patch 8.2.4971: Vim9: interpolated string seen as range

Problem:    Vim9: interpolated string seen as range.
Solution:   Recognize an interpolated string at the start of a command line.
            (closes #10434)

src/ex_docmd.c

@@ -3551,7 +3551,8 @@ find_ex_command(
 	    char_u  *swp;
 
 	    if (*eap->cmd == '&'
-		    || *eap->cmd == '$'
+		    || (eap->cmd[0] == '$'
+				  && eap->cmd[1] != '\'' && eap->cmd[1] != '"')
 		    || (eap->cmd[0] == '@'
 					&& (valid_yank_reg(eap->cmd[1], FALSE)
 						       || eap->cmd[1] == '@')))
@@ -3590,9 +3591,13 @@ find_ex_command(
 			    // "'string'->func()" is an expression.
 			 || *eap->cmd == '\''
 			    // '"string"->func()' is an expression.
-			 || (eap->cmd[0] == '0' && eap->cmd[1] == 'z')
-			    // '"string"->func()' is an expression.
 			 || *eap->cmd == '"'
+			    // '$"string"->func()' is an expression.
+			    // "$'string'->func()" is an expression.
+			 || (eap->cmd[0] == '$'
+			     && (eap->cmd[1] == '\'' || eap->cmd[1] == '"'))
+			    // '0z1234->func()' is an expression.
+			 || (eap->cmd[0] == '0' && eap->cmd[1] == 'z')
 			    // "g:varname" is an expression.
 			 || eap->cmd[1] == ':'
 			    )

src/testdir/test_vim9_expr.vim

@@ -3572,7 +3572,9 @@ def Test_expr8_method_call()
       setline(1, ['first', 'last'])
       'second'->append(1)
       "third"->append(2)
-      assert_equal(['first', 'second', 'third', 'last'], getline(1, '$'))
+      $"fourth"->append(3)
+      $'fifth'->append(4)
+      assert_equal(['first', 'second', 'third', 'fourth', 'fifth', 'last'], getline(1, '$'))
       bwipe!
 
       var bufnr = bufnr()

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4971,
 /**/
     4970,
 /**/