Remove token::Lit from ast::MetaItemLit.

`token::Lit` contains a `kind` field that indicates what kind of literal
it is. `ast::MetaItemLit` currently wraps a `token::Lit` but also has
its own `kind` field. This means that `ast::MetaItemLit` encodes the
literal kind in two different ways.

This commit changes `ast::MetaItemLit` so it no longer wraps
`token::Lit`. It now contains the `symbol` and `suffix` fields from
`token::Lit`, but not the `kind` field, eliminating the redundancy.

compiler/rustc_ast/src/ast.rs

@@ -1733,8 +1733,10 @@ pub enum StrStyle {
 /// A literal in a meta item.
 #[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
 pub struct MetaItemLit {
-    /// The original literal token as written in source code.
+    /// The original literal as written in the source code.
-    pub token_lit: token::Lit,
+    pub symbol: Symbol,
+    /// The original suffix as written in the source code.
+    pub suffix: Option<Symbol>,
     /// The "semantic" representation of the literal lowered from the original tokens.
     /// Strings are unescaped, hexadecimal forms are eliminated, etc.
     pub kind: LitKind,
@@ -3103,7 +3105,7 @@ mod size_asserts {
     static_assert_size!(ItemKind, 112);
     static_assert_size!(LitKind, 24);
     static_assert_size!(Local, 72);
-    static_assert_size!(MetaItemLit, 48);
+    static_assert_size!(MetaItemLit, 40);
     static_assert_size!(Param, 40);
     static_assert_size!(Pat, 88);
     static_assert_size!(Path, 24);

compiler/rustc_ast/src/attr/mod.rs

@@ -328,7 +328,9 @@ pub fn mk_name_value_item_str(ident: Ident, str: Symbol, str_span: Span) -> Meta
 }
 
 pub fn mk_name_value_item(ident: Ident, kind: LitKind, lit_span: Span) -> MetaItem {
-    let lit = MetaItemLit { token_lit: kind.synthesize_token_lit(), kind, span: lit_span };
+    let token_lit = kind.synthesize_token_lit();
+    let lit =
+        MetaItemLit { symbol: token_lit.symbol, suffix: token_lit.suffix, kind, span: lit_span };
     let span = ident.span.to(lit_span);
     MetaItem { path: Path::from_ident(ident), kind: MetaItemKind::NameValue(lit), span }
 }

compiler/rustc_ast/src/util/literal.rs

@@ -202,9 +202,32 @@ impl LitKind {
 }
 
 impl MetaItemLit {
-    /// Converts token literal into a meta item literal.
+    /// Converts a token literal into a meta item literal.
     pub fn from_token_lit(token_lit: token::Lit, span: Span) -> Result<MetaItemLit, LitError> {
-        Ok(MetaItemLit { token_lit, kind: LitKind::from_token_lit(token_lit)?, span })
+        Ok(MetaItemLit {
+            symbol: token_lit.symbol,
+            suffix: token_lit.suffix,
+            kind: LitKind::from_token_lit(token_lit)?,
+            span,
+        })
+    }
+
+    /// Cheaply converts a meta item literal into a token literal.
+    pub fn as_token_lit(&self) -> token::Lit {
+        let kind = match self.kind {
+            LitKind::Bool(_) => token::Bool,
+            LitKind::Str(_, ast::StrStyle::Cooked) => token::Str,
+            LitKind::Str(_, ast::StrStyle::Raw(n)) => token::StrRaw(n),
+            LitKind::ByteStr(_, ast::StrStyle::Cooked) => token::ByteStr,
+            LitKind::ByteStr(_, ast::StrStyle::Raw(n)) => token::ByteStrRaw(n),
+            LitKind::Byte(_) => token::Byte,
+            LitKind::Char(_) => token::Char,
+            LitKind::Int(..) => token::Integer,
+            LitKind::Float(..) => token::Float,
+            LitKind::Err => token::Err,
+        };
+
+        token::Lit::new(kind, self.symbol, self.suffix)
     }
 
     /// Converts an arbitrary token into meta item literal.

compiler/rustc_ast_lowering/src/lib.rs

@@ -954,7 +954,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     lit
                 } else {
                     MetaItemLit {
-                        token_lit: token::Lit::new(token::LitKind::Err, kw::Empty, None),
+                        symbol: kw::Empty,
+                        suffix: None,
                         kind: LitKind::Err,
                         span: DUMMY_SP,
                     }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -376,7 +376,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     }
 
     fn print_meta_item_lit(&mut self, lit: &ast::MetaItemLit) {
-        self.print_token_literal(lit.token_lit, lit.span)
+        self.print_token_literal(lit.as_token_lit(), lit.span)
     }
 
     fn print_token_literal(&mut self, token_lit: token::Lit, span: Span) {

compiler/rustc_builtin_macros/src/derive.rs

@@ -1,7 +1,7 @@
 use crate::cfg_eval::cfg_eval;
 
 use rustc_ast as ast;
-use rustc_ast::{token, GenericParamKind, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
+use rustc_ast::{GenericParamKind, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
 use rustc_errors::{struct_span_err, Applicability};
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
 use rustc_feature::AttributeTemplate;
@@ -130,9 +130,11 @@ fn report_bad_target(sess: &Session, item: &Annotatable, span: Span) -> bool {
 }
 
 fn report_unexpected_meta_item_lit(sess: &Session, lit: &ast::MetaItemLit) {
-    let help_msg = match lit.token_lit.kind {
+    let help_msg = match lit.kind {
-        token::Str if rustc_lexer::is_ident(lit.token_lit.symbol.as_str()) => {
+        ast::LitKind::Str(_, ast::StrStyle::Cooked)
-            format!("try using `#[derive({})]`", lit.token_lit.symbol)
+            if rustc_lexer::is_ident(lit.symbol.as_str()) =>
+        {
+            format!("try using `#[derive({})]`", lit.symbol)
         }
         _ => "for example, write `#[derive(Debug)]` for `Debug`".to_string(),
     };

compiler/rustc_parse/src/parser/expr.rs

@@ -1551,7 +1551,7 @@ impl<'a> Parser<'a> {
                 })
             });
             consume_colon = false;
-            Ok(self.mk_expr(lo, ExprKind::Lit(lit.token_lit)))
+            Ok(self.mk_expr(lo, ExprKind::Lit(lit.as_token_lit())))
         } else if !ate_colon
             && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
         {
@@ -1654,7 +1654,8 @@ impl<'a> Parser<'a> {
         }
         let name = lifetime.without_first_quote().name;
         ast::MetaItemLit {
-            token_lit: token::Lit::new(token::LitKind::Char, name, None),
+            symbol: name,
+            suffix: None,
             kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
             span: lifetime.span,
         }
@@ -1773,8 +1774,8 @@ impl<'a> Parser<'a> {
             Some(lit) => match lit.kind {
                 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
                     style,
-                    symbol: lit.token_lit.symbol,
+                    symbol: lit.symbol,
-                    suffix: lit.token_lit.suffix,
+                    suffix: lit.suffix,
                     span: lit.span,
                     symbol_unescaped,
                 }),
@@ -1817,7 +1818,7 @@ impl<'a> Parser<'a> {
     pub(super) fn parse_token_lit(&mut self) -> PResult<'a, (token::Lit, Span)> {
         self.parse_opt_token_lit()
             .ok_or(())
-            .or_else(|()| self.handle_missing_lit().map(|lit| (lit.token_lit, lit.span)))
+            .or_else(|()| self.handle_missing_lit().map(|lit| (lit.as_token_lit(), lit.span)))
     }
 
     pub(super) fn parse_meta_item_lit(&mut self) -> PResult<'a, MetaItemLit> {

compiler/rustc_parse/src/parser/pat.rs

@@ -420,7 +420,7 @@ impl<'a> Parser<'a> {
                 err.span_label(self_.token.span, format!("expected {}", expected));
                 err
             });
-            PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit.token_lit)))
+            PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit.as_token_lit())))
         } else {
             // Try to parse everything else as literal with optional minus
             match self.parse_literal_maybe_minus() {

src/tools/rustfmt/src/attr.rs

@@ -260,7 +260,9 @@ impl Rewrite for ast::NestedMetaItem {
     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
         match self {
             ast::NestedMetaItem::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
-            ast::NestedMetaItem::Lit(ref l) => rewrite_literal(context, l.token_lit, l.span, shape),
+            ast::NestedMetaItem::Lit(ref l) => {
+                rewrite_literal(context, l.as_token_lit(), l.span, shape)
+            }
         }
     }
 }
@@ -308,18 +310,18 @@ impl Rewrite for ast::MetaItem {
                     }),
                 )?
             }
-            ast::MetaItemKind::NameValue(ref literal) => {
+            ast::MetaItemKind::NameValue(ref lit) => {
                 let path = rewrite_path(context, PathContext::Type, &None, &self.path, shape)?;
                 // 3 = ` = `
                 let lit_shape = shape.shrink_left(path.len() + 3)?;
-                // `rewrite_literal` returns `None` when `literal` exceeds max
+                // `rewrite_literal` returns `None` when `lit` exceeds max
                 // width. Since a literal is basically unformattable unless it
                 // is a string literal (and only if `format_strings` is set),
                 // we might be better off ignoring the fact that the attribute
                 // is longer than the max width and continue on formatting.
                 // See #2479 for example.
-                let value = rewrite_literal(context, literal.token_lit, literal.span, lit_shape)
+                let value = rewrite_literal(context, lit.as_token_lit(), lit.span, lit_shape)
-                    .unwrap_or_else(|| context.snippet(literal.span).to_owned());
+                    .unwrap_or_else(|| context.snippet(lit.span).to_owned());
                 format!("{} = {}", path, value)
             }
         })