patch 9.0.1558: wrong error for unreachable code after :throw

Problem:    Wrong error for unreachable code after :throw.
Solution:   Adjust the error message.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 03a6e2c..265f846 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -3485,7 +3485,7 @@
 	    }
 	}
 
-	if (cctx.ctx_had_return
+	if ((cctx.ctx_had_return || cctx.ctx_had_throw)
 		&& ea.cmdidx != CMD_elseif
 		&& ea.cmdidx != CMD_else
 		&& ea.cmdidx != CMD_endif
@@ -3496,9 +3496,11 @@
 		&& ea.cmdidx != CMD_endtry
 		&& !ignore_unreachable_code_for_testing)
 	{
-	    emsg(_(e_unreachable_code_after_return));
+	    semsg(_(e_unreachable_code_after_str),
+				     cctx.ctx_had_return ? "return" : "throw");
 	    goto erret;
 	}
+	cctx.ctx_had_throw = FALSE;
 
 	p = skipwhite(p);
 	if (ea.cmdidx != CMD_SIZE
@@ -3612,7 +3614,7 @@
 		    break;
 	    case CMD_throw:
 		    line = compile_throw(p, &cctx);
-		    cctx.ctx_had_return = TRUE;
+		    cctx.ctx_had_throw = TRUE;
 		    break;
 
 	    case CMD_eval:
@@ -3765,7 +3767,9 @@
 	goto erret;
     }
 
-    if (!cctx.ctx_had_return)
+    // TODO: if a function ends in "throw" but there was a return elsewhere we
+    // should not assume the return type is "void".
+    if (!cctx.ctx_had_return && !cctx.ctx_had_throw)
     {
 	if (ufunc->uf_ret_type->tt_type == VAR_UNKNOWN)
 	    ufunc->uf_ret_type = &t_void;