make the partial match suggestion easier to copy

Author: cometkim

jscomp/build_tests/super_errors/expected/warnings4.res.expected

@@ -10,4 +10,4 @@
   14 │ 
 
   You forgot to handle a possible case here, for example: 
-  #second(_) | #fourth | #third
+  | #second(_) | #fourth | #third

jscomp/build_tests/super_errors/expected/warnings5.res.expected

@@ -24,7 +24,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   15 │ switch y {
 
   You forgot to handle a possible case here, for example: 
-  {otherValue: true, _}
+  | {otherValue: true, _}
 
 
   Warning number 9
@@ -52,7 +52,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   19 │ let arr = [1]
 
   You forgot to handle a possible case here, for example: 
-  {typ: WithPayload(false), _}
+  | {typ: WithPayload(false), _}
 | {typ: Variant | One | Two | Three | Four | Five | Six | Seven(_), _}
 
 
@@ -68,7 +68,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   25 │ switch arr {
 
   You forgot to handle a possible case here, for example: 
-  [_]
+  | [_]
 
 
   Warning number 8
@@ -83,7 +83,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   29 │ switch arr {
 
   You forgot to handle a possible case here, for example: 
-  []
+  | []
 
 
   Warning number 8
@@ -98,7 +98,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   33 │ let lst = list{}
 
   You forgot to handle a possible case here, for example: 
-  [1, 0] | [0, _] | []
+  | [1, 0] | [0, _] | []
 
 
   Warning number 8
@@ -113,7 +113,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   39 │ switch lst {
 
   You forgot to handle a possible case here, for example: 
-  list{_, ..._}
+  | list{_, ..._}
 
 
   Warning number 8
@@ -128,7 +128,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   43 │ switch lst {
 
   You forgot to handle a possible case here, for example: 
-  list{1, 2, _, ..._} | list{1, 0, ..._} | list{1} | list{0, ..._} | list{}
+  | list{1, 2, _, ..._} | list{1, 0, ..._} | list{1} | list{0, ..._} | list{}
 
 
   Warning number 8
@@ -143,7 +143,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   47 │ switch "abc" {
 
   You forgot to handle a possible case here, for example: 
-  list{1, _, ..._} | list{0, ..._} | list{}
+  | list{1, _, ..._} | list{0, ..._} | list{}
 
 
   Warning number 8
@@ -158,7 +158,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   51 │ switch 0 {
 
   You forgot to handle a possible case here, for example: 
-  "*"
+  | "*"
 
 
   Warning number 8
@@ -173,7 +173,7 @@ Either bind these labels explicitly or add ', _' to the pattern.
   55 │ let tuple = (1, true)
 
   You forgot to handle a possible case here, for example: 
-  0
+  | 0
 
 
   Warning number 8
@@ -187,4 +187,4 @@ Either bind these labels explicitly or add ', _' to the pattern.
   60 │ 
 
   You forgot to handle a possible case here, for example: 
-  (_, true)
+  | (_, true)

jscomp/ml/parmatch.ml

@@ -2099,6 +2099,7 @@ let do_check_partial ?pred exhaust loc casel pss = match pss with
               let errmsg =
                 try
                   let buf = Buffer.create 16 in
+                  Buffer.add_string buf "| ";
                   Buffer.add_string buf (!print_res_pat v);
                   begin match check_partial_all v casel with
                   | None -> ()