patch 8.2.1349: Vim9: can define a function with the name of an import

Problem:    Vim9: can define a function with the name of an import.
Solution:   Disallow using an existing name. (closes #6585)

src/globals.h

@@ -1746,6 +1746,7 @@ EXTERN char e_missing_dict_colon[] INIT(= N_("E720: Missing colon in Dictionary:
 EXTERN char e_duplicate_key[]	INIT(= N_("E721: Duplicate key in Dictionary: \"%s\""));
 EXTERN char e_missing_dict_comma[] INIT(= N_("E722: Missing comma in Dictionary: %s"));
 EXTERN char e_missing_dict_end[]    INIT(= N_("E723: Missing end of Dictionary '}': %s"));
+EXTERN char e_already_defined[] INIT(= N_("E1073: name already defined: %s"));
 #endif
 #ifdef FEAT_CLIENTSERVER
 EXTERN char e_invexprmsg[]	INIT(= N_("E449: Invalid expression received"));

src/testdir/test_vim9_script.vim

@@ -1618,6 +1618,39 @@ def Test_import_compile_error()
   delete('Ximport.vim')
 enddef
 
+def Test_func_overrules_import_fails()
+  let export_lines =<< trim END
+      vim9script
+      export def Func()
+        echo 'imported'
+      enddef
+  END
+  writefile(export_lines, 'XexportedFunc.vim')
+
+  let lines =<< trim END
+    vim9script
+    import Func from './XexportedFunc.vim'
+    def Func()
+      echo 'local to function'
+    enddef
+  END
+  CheckScriptFailure(lines, 'E1073:')
+
+  lines =<< trim END
+    vim9script
+    import Func from './XexportedFunc.vim'
+    def Outer()
+      def Func()
+        echo 'local to function'
+      enddef
+    enddef
+    defcompile
+  END
+  CheckScriptFailure(lines, 'E1073:')
+
+  delete('XexportedFunc.vim')
+enddef
+
 def Test_fixed_size_list()
   # will be allocated as one piece of memory, check that changes work
   let l = [1, 2, 3, 4]

src/userfunc.c

@@ -2652,6 +2652,7 @@ def_function(exarg_T *eap, char_u *name_arg)
     char_u	*skip_until = NULL;
     char_u	*heredoc_trimmed = NULL;
     int		vim9script = in_vim9script();
+    imported_T	*import = NULL;
 
     /*
      * ":function" without argument: list functions.
@@ -3235,17 +3236,29 @@ def_function(exarg_T *eap, char_u *name_arg)
 	}
 
 	fp = find_func_even_dead(name, is_global, NULL);
-	if (fp != NULL)
+	if (vim9script)
 	{
-	    int dead = fp->uf_flags & FC_DEAD;
+	    char_u *uname = untrans_function_name(name);
+
+	    import = find_imported(uname == NULL ? name : uname, 0, NULL);
+	}
+
+	if (fp != NULL || import != NULL)
+	{
+	    int dead = fp != NULL && (fp->uf_flags & FC_DEAD);
 
 	    // Function can be replaced with "function!" and when sourcing the
 	    // same script again, but only once.
-	    if (!dead && !eap->forceit
+	    // A name that is used by an import can not be overruled.
+	    if (import != NULL
+		    || (!dead && !eap->forceit
 			&& (fp->uf_script_ctx.sc_sid != current_sctx.sc_sid
-			    || fp->uf_script_ctx.sc_seq == current_sctx.sc_seq))
+			  || fp->uf_script_ctx.sc_seq == current_sctx.sc_seq)))
 	    {
-		emsg_funcname(e_funcexts, name);
+		if (vim9script)
+		    emsg_funcname(e_already_defined, name);
+		else
+		    emsg_funcname(e_funcexts, name);
 		goto erret;
 	    }
 	    if (fp->uf_calls > 0)

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1349,
 /**/
     1348,
 /**/

src/vim9compile.c

@@ -294,9 +294,10 @@ check_defined(char_u *p, size_t len, cctx_T *cctx)
     if (lookup_script(p, len) == OK
 	    || (cctx != NULL
 		&& (lookup_local(p, len, cctx) != NULL
-		    || find_imported(p, len, cctx) != NULL)))
+		    || lookup_arg(p, len, NULL, NULL, NULL, cctx) == OK))
+	    || find_imported(p, len, cctx) != NULL)
     {
-	semsg("E1073: imported name already defined: %s", p);
+	semsg(_(e_already_defined), p);
 	return FAIL;
     }
     return OK;
@@ -4899,17 +4900,21 @@ compile_nested_function(exarg_T *eap, cctx_T *cctx)
     int		is_global = *eap->arg == 'g' && eap->arg[1] == ':';
     char_u	*name_start = eap->arg;
     char_u	*name_end = to_name_end(eap->arg, is_global);
-    char_u	*name = get_lambda_name();
+    char_u	*lambda_name;
     lvar_T	*lvar;
     ufunc_T	*ufunc;
     int		r;
 
+    if (check_defined(name_start, name_end - name_start, cctx) == FAIL)
+	return NULL;
+
     eap->arg = name_end;
     eap->getline = exarg_getline;
     eap->cookie = cctx;
     eap->skip = cctx->ctx_skip == SKIP_YES;
     eap->forceit = FALSE;
-    ufunc = def_function(eap, name);
+    lambda_name = get_lambda_name();
+    ufunc = def_function(eap, lambda_name);
 
     if (ufunc == NULL)
 	return NULL;
@@ -4925,13 +4930,15 @@ compile_nested_function(exarg_T *eap, cctx_T *cctx)
 	if (func_name == NULL)
 	    r = FAIL;
 	else
-	    r = generate_NEWFUNC(cctx, name, func_name);
+	    r = generate_NEWFUNC(cctx, lambda_name, func_name);
     }
     else
     {
 	// Define a local variable for the function reference.
 	lvar = reserve_local(cctx, name_start, name_end - name_start,
 						    TRUE, ufunc->uf_func_type);
+	if (lvar == NULL)
+	    return NULL;
 	if (generate_FUNCREF(cctx, ufunc->uf_dfunc_idx) == FAIL)
 	    return NULL;
 	r = generate_STORE(cctx, ISN_STORE, lvar->lv_idx, NULL);