Suggest add missing , before doc comments in parsing item list

Signed-off-by: xizheyin <[email protected]>

Author: xizheyin

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -685,24 +685,38 @@ impl<'a> Parser<'a> {
             );
         }
 
+        // This is used to avoid adding suggestions for doc comments in item list.
+        let is_expect_item_list_comma =
+            edible.len() == 1 && edible.iter().any(|e| e.token_type == TokenType::Comma);
         if let token::DocComment(kind, style, _) = self.token.kind {
-            // We have something like `expr //!val` where the user likely meant `expr // !val`
-            let pos = self.token.span.lo() + BytePos(2);
-            let span = self.token.span.with_lo(pos).with_hi(pos);
-            err.span_suggestion_verbose(
-                span,
-                format!(
-                    "add a space before {} to write a regular comment",
-                    match (kind, style) {
-                        (token::CommentKind::Line, ast::AttrStyle::Inner) => "`!`",
-                        (token::CommentKind::Block, ast::AttrStyle::Inner) => "`!`",
-                        (token::CommentKind::Line, ast::AttrStyle::Outer) => "the last `/`",
-                        (token::CommentKind::Block, ast::AttrStyle::Outer) => "the last `*`",
-                    },
-                ),
-                " ".to_string(),
-                Applicability::MachineApplicable,
-            );
+            if !is_expect_item_list_comma {
+                // We have something like `expr //!val` where the user likely meant `expr // !val`
+                let pos = self.token.span.lo() + BytePos(2);
+                let span = self.token.span.with_lo(pos).with_hi(pos);
+                err.span_suggestion_verbose(
+                    span,
+                    format!(
+                        "add a space before {} to write a regular comment",
+                        match (kind, style) {
+                            (token::CommentKind::Line, ast::AttrStyle::Inner) => "`!`",
+                            (token::CommentKind::Block, ast::AttrStyle::Inner) => "`!`",
+                            (token::CommentKind::Line, ast::AttrStyle::Outer) => "the last `/`",
+                            (token::CommentKind::Block, ast::AttrStyle::Outer) => "the last `*`",
+                        },
+                    ),
+                    " ".to_string(),
+                    Applicability::MachineApplicable,
+                );
+            } else {
+                // For fine-grained suggestions, we should suggest to add a comma before the doc comment
+                // like `expr, //!val`
+                err.span_suggestion_verbose(
+                    self.prev_token.span.shrink_to_hi(),
+                    "missing `,` before the doc comment",
+                    ", ".to_string(),
+                    Applicability::MachineApplicable,
+                );
+            }
         }
 
         let sp = if self.token == token::Eof {

compiler/rustc_parse/src/parser/mod.rs

@@ -918,15 +918,27 @@ impl<'a> Parser<'a> {
                                 Ok(t) => {
                                     // Parsed successfully, therefore most probably the code only
                                     // misses a separator.
-                                    expect_err
-                                        .with_span_suggestion_short(
+
+                                    // FIXME(xizheyin): This is a hack to avoid adding suggestions for doc comments in item list.
+                                    let contains_missing_comma_suggestion =
+                                        expect_err.suggestions.clone().unwrap_tag().iter().any(
+                                            |s| {
+                                                if let Some(msg) = s.msg.as_str() {
+                                                    msg.contains("missing `,`")
+                                                } else {
+                                                    false
+                                                }
+                                            },
+                                        );
+                                    if !contains_missing_comma_suggestion {
+                                        expect_err.span_suggestion_short(
                                             sp,
                                             format!("missing `{token_str}`"),
                                             token_str,
                                             Applicability::MaybeIncorrect,
-                                        )
-                                        .emit();
-
+                                        );
+                                    }
+                                    expect_err.emit();
                                     v.push(t);
                                     continue;
                                 }

tests/ui/enum/enum-lack-comma-suggestion-issue-142311.stderr

@@ -6,13 +6,9 @@ LL |     Bar
 LL |     /// Like where people drink
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ unexpected token
    |
-help: add a space before the last `/` to write a regular comment
+help: missing `,` before the doc comment
    |
-LL |     // / Like where people drink
-   |       +
-help: missing `,`
-   |
-LL |     Bar,
+LL |     Bar, 
    |        +
 
 error: expected one of `(`, `,`, `=`, `{`, or `}`, found doc comment `///xxxxxx`
@@ -21,13 +17,9 @@ error: expected one of `(`, `,`, `=`, `{`, or `}`, found doc comment `///xxxxxx`
 LL |     Baa///xxxxxx
    |        ^^^^^^^^^ expected one of `(`, `,`, `=`, `{`, or `}`
    |
-help: add a space before the last `/` to write a regular comment
-   |
-LL |     Baa// /xxxxxx
-   |          +
-help: missing `,`
+help: missing `,` before the doc comment
    |
-LL |     Baa,///xxxxxx
+LL |     Baa, ///xxxxxx
    |        +
 
 error: expected one of `(`, `,`, `=`, `{`, or `}`, found doc comment `///xxxxxx`
@@ -38,10 +30,10 @@ LL |     Baz///xxxxxx
    |
    = help: doc comments must come before what they document, if a comment was intended use `//`
    = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
-help: add a space before the last `/` to write a regular comment
+help: missing `,` before the doc comment
    |
-LL |     Baz// /xxxxxx
-   |          +
+LL |     Baz, ///xxxxxx
+   |        +
 
 error: aborting due to 3 previous errors