
         };
         match eself.node {
@@ -1509,7 +1509,7 @@ impl Arg {
             SelfKind::Region(lt, mutbl) => arg(Mutability::Immutable, P(Ty {
                 id: DUMMY_NODE_ID,
                 node: TyKind::Rptr(lt, MutTy { ty: infer_ty, mutbl: mutbl }),
-                span: span,
+                span,
             })),
         }
     }
@@ -1738,7 +1738,7 @@ impl PolyTraitRef {
         PolyTraitRef {
             bound_lifetimes: lifetimes,
             trait_ref: TraitRef { path: path, ref_id: DUMMY_NODE_ID },
-            span: span,
+            span,
         }
     }
 }