patch 8.2.3689: ex_let_one() is too long

Problem:    ex_let_one() is too long.
Solution:   Split into multiple functions.

src/evalvars.c

@@ -1289,39 +1289,20 @@ list_arg_vars(exarg_T *eap, char_u *arg, int *first)
 }
 
 /*
- * Set one item of ":let var = expr" or ":let [v1, v2] = list" to its value.
+ * Set an environment variable, part of ex_let_one().
- * Returns a pointer to the char just after the var name.
- * Returns NULL if there is an error.
  */
     static char_u *
-ex_let_one(
+ex_let_env(
-    char_u	*arg,		// points to variable name
+    char_u	*arg,
-    typval_T	*tv,		// value to assign to variable
+    typval_T	*tv,
-    int		copy,		// copy value from "tv"
+    int		flags,
-    int		flags,		// ASSIGN_CONST, ASSIGN_FINAL, etc.
+    char_u	*endchars,
-    char_u	*endchars,	// valid chars after variable name  or NULL
+    char_u	*op)
-    char_u	*op,		// "+", "-", "."  or NULL
-    int		var_idx)	// variable index for "let [a, b] = list"
 {
-    int		c1;
-    char_u	*name;
-    char_u	*p;
     char_u	*arg_end = NULL;
+    char_u	*name;
     int		len;
-    int		opt_flags;
-    char_u	*tofree = NULL;
 
-    if (in_vim9script() && (flags & (ASSIGN_NO_DECL | ASSIGN_DECL)) == 0
-			&& (flags & (ASSIGN_CONST | ASSIGN_FINAL)) == 0
-				  && vim_strchr((char_u *)"$@&", *arg) != NULL)
-    {
-	vim9_declare_error(arg);
-	return NULL;
-    }
-
-    // ":let $VAR = expr": Set environment variable.
-    if (*arg == '$')
-    {
     if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
 					 && (flags & ASSIGN_FOR_LOOP) == 0)
     {
@@ -1344,7 +1325,10 @@ ex_let_one(
 	    emsg(_(e_unexpected_characters_in_let));
 	else if (!check_secure())
 	{
-		c1 = name[len];
+	    char_u	*tofree = NULL;
+	    int		c1 = name[len];
+	    char_u	*p;
+
 	    name[len] = NUL;
 	    p = tv_get_string_chk(tv);
 	    if (p != NULL && op != NULL && *op == '.')
@@ -1368,20 +1352,31 @@ ex_let_one(
 	    vim_free(tofree);
 	}
     }
-    }
+    return arg_end;
+}
+
+/*
+ * Set an option, part of ex_let_one().
+ */
+    static char_u *
+ex_let_option(
+    char_u	*arg,
+    typval_T	*tv,
+    int		flags,
+    char_u	*endchars,
+    char_u	*op)
+{
+    char_u	*p;
+    int		opt_flags;
+    char_u	*arg_end = NULL;
 
-    // ":let &option = expr": Set option value.
-    // ":let &l:option = expr": Set local option value.
-    // ":let &g:option = expr": Set global option value.
-    // ":for &ts in range(8)": Set option value for for loop
-    else if (*arg == '&')
-    {
     if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
 					 && (flags & ASSIGN_FOR_LOOP) == 0)
     {
 	emsg(_(e_const_option));
 	return NULL;
     }
+
     // Find the end of the name.
     p = find_option_end(&arg, &opt_flags);
     if (p == NULL || (endchars != NULL
@@ -1389,6 +1384,7 @@ ex_let_one(
 	emsg(_(e_unexpected_characters_in_let));
     else
     {
+	int	    c1;
 	long	    n = 0;
 	getoption_T opt_type;
 	long	    numval;
@@ -1422,8 +1418,7 @@ ex_let_one(
 
 	if (op != NULL && *op != '=')
 	{
-		if (((opt_type == gov_bool || opt_type == gov_number)
+	    if (((opt_type == gov_bool || opt_type == gov_number) && *op == '.')
-								 && *op == '.')
 		    || (opt_type == gov_string && *op != '.'))
 	    {
 		semsg(_(e_letwrong), op);
@@ -1472,11 +1467,22 @@ ex_let_one(
 	*p = c1;
 	vim_free(stringval);
     }
-    }
+    return arg_end;
+}
+
+/*
+ * Set a register, part of ex_let_one().
+ */
+    static char_u *
+ex_let_register(
+    char_u	*arg,
+    typval_T	*tv,
+    int		flags,
+    char_u	*endchars,
+    char_u	*op)
+{
+    char_u	*arg_end = NULL;
 
-    // ":let @r = expr": Set register contents.
-    else if (*arg == '@')
-    {
     if ((flags & (ASSIGN_CONST | ASSIGN_FINAL))
 					 && (flags & ASSIGN_FOR_LOOP) == 0)
     {
@@ -1492,12 +1498,14 @@ ex_let_one(
     else
     {
 	char_u	*ptofree = NULL;
-	    char_u	*s;
+	char_u	*p;
 
 	p = tv_get_string_chk(tv);
 	if (p != NULL && op != NULL && *op == '.')
 	{
-		s = get_reg_contents(*arg == '@' ? '"' : *arg, GREG_EXPR_SRC);
+	    char_u  *s = get_reg_contents(*arg == '@'
+						  ? '"' : *arg, GREG_EXPR_SRC);
+
 	    if (s != NULL)
 	    {
 		p = ptofree = concat_str(s, p);
@@ -1511,15 +1519,60 @@ ex_let_one(
 	}
 	vim_free(ptofree);
     }
+    return arg_end;
+}
+
+/*
+ * Set one item of ":let var = expr" or ":let [v1, v2] = list" to its value.
+ * Returns a pointer to the char just after the var name.
+ * Returns NULL if there is an error.
+ */
+    static char_u *
+ex_let_one(
+    char_u	*arg,		// points to variable name
+    typval_T	*tv,		// value to assign to variable
+    int		copy,		// copy value from "tv"
+    int		flags,		// ASSIGN_CONST, ASSIGN_FINAL, etc.
+    char_u	*endchars,	// valid chars after variable name  or NULL
+    char_u	*op,		// "+", "-", "."  or NULL
+    int		var_idx)	// variable index for "let [a, b] = list"
+{
+    char_u	*arg_end = NULL;
+
+    if (in_vim9script() && (flags & (ASSIGN_NO_DECL | ASSIGN_DECL)) == 0
+			&& (flags & (ASSIGN_CONST | ASSIGN_FINAL)) == 0
+				  && vim_strchr((char_u *)"$@&", *arg) != NULL)
+    {
+	vim9_declare_error(arg);
+	return NULL;
     }
 
+    if (*arg == '$')
+    {
+	// ":let $VAR = expr": Set environment variable.
+	return ex_let_env(arg, tv, flags, endchars, op);
+    }
+    else if (*arg == '&')
+    {
+	// ":let &option = expr": Set option value.
+	// ":let &l:option = expr": Set local option value.
+	// ":let &g:option = expr": Set global option value.
+	// ":for &ts in range(8)": Set option value for for loop
+	return ex_let_option(arg, tv, flags, endchars, op);
+    }
+    else if (*arg == '@')
+    {
+	// ":let @r = expr": Set register contents.
+	return ex_let_register(arg, tv, flags, endchars, op);
+    }
+    else if (eval_isnamec1(*arg) || *arg == '{')
+    {
+	lval_T	lv;
+	char_u	*p;
+
 	// ":let var = expr": Set internal variable.
 	// ":let var: type = expr": Set internal variable with type.
 	// ":let {expr} = expr": Idem, name made with curly braces
-    else if (eval_isnamec1(*arg) || *arg == '{')
-    {
-	lval_T	lv;
-
 	p = get_lval(arg, tv, &lv, FALSE, FALSE,
 		(flags & (ASSIGN_NO_DECL | ASSIGN_DECL))
 					   ? GLV_NO_DECL : 0, FNE_CHECK_START);
@@ -1527,7 +1580,9 @@ ex_let_one(
 	{
 	    if (endchars != NULL && vim_strchr(endchars,
 					   *skipwhite(lv.ll_name_end)) == NULL)
+	    {
 		emsg(_(e_unexpected_characters_in_let));
+	    }
 	    else
 	    {
 		set_var_lval(&lv, p, tv, copy, flags, op, var_idx);
@@ -1536,7 +1591,6 @@ ex_let_one(
 	}
 	clear_lval(&lv);
     }
-
     else
 	semsg(_(e_invarg2), arg);
 

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3689,
 /**/
     3688,
 /**/