Defining function based on alias

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

It's pretty much always an error to define a function when the name of
the function is being expanded as an alias, right?  So we could make it
an error, possible with an option though this would need to be active by
default to make it useful.

% foo() { echo this is function foo; }
% alias foo='echo bar'
% foo() { echo this is not function foo; }
zsh: defining function based on alias `foo'
zsh: parse error near `()'

pws

diff --git a/Src/input.c b/Src/input.c
index eb968ea..f2c22c8 100644
--- a/Src/input.c
+++ b/Src/input.c
@@ -670,3 +670,22 @@ ingetptr(void)
 {
     return inbufptr;
 }
+
+/**/
+char *input_hasalias(void)
+{
+    int flags = inbufflags;
+    struct instacks *instackptr = instacktop;
+
+    for (;;)
+    {
+	if (!(flags & INP_CONT))
+	    break;
+	instackptr--;
+	if (instackptr->alias)
+	    return instackptr->alias->node.nam;
+	flags = instackptr->flags;
+    }
+
+    return NULL;
+}
diff --git a/Src/parse.c b/Src/parse.c
index 50a0d5f..1fed020 100644
--- a/Src/parse.c
+++ b/Src/parse.c
@@ -1738,6 +1738,7 @@ par_simple(int *cmplx, int nr)
 {
     int oecused = ecused, isnull = 1, r, argc = 0, p, isfunc = 0, sr = 0;
     int c = *cmplx, nrediradd, assignments = 0, ppost = 0, is_typeset = 0;
+    char *hasalias = input_hasalias();
     wordcode postassigns = 0;
 
     r = ecused;
@@ -1809,6 +1810,8 @@ par_simple(int *cmplx, int nr)
 	} else
 	    break;
 	zshlex();
+	if (!hasalias)
+	    hasalias = input_hasalias();
     }
     if (tok == AMPER || tok == AMPERBANG)
 	YYERROR(oecused);
@@ -1839,6 +1842,8 @@ par_simple(int *cmplx, int nr)
 			char *idstring = dupstrpfx(tokstr+1, eptr-tokstr-1);
 			redir_var = 1;
 			zshlex();
+			if (!hasalias)
+			    hasalias = input_hasalias();
 
 			if (IS_REDIROP(tok) && tokfd == -1)
 			{
@@ -1874,6 +1879,8 @@ par_simple(int *cmplx, int nr)
 		    argc++;
 		}
 		zshlex();
+		if (!hasalias)
+		    hasalias = input_hasalias();
 	    }
 	} else if (IS_REDIROP(tok)) {
 	    *cmplx = c = 1;
@@ -1902,6 +1909,8 @@ par_simple(int *cmplx, int nr)
 	    ecstr(name);
 	    ecstr(str);
 	    zshlex();
+	    if (!hasalias)
+		hasalias = input_hasalias();
 	} else if (tok == ENVARRAY) {
 	    int n, parr;
 
@@ -1936,6 +1945,10 @@ par_simple(int *cmplx, int nr)
 	    /* Error if preceding assignments */
 	    if (assignments || postassigns)
 		YYERROR(oecused);
+	    if (hasalias && argc) {
+		zwarn("defining function based on alias `%s'", hasalias);
+		YYERROR(oecused);
+	    }
 
 	    *cmplx = c;
 	    lineno = 0;