patch 7.4.2119

Problem:    Closures are not supported.
Solution:   Capture variables in lambdas from the outer scope. (Yasuhiro
            Matsumoto, Ken Takata)

Author: brammool

runtime/doc/eval.txt

@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 7.4.  Last change: 2016 Jul 24
+*eval.txt*	For Vim version 7.4.  Last change: 2016 Jul 29
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -40,7 +40,7 @@ done, the features in this document are not available.	See |+eval| and
 There are nine types of variables:
 
 Number		A 32 or 64 bit signed number.  |expr-number| *Number*
-		64-bit Number is available only when compiled with the
+		64-bit Numbers are available only when compiled with the
 		|+num64| feature.
 		Examples:  -123  0x10  0177
 
@@ -1219,7 +1219,7 @@ the following ways:
 
 1. The body of the lambda expression is an |expr1| and not a sequence of |Ex|
    commands.
-2. The prefix "a:" is optional for arguments.  E.g.: >
+2. The prefix "a:" should not be used for arguments.  E.g.: >
 	:let F = {arg1, arg2 -> arg1 - arg2}
 	:echo F(5, 2)
 <	3
@@ -1228,6 +1228,18 @@ The arguments are optional.  Example: >
 	:let F = {-> 'error function'}
 	:echo F()
 <	error function
+							*closure*
+Lambda expressions can access outer scope variables and arguments.  This is
+often called a closure.  Example where "i" a and "a:arg" are used in a lambda
+while they exists in the function scope.  They remain valid even after the
+function returns: >
+	:function Foo(arg)
+	:  let i = 3
+	:  return {x -> x + i - a:arg}
+	:endfunction
+	:let Bar = Foo(4)
+	:echo Bar(6)
+<	5
 
 Examples for using a lambda expression with |sort()|, |map()| and |filter()|: >
 	:echo map([1, 2, 3], {idx, val -> val + 1})
@@ -1245,6 +1257,12 @@ The lambda expression is also useful for Channel, Job and timer: >
 
 Note how execute() is used to execute an Ex command.  That's ugly though.
 
+
+Lambda expressions have internal names like '<lambda>42'.  If you get an error
+for a lambda expression, you can find what it is with the following command: >
+	:function {'<lambda>42'}
+See also: |numbered-function|
+
 ==============================================================================
 3. Internal variable				*internal-variables* *E461*
 
@@ -7494,7 +7512,8 @@ test_null_string()					*test_null_string()*
 
 test_settime({expr})					*test_settime()*
 		Set the time Vim uses internally.  Currently only used for
-		timestamps in the history, as they are used in viminfo.
+		timestamps in the history, as they are used in viminfo, and
+		for undo.
 		{expr} must evaluate to a number.  When the value is zero the
 		normal behavior is restored.
 

src/eval.c

@@ -237,8 +237,8 @@ static int get_env_tv(char_u **arg, typval_T *rettv, int evaluate);
 
 static int get_env_len(char_u **arg);
 static char_u * make_expanded_name(char_u *in_start, char_u *expr_start, char_u *expr_end, char_u *in_end);
+static void check_vars(char_u *name, int len);
 static typval_T *alloc_string_tv(char_u *string);
-static hashtab_T *find_var_ht(char_u *name, char_u **varname);
 static void delete_var(hashtab_T *ht, hashitem_T *hi);
 static void list_one_var(dictitem_T *v, char_u *prefix, int *first);
 static void list_one_var_a(char_u *prefix, char_u *name, int type, char_u *string, int *first);
@@ -4332,6 +4332,9 @@ eval7(
 	    {
 		partial_T *partial;
 
+		if (!evaluate)
+		    check_vars(s, len);
+
 		/* If "s" is the name of a variable of type VAR_FUNC
 		 * use its contents. */
 		s = deref_func_name(s, &len, &partial, !evaluate);
@@ -4363,7 +4366,10 @@ eval7(
 	    else if (evaluate)
 		ret = get_var_tv(s, len, rettv, NULL, TRUE, FALSE);
 	    else
+	    {
+		check_vars(s, len);
 		ret = OK;
+	    }
 	}
 	vim_free(alias);
     }
@@ -5540,6 +5546,10 @@ set_ref_in_item(
 	    }
 	}
     }
+    else if (tv->v_type == VAR_FUNC)
+    {
+	abort = set_ref_in_func(tv->vval.v_string, copyID);
+    }
     else if (tv->v_type == VAR_PARTIAL)
     {
 	partial_T	*pt = tv->vval.v_partial;
@@ -5549,6 +5559,8 @@ set_ref_in_item(
 	 */
 	if (pt != NULL)
 	{
+	    abort = set_ref_in_func(pt->pt_name, copyID);
+
 	    if (pt->pt_dict != NULL)
 	    {
 		typval_T dtv;
@@ -6790,6 +6802,34 @@ get_var_tv(
     return ret;
 }
 
+/*
+ * Check if variable "name[len]" is a local variable or an argument.
+ * If so, "*eval_lavars_used" is set to TRUE.
+ */
+    static void
+check_vars(char_u *name, int len)
+{
+    int		cc;
+    char_u	*varname;
+    hashtab_T	*ht;
+
+    if (eval_lavars_used == NULL)
+	return;
+
+    /* truncate the name, so that we can use strcmp() */
+    cc = name[len];
+    name[len] = NUL;
+
+    ht = find_var_ht(name, &varname);
+    if (ht == get_funccal_local_ht() || ht == get_funccal_args_ht())
+    {
+	if (find_var(name, NULL, TRUE) != NULL)
+	    *eval_lavars_used = TRUE;
+    }
+
+    name[len] = cc;
+}
+
 /*
  * Handle expr[expr], expr[expr:expr] subscript and .name lookup.
  * Also handle function call with Funcref variable: func(expr)
@@ -7274,13 +7314,20 @@ find_var(char_u *name, hashtab_T **htp, int no_autoload)
 {
     char_u	*varname;
     hashtab_T	*ht;
+    dictitem_T	*ret = NULL;
 
     ht = find_var_ht(name, &varname);
     if (htp != NULL)
 	*htp = ht;
     if (ht == NULL)
 	return NULL;
-    return find_var_in_ht(ht, *name, varname, no_autoload || htp != NULL);
+    ret = find_var_in_ht(ht, *name, varname, no_autoload || htp != NULL);
+    if (ret != NULL)
+	return ret;
+
+    /* Search in parent scope for lambda */
+    return find_var_in_scoped_ht(name, varname ? &varname : NULL,
+		no_autoload || htp != NULL);
 }
 
 /*
@@ -7341,7 +7388,7 @@ find_var_in_ht(
  * Return NULL if the name is not valid.
  * Set "varname" to the start of name without ':'.
  */
-    static hashtab_T *
+    hashtab_T *
 find_var_ht(char_u *name, char_u **varname)
 {
     hashitem_T	*hi;
@@ -7617,6 +7664,10 @@ set_var(
     }
     v = find_var_in_ht(ht, 0, varname, TRUE);
 
+    /* Search in parent scope which is possible to reference from lambda */
+    if (v == NULL)
+	v = find_var_in_scoped_ht(name, varname ? &varname : NULL, TRUE);
+
     if ((tv->v_type == VAR_FUNC || tv->v_type == VAR_PARTIAL)
 				      && var_check_func_name(name, v == NULL))
 	return;

src/ex_cmds2.c

@@ -1265,8 +1265,16 @@ set_ref_in_timer(int copyID)
 
     for (timer = first_timer; timer != NULL; timer = timer->tr_next)
     {
-	tv.v_type = VAR_PARTIAL;
-	tv.vval.v_partial = timer->tr_partial;
+	if (timer->tr_partial != NULL)
+	{
+	    tv.v_type = VAR_PARTIAL;
+	    tv.vval.v_partial = timer->tr_partial;
+	}
+	else
+	{
+	    tv.v_type = VAR_FUNC;
+	    tv.vval.v_string = timer->tr_callback;
+	}
 	abort = abort || set_ref_in_item(&tv, copyID, NULL, NULL);
     }
     return abort;

src/globals.h

@@ -1658,6 +1658,9 @@ EXTERN time_T time_for_testing INIT(= 0);
 
 /* Abort conversion to string after a recursion error. */
 EXTERN int  did_echo_string_emsg INIT(= FALSE);
+
+/* Used for checking if local variables or arguments used in a lambda. */
+EXTERN int *eval_lavars_used INIT(= NULL);
 #endif
 
 /*

src/proto/eval.pro

@@ -87,6 +87,7 @@ char_u *get_tv_string_chk(typval_T *varp);
 char_u *get_tv_string_buf_chk(typval_T *varp, char_u *buf);
 dictitem_T *find_var(char_u *name, hashtab_T **htp, int no_autoload);
 dictitem_T *find_var_in_ht(hashtab_T *ht, int htname, char_u *varname, int no_autoload);
+hashtab_T *find_var_ht(char_u *name, char_u **varname);
 char_u *get_var_value(char_u *name);
 void new_script_vars(scid_T id);
 void init_var_dict(dict_T *dict, dictitem_T *dict_var, int scope);

src/proto/userfunc.pro

@@ -46,7 +46,9 @@ void *clear_current_funccal(void);
 void restore_current_funccal(void *f);
 void list_func_vars(int *first);
 dict_T *get_current_funccal_dict(hashtab_T *ht);
+dictitem_T *find_var_in_scoped_ht(char_u *name, char_u **varname, int no_autoload);
 int set_ref_in_previous_funccal(int copyID);
 int set_ref_in_call_stack(int copyID);
 int set_ref_in_func_args(int copyID);
+int set_ref_in_func(char_u *name, int copyID);
 /* vim: set ft=c : */