rustc_builtin_macros: remove ref patterns

... and other pattern matching improvements

compiler/rustc_builtin_macros/src/alloc_error_handler.rs

@@ -17,32 +17,23 @@ pub fn expand(
     check_builtin_macro_attribute(ecx, meta_item, sym::alloc_error_handler);
 
     let orig_item = item.clone();
-    let not_function = || {
-        ecx.sess
-            .parse_sess
-            .span_diagnostic
-            .span_err(item.span(), "alloc_error_handler must be a function");
-        vec![orig_item.clone()]
-    };
 
     // Allow using `#[alloc_error_handler]` on an item statement
     // FIXME - if we get deref patterns, use them to reduce duplication here
-    let (item, is_stmt, sig_span) = match &item {
-        Annotatable::Item(item) => match item.kind {
-            ItemKind::Fn(ref fn_kind) => (item, false, ecx.with_def_site_ctxt(fn_kind.sig.span)),
-            _ => return not_function(),
-        },
-        Annotatable::Stmt(stmt) => match &stmt.kind {
-            StmtKind::Item(item_) => match item_.kind {
-                ItemKind::Fn(ref fn_kind) => {
-                    (item_, true, ecx.with_def_site_ctxt(fn_kind.sig.span))
-                }
-                _ => return not_function(),
-            },
-            _ => return not_function(),
-        },
-        _ => return not_function(),
-    };
+    let (item, is_stmt, sig_span) =
+        if let Annotatable::Item(item) = &item
+            && let ItemKind::Fn(fn_kind) = &item.kind
+        {
+            (item, false, ecx.with_def_site_ctxt(fn_kind.sig.span))
+        } else if let Annotatable::Stmt(stmt) = &item
+            && let StmtKind::Item(item) = &stmt.kind
+            && let ItemKind::Fn(fn_kind) = &item.kind
+        {
+            (item, true, ecx.with_def_site_ctxt(fn_kind.sig.span))
+        } else {
+            ecx.sess.parse_sess.span_diagnostic.span_err(item.span(), "alloc_error_handler must be a function");
+            return vec![orig_item.clone()];
+        };
 
     // Generate a bunch of new items using the AllocFnFactory
     let span = ecx.with_def_site_ctxt(item.span);

compiler/rustc_builtin_macros/src/assert/context.rs

@@ -191,19 +191,19 @@ impl<'cx, 'a> Context<'cx, 'a> {
     ///
     /// See [Self::manage_initial_capture] and [Self::manage_try_capture]
     fn manage_cond_expr(&mut self, expr: &mut P<Expr>) {
-        match (*expr).kind {
-            ExprKind::AddrOf(_, mutability, ref mut local_expr) => {
+        match &mut expr.kind {
+            ExprKind::AddrOf(_, mutability, local_expr) => {
                 self.with_is_consumed_management(
                     matches!(mutability, Mutability::Mut),
                     |this| this.manage_cond_expr(local_expr)
                 );
             }
-            ExprKind::Array(ref mut local_exprs) => {
+            ExprKind::Array(local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Binary(ref op, ref mut lhs, ref mut rhs) => {
+            ExprKind::Binary(op, lhs, rhs) => {
                 self.with_is_consumed_management(
                     matches!(
                         op.node,
@@ -226,56 +226,56 @@ impl<'cx, 'a> Context<'cx, 'a> {
                     }
                 );
             }
-            ExprKind::Call(_, ref mut local_exprs) => {
+            ExprKind::Call(_, local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Cast(ref mut local_expr, _) => {
+            ExprKind::Cast(local_expr, _) => {
                 self.manage_cond_expr(local_expr);
             }
-            ExprKind::Index(ref mut prefix, ref mut suffix) => {
+            ExprKind::Index(prefix, suffix) => {
                 self.manage_cond_expr(prefix);
                 self.manage_cond_expr(suffix);
             }
-            ExprKind::MethodCall(ref mut call) => {
-                for arg in call.args.iter_mut() {
+            ExprKind::MethodCall(call) => {
+                for arg in &mut call.args {
                     self.manage_cond_expr(arg);
                 }
             }
-            ExprKind::Path(_, Path { ref segments, .. }) if let &[ref path_segment] = &segments[..] => {
+            ExprKind::Path(_, Path { segments, .. }) if let [path_segment] = &segments[..] => {
                 let path_ident = path_segment.ident;
                 self.manage_initial_capture(expr, path_ident);
             }
-            ExprKind::Paren(ref mut local_expr) => {
+            ExprKind::Paren(local_expr) => {
                 self.manage_cond_expr(local_expr);
             }
-            ExprKind::Range(ref mut prefix, ref mut suffix, _) => {
-                if let Some(ref mut elem) = prefix {
+            ExprKind::Range(prefix, suffix, _) => {
+                if let Some(elem) = prefix {
                     self.manage_cond_expr(elem);
                 }
-                if let Some(ref mut elem) = suffix {
+                if let Some(elem) = suffix {
                     self.manage_cond_expr(elem);
                 }
             }
-            ExprKind::Repeat(ref mut local_expr, ref mut elem) => {
+            ExprKind::Repeat(local_expr, elem) => {
                 self.manage_cond_expr(local_expr);
                 self.manage_cond_expr(&mut elem.value);
             }
-            ExprKind::Struct(ref mut elem) => {
+            ExprKind::Struct(elem) => {
                 for field in &mut elem.fields {
                     self.manage_cond_expr(&mut field.expr);
                 }
-                if let StructRest::Base(ref mut local_expr) = elem.rest {
+                if let StructRest::Base(local_expr) = &mut elem.rest {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Tup(ref mut local_exprs) => {
+            ExprKind::Tup(local_exprs) => {
                 for local_expr in local_exprs {
                     self.manage_cond_expr(local_expr);
                 }
             }
-            ExprKind::Unary(un_op, ref mut local_expr) => {
+            ExprKind::Unary(un_op, local_expr) => {
                 self.with_is_consumed_management(
                     matches!(un_op, UnOp::Neg | UnOp::Not),
                     |this| this.manage_cond_expr(local_expr)

compiler/rustc_builtin_macros/src/concat.rs

@@ -20,7 +20,7 @@ pub fn expand_concat(
     for e in es {
         match e.kind {
             ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
-                Ok(ast::LitKind::Str(ref s, _) | ast::LitKind::Float(ref s, _)) => {
+                Ok(ast::LitKind::Str(s, _) | ast::LitKind::Float(s, _)) => {
                     accumulator.push_str(s.as_str());
                 }
                 Ok(ast::LitKind::Char(c)) => {

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -144,8 +144,8 @@ pub fn expand_concat_bytes(
     let mut missing_literals = vec![];
     let mut has_errors = false;
     for e in es {
-        match e.kind {
-            ast::ExprKind::Array(ref exprs) => {
+        match &e.kind {
+            ast::ExprKind::Array(exprs) => {
                 for expr in exprs {
                     if let Some(elem) =
                         handle_array_element(cx, &mut has_errors, &mut missing_literals, expr)
@@ -154,7 +154,7 @@ pub fn expand_concat_bytes(
                     }
                 }
             }
-            ast::ExprKind::Repeat(ref expr, ref count) => {
+            ast::ExprKind::Repeat(expr, count) => {
                 if let ast::ExprKind::Lit(token_lit) = count.value.kind
                 && let Ok(ast::LitKind::Int(count_val, _)) =
                     ast::LitKind::from_token_lit(token_lit)
@@ -170,7 +170,7 @@ pub fn expand_concat_bytes(
                     cx.span_err(count.value.span, "repeat count is not a positive number");
                 }
             }
-            ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
+            &ast::ExprKind::Lit(token_lit) => match ast::LitKind::from_token_lit(token_lit) {
                 Ok(ast::LitKind::Byte(val)) => {
                     accumulator.push(val);
                 }
@@ -184,7 +184,7 @@ pub fn expand_concat_bytes(
                     has_errors = true;
                 }
             },
-            ast::ExprKind::IncludedBytes(ref bytes) => {
+            ast::ExprKind::IncludedBytes(bytes) => {
                 accumulator.extend_from_slice(bytes);
             }
             ast::ExprKind::Err => {

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -32,10 +32,10 @@ pub fn expand_deriving_clone(
     let bounds;
     let substructure;
     let is_simple;
-    match *item {
-        Annotatable::Item(ref annitem) => match annitem.kind {
-            ItemKind::Struct(_, Generics { ref params, .. })
-            | ItemKind::Enum(_, Generics { ref params, .. }) => {
+    match item {
+        Annotatable::Item(annitem) => match &annitem.kind {
+            ItemKind::Struct(_, Generics { params, .. })
+            | ItemKind::Enum(_, Generics { params, .. }) => {
                 let container_id = cx.current_expansion.id.expn_data().parent.expect_local();
                 let has_derive_copy = cx.resolver.has_derive_copy(container_id);
                 if has_derive_copy
@@ -166,13 +166,13 @@ fn cs_clone(
     };
 
     let vdata;
-    match *substr.fields {
-        Struct(vdata_, ref af) => {
+    match substr.fields {
+        Struct(vdata_, af) => {
             ctor_path = cx.path(trait_span, vec![substr.type_ident]);
             all_fields = af;
-            vdata = vdata_;
+            vdata = *vdata_;
         }
-        EnumMatching(.., variant, ref af) => {
+        EnumMatching(.., variant, af) => {
             ctor_path = cx.path(trait_span, vec![substr.type_ident, variant.ident]);
             all_fields = af;
             vdata = &variant.data;

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -78,11 +78,11 @@ fn decodable_substructure(
     let blkarg = Ident::new(sym::_d, trait_span);
     let blkdecoder = cx.expr_ident(trait_span, blkarg);
 
-    let expr = match *substr.fields {
-        StaticStruct(_, ref summary) => {
-            let nfields = match *summary {
-                Unnamed(ref fields, _) => fields.len(),
-                Named(ref fields) => fields.len(),
+    let expr = match substr.fields {
+        StaticStruct(_, summary) => {
+            let nfields = match summary {
+                Unnamed(fields, _) => fields.len(),
+                Named(fields) => fields.len(),
             };
             let fn_read_struct_field_path: Vec<_> =
                 cx.def_site_path(&[sym::rustc_serialize, sym::Decoder, sym::read_struct_field]);
@@ -119,7 +119,7 @@ fn decodable_substructure(
                 ],
             )
         }
-        StaticEnum(_, ref fields) => {
+        StaticEnum(_, fields) => {
             let variant = Ident::new(sym::i, trait_span);
 
             let mut arms = Vec::with_capacity(fields.len() + 1);
@@ -194,10 +194,10 @@ fn decode_static_fields<F>(
 where
     F: FnMut(&mut ExtCtxt<'_>, Span, Symbol, usize) -> P<Expr>,
 {
-    match *fields {
-        Unnamed(ref fields, is_tuple) => {
+    match fields {
+        Unnamed(fields, is_tuple) => {
             let path_expr = cx.expr_path(outer_pat_path);
-            if !is_tuple {
+            if !*is_tuple {
                 path_expr
             } else {
                 let fields = fields
@@ -209,7 +209,7 @@ where
                 cx.expr_call(trait_span, path_expr, fields)
             }
         }
-        Named(ref fields) => {
+        Named(fields) => {
             // use the field's span to get nicer error messages.
             let fields = fields
                 .iter()

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -62,15 +62,12 @@ fn default_struct_substructure(
     let default_call = |span| cx.expr_call_global(span, default_ident.clone(), Vec::new());
 
     let expr = match summary {
-        Unnamed(ref fields, is_tuple) => {
-            if !is_tuple {
-                cx.expr_ident(trait_span, substr.type_ident)
-            } else {
-                let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
-                cx.expr_call_ident(trait_span, substr.type_ident, exprs)
-            }
+        Unnamed(_, false) => cx.expr_ident(trait_span, substr.type_ident),
+        Unnamed(fields, true) => {
+            let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
+            cx.expr_call_ident(trait_span, substr.type_ident, exprs)
         }
-        Named(ref fields) => {
+        Named(fields) => {
             let default_fields = fields
                 .iter()
                 .map(|&(ident, span)| cx.field_imm(span, ident, default_call(span)))

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -164,8 +164,8 @@ fn encodable_substructure(
         ],
     ));
 
-    match *substr.fields {
-        Struct(_, ref fields) => {
+    match substr.fields {
+        Struct(_, fields) => {
             let fn_emit_struct_field_path =
                 cx.def_site_path(&[sym::rustc_serialize, sym::Encoder, sym::emit_struct_field]);
             let mut stmts = Vec::new();
@@ -224,7 +224,7 @@ fn encodable_substructure(
             BlockOrExpr::new_expr(expr)
         }
 
-        EnumMatching(idx, _, variant, ref fields) => {
+        EnumMatching(idx, _, variant, fields) => {
             // We're not generating an AST that the borrow checker is expecting,
             // so we need to generate a unique local variable to take the
             // mutable loan out on, otherwise we get conflicts which don't
@@ -274,7 +274,7 @@ fn encodable_substructure(
                 vec![
                     blkencoder,
                     name,
-                    cx.expr_usize(trait_span, idx),
+                    cx.expr_usize(trait_span, *idx),
                     cx.expr_usize(trait_span, fields.len()),
                     blk,
                 ],