Do not suggest using | in let assignments

src/libsyntax/parse/parser.rs

@@ -3257,7 +3257,7 @@ impl<'a> Parser<'a> {
                           mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
 
-        let pat = self.parse_top_level_pat()?;
+        let pat = self.parse_top_level_pat(false)?;
         if !self.eat_keyword(kw::In) {
             let in_span = self.prev_span.between(self.span);
             let mut err = self.sess.span_diagnostic
@@ -3509,7 +3509,7 @@ impl<'a> Parser<'a> {
 
         let mut pats = Vec::new();
         loop {
-            pats.push(self.parse_top_level_pat()?);
+            pats.push(self.parse_top_level_pat(true)?);
 
             if self.token == token::OrOr {
                 let mut err = self.struct_span_err(self.span,
@@ -3860,7 +3860,7 @@ impl<'a> Parser<'a> {
     /// A wrapper around `parse_pat` with some special error handling for the
     /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
     /// to subpatterns within such).
-    fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
+    fn parse_top_level_pat(&mut self, is_match_arg: bool) -> PResult<'a, P<Pat>> {
         let pat = self.parse_pat(None)?;
         if self.token == token::Comma {
             // An unexpected comma after a top-level pattern is a clue that the
@@ -3877,20 +3877,29 @@ impl<'a> Parser<'a> {
                 err.cancel();
             }
             let seq_span = pat.span.to(self.prev_span);
-            let mut err = self.struct_span_err(comma_span,
-                                               "unexpected `,` in pattern");
+            let mut err = self.struct_span_err(
+                comma_span,
+                "unexpected `,` in pattern",
+            );
             if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
                 err.span_suggestion(
                     seq_span,
-                    "try adding parentheses to match on a tuple..",
+                    &format!("try adding parentheses to match on a tuple{}", if is_match_arg {
+                        "..."
+                    } else {
+                        ""
+                    }),
                     format!("({})", seq_snippet),
                     Applicability::MachineApplicable
-                ).span_suggestion(
-                    seq_span,
-                    "..or a vertical bar to match on multiple alternatives",
-                    format!("{}", seq_snippet.replace(",", " |")),
-                    Applicability::MachineApplicable
                 );
+                if is_match_arg {
+                    err.span_suggestion(
+                        seq_span,
+                        "...or a vertical bar to match on multiple alternatives",
+                        format!("{}", seq_snippet.replace(",", " |")),
+                        Applicability::MachineApplicable
+                    );
+                }
             }
             return Err(err);
         }
@@ -4149,7 +4158,7 @@ impl<'a> Parser<'a> {
     /// Parses a local variable declaration.
     fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
         let lo = self.prev_span;
-        let pat = self.parse_top_level_pat()?;
+        let pat = self.parse_top_level_pat(false)?;
 
         let (err, ty) = if self.eat(&token::Colon) {
             // Save the state of the parser before parsing type normally, in case there is a `:`

src/test/ui/did_you_mean/issue-48492-tuple-destructure-missing-parens.stderr

@@ -3,11 +3,11 @@ error: unexpected `,` in pattern
    |
 LL |     while let b1, b2, b3 = reading_frame.next().expect("there should be a start codon") {
    |                 ^
-help: try adding parentheses to match on a tuple..
+help: try adding parentheses to match on a tuple...
    |
 LL |     while let (b1, b2, b3) = reading_frame.next().expect("there should be a start codon") {
    |               ^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
+help: ...or a vertical bar to match on multiple alternatives
    |
 LL |     while let b1 | b2 | b3 = reading_frame.next().expect("there should be a start codon") {
    |               ^^^^^^^^^^^^
@@ -17,11 +17,11 @@ error: unexpected `,` in pattern
    |
 LL |     if let b1, b2, b3 = reading_frame.next().unwrap() {
    |              ^
-help: try adding parentheses to match on a tuple..
+help: try adding parentheses to match on a tuple...
    |
 LL |     if let (b1, b2, b3) = reading_frame.next().unwrap() {
    |            ^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
+help: ...or a vertical bar to match on multiple alternatives
    |
 LL |     if let b1 | b2 | b3 = reading_frame.next().unwrap() {
    |            ^^^^^^^^^^^^
@@ -31,11 +31,11 @@ error: unexpected `,` in pattern
    |
 LL |         Nucleotide::Adenine, Nucleotide::Cytosine, _ => true
    |                            ^
-help: try adding parentheses to match on a tuple..
+help: try adding parentheses to match on a tuple...
    |
 LL |         (Nucleotide::Adenine, Nucleotide::Cytosine, _) => true
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
+help: ...or a vertical bar to match on multiple alternatives
    |
 LL |         Nucleotide::Adenine | Nucleotide::Cytosine | _ => true
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -44,43 +44,19 @@ error: unexpected `,` in pattern
   --> $DIR/issue-48492-tuple-destructure-missing-parens.rs:67:10
    |
 LL |     for x, _barr_body in women.iter().map(|woman| woman.allosomes.clone()) {
-   |          ^
-help: try adding parentheses to match on a tuple..
-   |
-LL |     for (x, _barr_body) in women.iter().map(|woman| woman.allosomes.clone()) {
-   |         ^^^^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
-   |
-LL |     for x | _barr_body in women.iter().map(|woman| woman.allosomes.clone()) {
-   |         ^^^^^^^^^^^^^^
+   |         -^----------- help: try adding parentheses to match on a tuple: `(x, _barr_body)`
 
 error: unexpected `,` in pattern
   --> $DIR/issue-48492-tuple-destructure-missing-parens.rs:75:10
    |
 LL |     for x, y @ Allosome::Y(_) in men.iter().map(|man| man.allosomes.clone()) {
-   |          ^
-help: try adding parentheses to match on a tuple..
-   |
-LL |     for (x, y @ Allosome::Y(_)) in men.iter().map(|man| man.allosomes.clone()) {
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
-   |
-LL |     for x | y @ Allosome::Y(_) in men.iter().map(|man| man.allosomes.clone()) {
-   |         ^^^^^^^^^^^^^^^^^^^^^^
+   |         -^------------------- help: try adding parentheses to match on a tuple: `(x, y @ Allosome::Y(_))`
 
 error: unexpected `,` in pattern
   --> $DIR/issue-48492-tuple-destructure-missing-parens.rs:84:14
    |
 LL |     let women, men: (Vec<Genome>, Vec<Genome>) = genomes.iter().cloned()
-   |              ^
-help: try adding parentheses to match on a tuple..
-   |
-LL |     let (women, men): (Vec<Genome>, Vec<Genome>) = genomes.iter().cloned()
-   |         ^^^^^^^^^^^^
-help: ..or a vertical bar to match on multiple alternatives
-   |
-LL |     let women | men: (Vec<Genome>, Vec<Genome>) = genomes.iter().cloned()
-   |         ^^^^^^^^^^^
+   |         -----^---- help: try adding parentheses to match on a tuple: `(women, men)`
 
 error: aborting due to 6 previous errors
 

src/test/ui/suggestions/issue-61573.rs

@@ -0,0 +1,5 @@
+fn main() {
+    let a, b = x;
+    //~^ ERROR unexpected `,` in pattern
+    //~| HELP try adding parentheses to match on a tuple
+}

src/test/ui/suggestions/issue-61573.stderr

@@ -0,0 +1,8 @@
+error: unexpected `,` in pattern
+  --> $DIR/issue-61573.rs:2:10
+   |
+LL |     let a, b = x;
+   |         -^-- help: try adding parentheses to match on a tuple: `(a, b)`
+
+error: aborting due to previous error
+