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Author: Orion Gonzalez

compiler/rustc_ast_pretty/src/pprust/mod.rs

@@ -7,7 +7,7 @@ use std::borrow::Cow;
 use rustc_ast as ast;
 use rustc_ast::token::{Nonterminal, Token, TokenKind};
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
-pub use state::{AnnNode, Comments, PpAnn, PrintState, State, print_crate};
+pub use state::{print_crate, AnnNode, Comments, PpAnn, PrintState, State};
 
 pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
     State::new().nonterminal_to_string(nt)
@@ -63,6 +63,10 @@ pub fn path_segment_to_string(p: &ast::PathSegment) -> String {
     State::new().path_segment_to_string(p)
 }
 
+pub fn stmt_to_string(p: &ast::Stmt) -> String {
+    State::new().stmt_to_string(p)
+}
+
 pub fn vis_to_string(v: &ast::Visibility) -> String {
     State::new().vis_to_string(v)
 }

compiler/rustc_parse/src/parser/item.rs

@@ -10,18 +10,19 @@ use rustc_ast::util::case::Case;
 use rustc_ast::{self as ast};
 use rustc_ast_pretty::pprust;
 use rustc_errors::codes::*;
-use rustc_errors::{Applicability, PResult, StashKey, struct_span_code_err};
+use rustc_errors::{struct_span_code_err, Applicability, PResult, StashKey};
 use rustc_span::edit_distance::edit_distance;
 use rustc_span::edition::Edition;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
-use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, source_map};
-use thin_vec::{ThinVec, thin_vec};
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{source_map, ErrorGuaranteed, Span, DUMMY_SP};
+use thin_vec::{thin_vec, ThinVec};
 use tracing::debug;
 
-use super::diagnostics::{ConsumeClosingDelim, dummy_arg};
+use super::diagnostics::{dummy_arg, ConsumeClosingDelim};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{
-    AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, Trailing, UsePreAttrPos,
+    AttemptLocalParseRecovery, AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle,
+    Trailing, UsePreAttrPos,
 };
 use crate::errors::{self, MacroExpandsToAdtField};
 use crate::{fluent_generated as fluent, maybe_whole};
@@ -75,20 +76,8 @@ impl<'a> Parser<'a> {
         }
 
         if !self.eat(term) {
-            let token_str = super::token_descr(&self.token);
             if !self.maybe_consume_incorrect_semicolon(items.last().map(|x| &**x)) {
-                let msg = format!("expected item, found {token_str}");
-                let mut err = self.dcx().struct_span_err(self.token.span, msg);
-                let span = self.token.span;
-                if self.is_kw_followed_by_ident(kw::Let) {
-                    err.span_label(
-                        span,
-                        "consider using `const` or `static` instead of `let` for global variables",
-                    );
-                } else {
-                    err.span_label(span, "expected item")
-                        .note("for a full list of items that can appear in modules, see <https://doc.rust-lang.org/reference/items.html>");
-                };
+                let err = self.fallback_incorrect_item();
                 return Err(err);
             }
         }
@@ -97,6 +86,55 @@ impl<'a> Parser<'a> {
         let mod_spans = ModSpans { inner_span: lo.to(self.prev_token.span), inject_use_span };
         Ok((attrs, items, mod_spans))
     }
+
+    /// Tries to parse the item as a statement to provide further diagnostics.
+    fn fallback_incorrect_item(&mut self) -> rustc_errors::Diag<'a> {
+        let token_str = super::token_descr(&self.token);
+        let mut err = self
+            .dcx()
+            .struct_span_err(self.token.span, format!("expected item, found {token_str}"));
+
+        match self.parse_full_stmt(AttemptLocalParseRecovery::No) {
+            Ok(Some(stmt)) => {
+                let span = stmt.span;
+                match &stmt.kind {
+                    StmtKind::Let(_) => {
+                        err.span_label(span, "unexpected `let` binding outside of a function")
+                            .help(format!("consider using `const` or `static` instead of `let` for global variables, or put it inside of a function:  fn foo() {{ {} }}",
+                            pprust::stmt_to_string(&stmt)));
+                    }
+                    StmtKind::Semi(expr) => {
+                        err.span_label(span, "unexpected expression").help(format!(
+                            "consider putting it inside a function: fn foo() {{ {}; }}",
+                            pprust::expr_to_string(expr)
+                        ));
+                    }
+                    StmtKind::Expr(expr) => {
+                        err.span_label(span, "unexpected expression").help(format!(
+                            "consider putting it inside a function: fn foo() {{ {} }}",
+                            pprust::expr_to_string(expr)
+                        ));
+                    }
+                    StmtKind::Empty => {
+                        unreachable!(
+                            "Should have been handled by maybe_consume_incorrect_semicolon"
+                        );
+                    }
+                    StmtKind::Item(_) | StmtKind::MacCall(_) => {
+                        unreachable!("These should be valid.")
+                    }
+                };
+            }
+            Ok(None) => {} // It's not a statement, not much we can do.
+            Err(e) => {
+                // We don't really care about an error parsing this statement.
+                e.cancel();
+            }
+        }
+        err.note("for a full list of items that can appear in modules, see <https://doc.rust-lang.org/reference/items.html>");
+
+        err
+    }
 }
 
 pub(super) type ItemInfo = (Ident, ItemKind);
@@ -452,7 +490,11 @@ impl<'a> Parser<'a> {
             None
         };
 
-        if let Some(err) = err { Err(self.dcx().create_err(err)) } else { Ok(()) }
+        if let Some(err) = err {
+            Err(self.dcx().create_err(err))
+        } else {
+            Ok(())
+        }
     }
 
     fn parse_item_builtin(&mut self) -> PResult<'a, Option<ItemInfo>> {
@@ -1112,7 +1154,11 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
-        if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
+        if self.eat_keyword(kw::As) {
+            self.parse_ident_or_underscore().map(Some)
+        } else {
+            Ok(None)
+        }
     }
 
     fn parse_ident_or_underscore(&mut self) -> PResult<'a, Ident> {
@@ -1195,7 +1241,7 @@ impl<'a> Parser<'a> {
         mut safety: Safety,
     ) -> PResult<'a, ItemInfo> {
         let abi = self.parse_abi(); // ABI?
-        // FIXME: This recovery should be tested better.
+                                    // FIXME: This recovery should be tested better.
         if safety == Safety::Default
             && self.token.is_keyword(kw::Unsafe)
             && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace))
@@ -1897,10 +1943,10 @@ impl<'a> Parser<'a> {
                 // Try to recover extra trailing angle brackets
                 if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
                     if let Some(last_segment) = segments.last() {
-                        let guar = self.check_trailing_angle_brackets(last_segment, &[
-                            &token::Comma,
-                            &token::CloseDelim(Delimiter::Brace),
-                        ]);
+                        let guar = self.check_trailing_angle_brackets(
+                            last_segment,
+                            &[&token::Comma, &token::CloseDelim(Delimiter::Brace)],
+                        );
                         if let Some(_guar) = guar {
                             // Handle a case like `Vec<u8>>,` where we can continue parsing fields
                             // after the comma
@@ -2107,7 +2153,7 @@ impl<'a> Parser<'a> {
                 self.unexpected()?;
             }
             let body = self.parse_token_tree(); // `MacBody`
-            // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
+                                                // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
             let bspan = body.span();
             let arrow = TokenTree::token_alone(token::FatArrow, pspan.between(bspan)); // `=>`
             let tokens = TokenStream::new(vec![params, arrow, body]);