vim-patch:8.1.2262: unpack assignment in function not recognized

Problem:    Unpack assignment in function not recognized.
Solution:   Skip over "[a, b]". (closes vim/vim#5051)
1e673b9eb6

src/nvim/eval.c

@@ -21742,24 +21742,33 @@ void ex_function(exarg_T *eap)
       }
 
       // Check for ":let v =<< [trim] EOF"
+      //       and ":let [a, b] =<< [trim] EOF"
       arg = skipwhite(skiptowhite(p));
+      if (*arg == '[') {
+        arg = vim_strchr(arg, ']');
+      }
+      if (arg != NULL) {
         arg = skipwhite(skiptowhite(arg));
-      if (arg[0] == '=' && arg[1] == '<' && arg[2] =='<'
+        if (arg[0] == '='
-          && ((p[0] == 'l' && p[1] == 'e'
+            && arg[1] == '<'
+            && arg[2] =='<'
+            && (p[0] == 'l'
+                && p[1] == 'e'
                 && (!ASCII_ISALNUM(p[2])
-                   || (p[2] == 't' && !ASCII_ISALNUM(p[3])))))) {
+                    || (p[2] == 't' && !ASCII_ISALNUM(p[3]))))) {
           p = skipwhite(arg + 3);
           if (STRNCMP(p, "trim", 4) == 0) {
             // Ignore leading white space.
             p = skipwhite(p + 4);
-          heredoc_trimmed = vim_strnsave(theline,
+            heredoc_trimmed =
-                                         (int)(skipwhite(theline) - theline));
+              vim_strnsave(theline, (int)(skipwhite(theline) - theline));
           }
           skip_until = vim_strnsave(p, (int)(skiptowhite(p) - p));
           do_concat = false;
           is_heredoc = true;
         }
       }
+    }
 
     /* Add the line to the function. */
     ga_grow(&newlines, 1 + sourcing_lnum_off);

src/nvim/testdir/test_let.vim

@@ -289,4 +289,12 @@ E
      END
   endif
   call assert_equal([], check)
+
+  " unpack assignment
+  let [a, b, c] =<< END
+     x
+     \y
+     z
+END
+  call assert_equal(['     x', '     \y', '     z'], [a, b, c])
 endfunc