Take care of some corner-cases of non-const tracking.

src/calendar.c

@@ -1761,6 +1761,8 @@ static void GenerateCalEntries(int col)
             tok.type != T_Else &&
             tok.type != T_EndIf &&
             tok.type != T_IfTrig &&
+            tok.type != T_Set &&
+            tok.type != T_Fset &&
             should_ignore_line())
         {
             /* DO NOTHING */

src/expr.c

@@ -747,6 +747,10 @@ eval_userfunc(expr_node *node, Value *locals, Value *ans, int *nonconst)
 
     FuncRecursionLevel++;
 
+    if (!f->is_constant) {
+        nonconst_debug(*nonconst, tr("User function `%s' defined in non-constant context makes expression non-constant"), f->name);
+        *nonconst = 1;
+    }
     /* Add a call to the call stack for better error messages */
     pushed = push_call(f->filename, f->name, f->lineno, f->lineno_start);
 

src/main.c

@@ -287,6 +287,8 @@ static void DoReminders(void)
             tok.type != T_Else &&
             tok.type != T_EndIf &&
             tok.type != T_IfTrig &&
+            tok.type != T_Set &&
+            tok.type != T_Fset &&
             should_ignore_line())
         {
             /*** IGNORE THE LINE ***/

src/types.h

@@ -296,6 +296,7 @@ typedef struct {
 typedef struct udf_struct {
     struct hash_link link;
     char name[VAR_NAME_LEN+1];
+    char is_constant;
     expr_node *node;
     char **args;
     int nargs;

src/userfns.c

@@ -196,6 +196,20 @@ int DoFset(ParsePtr p)
     /* Convert to lower-case */
     strtolower(DBufValue(&buf));
 
+    /* If we're ignoring the line, just update is_constant flag if needed */
+    if (should_ignore_line()) {
+        if (in_constant_context()) {
+            DBufFree(&buf);
+            return OK;
+        }
+        existing = FindUserFunc(DBufValue(&buf));
+        if (existing) {
+            nonconst_debug(!existing->is_constant, tr("Function definition considered non-constant because of context"));
+            existing->is_constant = 0;
+        }
+        DBufFree(&buf);
+        return OK;
+    }
     /* If the function exists and was defined at the same line of the same
        file, do nothing */
     existing = FindUserFunc(DBufValue(&buf));
@@ -240,6 +254,12 @@ int DoFset(ParsePtr p)
     func->lineno = LineNo;
     func->lineno_start = LineNoStart;
     func->recurse_flag = 0;
+    if (in_constant_context()) {
+        func->is_constant = 1;
+    } else {
+        nonconst_debug(0, tr("Function definition considered non-constant because of context"));
+        func->is_constant = 0;
+    }
     StrnCpy(func->name, DBufValue(&buf), VAR_NAME_LEN);
     DBufFree(&buf);
     if (!Hush) {

src/var.c

@@ -604,14 +604,31 @@ int DoSet (Parser *p)
     Value v;
     int r;
     int ch;
+    int ignoring = should_ignore_line();
     DynamicBuffer buf;
     DynamicBuffer buf2;
     DBufInit(&buf);
     DBufInit(&buf2);
+    Var *var;
 
     r = ParseIdentifier(p, &buf);
     if (r) return r;
 
+    if (ignoring) {
+        /* We're only here to mark a variable as non-const */
+        if (in_constant_context()) {
+            DBufFree(&buf);
+            return OK;
+        }
+        var = FindVar(DBufValue(&buf), 0);
+        if (var) {
+            nonconst_debug(var->nonconstant, tr("Variable assignment considered non-constant because of context"));
+            var->nonconstant = 1;
+        }
+        DBufFree(&buf);
+        return OK;
+    }
+
     /* Allow optional equals-sign:  SET var = value */
     ch = ParseNonSpaceChar(p, &r, 1);
     if (r) return r;

tests/test.cmp

@@ -24813,6 +24813,7 @@ TRANSLATE "Executing `%s' for INCLUDECMD and caching as `%s'" ""
 TRANSLATE "Found cached directory listing for `%s'" ""
 TRANSLATE "Function `%s' defined at %s(%s) should take %d argument%s, but actually takes %d" ""
 TRANSLATE "Function `%s' redefined: previously defined at %s(%s)" ""
+TRANSLATE "Function definition considered non-constant because of context" ""
 TRANSLATE "GetValidHebDate: Bad adarbehave value %d" ""
 TRANSLATE "Global variable `%s' makes expression non-constant" ""
 TRANSLATE "In" ""
@@ -24841,6 +24842,7 @@ TRANSLATE "System variable `$%s' makes expression non-constant" ""
 TRANSLATE "Undefined %s function: `%s'" ""
 TRANSLATE "Unmatched PUSH-OMIT-CONTEXT at %s(%d)" ""
 TRANSLATE "Unrecognized command; interpreting as REM" ""
+TRANSLATE "User function `%s' defined in non-constant context makes expression non-constant" ""
 TRANSLATE "Variable assignment considered non-constant because of context" ""
 TRANSLATE "Warning: Function name `%s...' truncated to `%s'" ""
 TRANSLATE "Warning: OMIT is ignored if you use OMITFUNC" ""

tests/test.rem

@@ -1532,6 +1532,32 @@ REM SCANFROM -7 MSG foo
 
 REM MSG [g(3)]
 
+# Check user-functions for constant-ness
+FUNSET f
+IF today() > '1990-01-01'
+    FSET f(x) 2
+ELSE
+    FSET f(x) 3
+ENDIF
+
+SET a f(1)
+
+FUNSET f
+FSET f(x) '1990-01-01'
+IF today() < '1990-01-01'
+    FSET f(x) '2025-12-31'
+ENDIF
+
+set a f(1)
+FUNSET F
+
+SET a 1
+IF today() < '1990-01-01'
+    SET a 2
+ENDIF
+
+dump -c a
+
 DEBUG -n
 
 DEBUG -e