patch 9.0.1558: wrong error for unreachable code after :throw

Problem:    Wrong error for unreachable code after :throw.
Solution:   Adjust the error message.

src/errors.h

@@ -2809,8 +2809,8 @@ EXTERN char e_expected_nr_items_but_got_nr[]
 	INIT(= N_("E1093: Expected %d items but got %d"));
 EXTERN char e_import_can_only_be_used_in_script[]
 	INIT(= N_("E1094: Import can only be used in a script"));
-EXTERN char e_unreachable_code_after_return[]
+EXTERN char e_unreachable_code_after_str[]
-	INIT(= N_("E1095: Unreachable code after :return"));
+	INIT(= N_("E1095: Unreachable code after :%s"));
 EXTERN char e_returning_value_in_function_without_return_type[]
 	INIT(= N_("E1096: Returning a value in a function without a return type"));
 EXTERN char e_line_incomplete[]

src/testdir/test_vim9_script.vim

@@ -812,6 +812,30 @@ def Test_try_catch_throw()
   v9.CheckDefAndScriptSuccess(lines)
 enddef
 
+def Test_unreachable_after()
+  var lines =<< trim END
+      try
+        throw 'Error'
+        echo 'not reached'
+      catch /Error/
+      endtry
+  END
+  v9.CheckDefFailure(lines, 'E1095: Unreachable code after :throw')
+
+  lines =<< trim END
+      def SomeFunc(): number
+        try
+          return 3
+          echo 'not reached'
+        catch /Error/
+        endtry
+        return 4
+      enddef
+      defcompile
+  END
+  v9.CheckScriptFailure(lines, 'E1095: Unreachable code after :return')
+enddef
+
 def Test_throw_in_nested_try()
   var lines =<< trim END
       vim9script
@@ -1079,6 +1103,8 @@ def Test_nocatch_throw_silenced()
   source XthrowSilenced
 enddef
 
+" g:DeletedFunc() is found when compiling Test_try_catch_throw() and then
+" deleted, this should give a runtime error.
 def DeletedFunc(): list<any>
   return ['delete me']
 enddef

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1558,
 /**/
     1557,
 /**/

src/vim9.h

@@ -842,6 +842,7 @@ struct cctx_S {
     skip_T	ctx_skip;
     scope_T	*ctx_scope;	    // current scope, NULL at toplevel
     int		ctx_had_return;	    // last seen statement was "return"
+    int		ctx_had_throw;	    // last seen statement was "throw"
 
     cctx_T	*ctx_outer;	    // outer scope for lambda or nested
 				    // function

src/vim9compile.c

@@ -3485,7 +3485,7 @@ compile_def_function(
 	    }
 	}
 
-	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 @@ compile_def_function(
 		&& 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 @@ compile_def_function(
 		    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 @@ nextline:
 	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;