Auto merge of rust-lang#83312 - petrochenkov:noinner, r=Aaron1011

parser: Remove support for inner attributes on non-block expressions

Remove support for attributes like
```rust
fn attrs() {
    (#![print_target_and_args(fifth)] 1, 2);

    [#![print_target_and_args(sixth)] 1 , 2];
    [#![print_target_and_args(seventh)] true ; 5];

    match 0 {
        #![print_target_and_args(eighth)]
        _ => {}
    }

    MyStruct { #![print_target_and_args(ninth)] field: true };
}
```
They are
- useless
- unstable (modulo holes like rust-lang#65860)
- pessimize compiler performance, namely token collection for macros (cc rust-lang#82608)

I still want to run crater on this to check whether the stability holes are exploited in practice, and whether such attributes are used at all.

Author: bors

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -366,10 +366,6 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
         self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, true)
     }
 
-    fn print_inner_attributes_no_trailing_hardbreak(&mut self, attrs: &[ast::Attribute]) {
-        self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, false)
-    }
-
     fn print_outer_attributes(&mut self, attrs: &[ast::Attribute]) {
         self.print_either_attributes(attrs, ast::AttrStyle::Outer, false, true)
     }
@@ -1675,32 +1671,24 @@ impl<'a> State<'a> {
         }
     }
 
-    fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>], attrs: &[ast::Attribute]) {
+    fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>]) {
         self.ibox(INDENT_UNIT);
         self.s.word("[");
-        self.print_inner_attributes_inline(attrs);
         self.commasep_exprs(Inconsistent, exprs);
         self.s.word("]");
         self.end();
     }
 
-    fn print_expr_anon_const(&mut self, expr: &ast::AnonConst, attrs: &[ast::Attribute]) {
+    fn print_expr_anon_const(&mut self, expr: &ast::AnonConst) {
         self.ibox(INDENT_UNIT);
         self.s.word("const");
-        self.print_inner_attributes_inline(attrs);
         self.print_expr(&expr.value);
         self.end();
     }
 
-    fn print_expr_repeat(
-        &mut self,
-        element: &ast::Expr,
-        count: &ast::AnonConst,
-        attrs: &[ast::Attribute],
-    ) {
+    fn print_expr_repeat(&mut self, element: &ast::Expr, count: &ast::AnonConst) {
         self.ibox(INDENT_UNIT);
         self.s.word("[");
-        self.print_inner_attributes_inline(attrs);
         self.print_expr(element);
         self.word_space(";");
         self.print_expr(&count.value);
@@ -1713,11 +1701,9 @@ impl<'a> State<'a> {
         path: &ast::Path,
         fields: &[ast::ExprField],
         rest: &ast::StructRest,
-        attrs: &[ast::Attribute],
     ) {
         self.print_path(path, true, 0);
         self.s.word("{");
-        self.print_inner_attributes_inline(attrs);
         self.commasep_cmnt(
             Consistent,
             fields,
@@ -1752,9 +1738,8 @@ impl<'a> State<'a> {
         self.s.word("}");
     }
 
-    fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>], attrs: &[ast::Attribute]) {
+    fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>]) {
         self.popen();
-        self.print_inner_attributes_inline(attrs);
         self.commasep_exprs(Inconsistent, exprs);
         if exprs.len() == 1 {
             self.s.word(",");
@@ -1865,19 +1850,19 @@ impl<'a> State<'a> {
                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
             }
             ast::ExprKind::Array(ref exprs) => {
-                self.print_expr_vec(&exprs[..], attrs);
+                self.print_expr_vec(exprs);
             }
             ast::ExprKind::ConstBlock(ref anon_const) => {
-                self.print_expr_anon_const(anon_const, attrs);
+                self.print_expr_anon_const(anon_const);
             }
             ast::ExprKind::Repeat(ref element, ref count) => {
-                self.print_expr_repeat(element, count, attrs);
+                self.print_expr_repeat(element, count);
             }
             ast::ExprKind::Struct(ref se) => {
-                self.print_expr_struct(&se.path, &se.fields, &se.rest, attrs);
+                self.print_expr_struct(&se.path, &se.fields, &se.rest);
             }
             ast::ExprKind::Tup(ref exprs) => {
-                self.print_expr_tup(&exprs[..], attrs);
+                self.print_expr_tup(exprs);
             }
             ast::ExprKind::Call(ref func, ref args) => {
                 self.print_expr_call(func, &args[..]);
@@ -1955,7 +1940,6 @@ impl<'a> State<'a> {
                 self.print_expr_as_cond(expr);
                 self.s.space();
                 self.bopen();
-                self.print_inner_attributes_no_trailing_hardbreak(attrs);
                 for arm in arms {
                     self.print_arm(arm);
                 }
@@ -2253,7 +2237,6 @@ impl<'a> State<'a> {
             ast::ExprKind::MacCall(ref m) => self.print_mac(m),
             ast::ExprKind::Paren(ref e) => {
                 self.popen();
-                self.print_inner_attributes_inline(attrs);
                 self.print_expr(e);
                 self.pclose();
             }

compiler/rustc_parse/src/parser/expr.rs

@@ -1216,10 +1216,9 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_tuple_parens_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+    fn parse_tuple_parens_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
         self.expect(&token::OpenDelim(token::Paren))?;
-        attrs.extend(self.parse_inner_attributes()?); // `(#![foo] a, b, ...)` is OK.
         let (es, trailing_comma) = match self.parse_seq_to_end(
             &token::CloseDelim(token::Paren),
             SeqSep::trailing_allowed(token::Comma),
@@ -1239,12 +1238,10 @@ impl<'a> Parser<'a> {
         self.maybe_recover_from_bad_qpath(expr, true)
     }
 
-    fn parse_array_or_repeat_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+    fn parse_array_or_repeat_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
         let lo = self.token.span;
         self.bump(); // `[`
 
-        attrs.extend(self.parse_inner_attributes()?);
-
         let close = &token::CloseDelim(token::Bracket);
         let kind = if self.eat(close) {
             // Empty vector
@@ -1950,7 +1947,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a `match ... { ... }` expression (`match` token already eaten).
-    fn parse_match_expr(&mut self, mut attrs: AttrVec) -> PResult<'a, P<Expr>> {
+    fn parse_match_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
         let match_span = self.prev_token.span;
         let lo = self.prev_token.span;
         let scrutinee = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
@@ -1965,7 +1962,6 @@ impl<'a> Parser<'a> {
             }
             return Err(e);
         }
-        attrs.extend(self.parse_inner_attributes()?);
 
         let mut arms: Vec<Arm> = Vec::new();
         while self.token != token::CloseDelim(token::Brace) {
@@ -2293,15 +2289,13 @@ impl<'a> Parser<'a> {
     pub(super) fn parse_struct_expr(
         &mut self,
         pth: ast::Path,
-        mut attrs: AttrVec,
+        attrs: AttrVec,
         recover: bool,
     ) -> PResult<'a, P<Expr>> {
         let mut fields = Vec::new();
         let mut base = ast::StructRest::None;
         let mut recover_async = false;
 
-        attrs.extend(self.parse_inner_attributes()?);
-
         let mut async_block_err = |e: &mut DiagnosticBuilder<'_>, span: Span| {
             recover_async = true;
             e.span_label(span, "`async` blocks are only allowed in Rust 2018 or later");

src/test/pretty/ast-stmt-expr-attr.rs

@@ -5,15 +5,15 @@ fn main() { }
 #[cfg(FALSE)]
 fn syntax() {
     let _ = #[attr] box 0;
-    let _ = #[attr] [#![attr] ];
-    let _ = #[attr] [#![attr] 0];
-    let _ = #[attr] [#![attr] 0; 0];
-    let _ = #[attr] [#![attr] 0, 0, 0];
+    let _ = #[attr] [];
+    let _ = #[attr] [0];
+    let _ = #[attr] [0; 0];
+    let _ = #[attr] [0, 0, 0];
     let _ = #[attr] foo();
     let _ = #[attr] x.foo();
-    let _ = #[attr] (#![attr] );
-    let _ = #[attr] (#![attr] #[attr] 0,);
-    let _ = #[attr] (#![attr] #[attr] 0, 0);
+    let _ = #[attr] ();
+    let _ = #[attr] (#[attr] 0,);
+    let _ = #[attr] (#[attr] 0, 0);
     let _ = #[attr] 0 + #[attr] 0;
     let _ = #[attr] 0 / #[attr] 0;
     let _ = #[attr] 0 & #[attr] 0;
@@ -43,10 +43,10 @@ fn syntax() {
                     #![attr]
                 };
     let _ =
-        #[attr] match true {
-                    #![attr]
-                            #[attr]
-                            _ => false,
+        #[attr] match true
+                    {
+                     #[attr]
+                     _ => false,
                 };
     let _ = #[attr] || #[attr] foo;
     let _ = #[attr] move || #[attr] foo;
@@ -119,10 +119,10 @@ fn syntax() {
     let _ = #[attr] foo![# ! [attr]];
     let _ = #[attr] foo! { };
     let _ = #[attr] foo! { # ! [attr] };
-    let _ = #[attr] Foo{#![attr] bar: baz,};
-    let _ = #[attr] Foo{#![attr] ..foo};
-    let _ = #[attr] Foo{#![attr] bar: baz, ..foo};
-    let _ = #[attr] (#![attr] 0);
+    let _ = #[attr] Foo{bar: baz,};
+    let _ = #[attr] Foo{..foo};
+    let _ = #[attr] Foo{bar: baz, ..foo};
+    let _ = #[attr] (0);
 
     {
         #[attr]

src/test/pretty/stmt_expr_attributes.rs

@@ -41,16 +41,9 @@ fn _3() {
 fn _4() {
 
     #[rustc_dummy]
-    match () {
-        #![rustc_dummy]
-        _ => (),
-    }
+    match () { _ => (), }
 
-    let _ =
-        #[rustc_dummy] match () {
-                           #![rustc_dummy]
-                           () => (),
-                       };
+    let _ = #[rustc_dummy] match () { () => (), };
 }
 
 fn _5() {
@@ -71,14 +64,14 @@ fn _5() {
 fn _6() {
 
     #[rustc_dummy]
-    [#![rustc_dummy] 1, 2, 3];
+    [1, 2, 3];
 
-    let _ = #[rustc_dummy] [#![rustc_dummy] 1, 2, 3];
+    let _ = #[rustc_dummy] [1, 2, 3];
 
     #[rustc_dummy]
-    [#![rustc_dummy] 1; 4];
+    [1; 4];
 
-    let _ = #[rustc_dummy] [#![rustc_dummy] 1; 4];
+    let _ = #[rustc_dummy] [1; 4];
 }
 
 struct Foo {
@@ -90,24 +83,24 @@ struct Bar(());
 fn _7() {
 
     #[rustc_dummy]
-    Foo{#![rustc_dummy] data: (),};
+    Foo{data: (),};
 
-    let _ = #[rustc_dummy] Foo{#![rustc_dummy] data: (),};
+    let _ = #[rustc_dummy] Foo{data: (),};
 }
 
 fn _8() {
 
     #[rustc_dummy]
-    (#![rustc_dummy] );
+    ();
 
     #[rustc_dummy]
-    (#![rustc_dummy] 0);
+    (0);
 
     #[rustc_dummy]
-    (#![rustc_dummy] 0,);
+    (0,);
 
     #[rustc_dummy]
-    (#![rustc_dummy] 0, 1);
+    (0, 1);
 }
 
 fn _9() {
@@ -138,15 +131,15 @@ fn _10() {
 
 fn _11() {
     let _ = #[rustc_dummy] box 0;
-    let _: [(); 0] = #[rustc_dummy] [#![rustc_dummy] ];
-    let _ = #[rustc_dummy] [#![rustc_dummy] 0, 0];
-    let _ = #[rustc_dummy] [#![rustc_dummy] 0; 0];
+    let _: [(); 0] = #[rustc_dummy] [];
+    let _ = #[rustc_dummy] [0, 0];
+    let _ = #[rustc_dummy] [0; 0];
     let _ = #[rustc_dummy] foo();
     let _ = #[rustc_dummy] 1i32.clone();
-    let _ = #[rustc_dummy] (#![rustc_dummy] );
-    let _ = #[rustc_dummy] (#![rustc_dummy] 0);
-    let _ = #[rustc_dummy] (#![rustc_dummy] 0,);
-    let _ = #[rustc_dummy] (#![rustc_dummy] 0, 0);
+    let _ = #[rustc_dummy] ();
+    let _ = #[rustc_dummy] (0);
+    let _ = #[rustc_dummy] (0,);
+    let _ = #[rustc_dummy] (0, 0);
     let _ = #[rustc_dummy] 0 + #[rustc_dummy] 0;
     let _ = #[rustc_dummy] !0;
     let _ = #[rustc_dummy] -0i32;
@@ -171,11 +164,7 @@ fn _11() {
         #[rustc_dummy] loop  {
                            #![rustc_dummy]
                        };
-    let _ =
-        #[rustc_dummy] match false {
-                           #![rustc_dummy]
-                           _ => (),
-                       };
+    let _ = #[rustc_dummy] match false { _ => (), };
     let _ = #[rustc_dummy] || #[rustc_dummy] ();
     let _ = #[rustc_dummy] move || #[rustc_dummy] ();
     let _ =
@@ -237,10 +226,10 @@ fn _11() {
     let _ = #[rustc_dummy] expr_mac!();
     let _ = #[rustc_dummy] expr_mac![];
     let _ = #[rustc_dummy] expr_mac! { };
-    let _ = #[rustc_dummy] Foo{#![rustc_dummy] data: (),};
-    let _ = #[rustc_dummy] Foo{#![rustc_dummy] ..s};
-    let _ = #[rustc_dummy] Foo{#![rustc_dummy] data: (), ..s};
-    let _ = #[rustc_dummy] (#![rustc_dummy] 0);
+    let _ = #[rustc_dummy] Foo{data: (),};
+    let _ = #[rustc_dummy] Foo{..s};
+    let _ = #[rustc_dummy] Foo{data: (), ..s};
+    let _ = #[rustc_dummy] (0);
 }
 
 fn _12() {

src/test/ui/lint/expr_attr_paren_order.rs

@@ -5,16 +5,14 @@ fn main() {
     // Test that attributes on parens get concatenated
     // in the expected order in the hir folder.
 
-    #[deny(non_snake_case)] (
-        #![allow(non_snake_case)]
+    #[deny(non_snake_case)] #[allow(non_snake_case)] (
         {
             let X = 0;
             let _ = X;
         }
     );
 
-    #[allow(non_snake_case)] (
-        #![deny(non_snake_case)]
+    #[allow(non_snake_case)] #[deny(non_snake_case)] (
         {
             let X = 0; //~ ERROR snake case name
             let _ = X;

src/test/ui/lint/expr_attr_paren_order.stderr

@@ -1,14 +1,14 @@
 error: variable `X` should have a snake case name
-  --> $DIR/expr_attr_paren_order.rs:19:17
+  --> $DIR/expr_attr_paren_order.rs:17:17
    |
 LL |             let X = 0;
    |                 ^ help: convert the identifier to snake case (notice the capitalization): `x`
    |
 note: the lint level is defined here
-  --> $DIR/expr_attr_paren_order.rs:17:17
+  --> $DIR/expr_attr_paren_order.rs:15:37
    |
-LL |         #![deny(non_snake_case)]
-   |                 ^^^^^^^^^^^^^^
+LL |     #[allow(non_snake_case)] #[deny(non_snake_case)] (
+   |                                     ^^^^^^^^^^^^^^
 
 error: aborting due to previous error