special-operator-p: don't report error entries as t.

* eval.c (special_operator_p): Do not return t for certain
symbols that are wired to error-throwing functions in the
table, whose purpose it is to detect certain unexpanded
syntax that is handled internally by the expander.

* txr.1: Documentation udpated in several places to clarify
that certain operators are not special operators.
Also expander-let is reclassified from Macro to Ooerator.

2 files changed, 46 insertions, 2 deletions

diff --git a/eval.c b/eval.c
index aaac3513..517e7ff6 100644
--- a/eval.c
+++ b/eval.c
@@ -6300,7 +6300,21 @@ val mboundp(val sym)
 
 val special_operator_p(val sym)
 {
-  return if2(gethash(op_table, sym), t);
+  val fun = gethash(op_table, sym);
+
+  if (fun) {
+    opfun_t fp = coerce(opfun_t, cptr_get(fun));
+
+    if (fp == op_error || fp == op_meta_error ||
+        fp == op_qquote_error || fp == op_unquote_error)
+    {
+      return nil;
+    }
+
+    return t;
+  }
+
+  return nil;
 }
 
 static val makunbound(val sym)
diff --git a/txr.1 b/txr.1
index 22b65d6b..016861a1 100644
--- a/txr.1
+++ b/txr.1
@@ -20497,6 +20497,21 @@ if
 is a symbol which names a special operator, otherwise it returns
 .codn nil .
 
+Certain operator symbols are not understood as special operators,
+and not reported as such by this function.
+
+The operators
+.codn macrolet ,
+.code symacrolet
+and
+.code expander-let
+are completely consumed by the macro expander, and do not appear
+in its output. Therefore they are never seen by evaluation or compilation
+and are not special operators for that reason.
+
+The unquoting and splicing operators in quasiquote syntax also aren't special
+operators. They are a notation recognized by the quasiquoting macro.
+
 .coNP Symbol Macro @ %fun%
 .desc
 The symbol macro
@@ -42436,6 +42451,11 @@ When another macro is tried, the process repeats, resulting in a search which
 proceeds as far as possible through outer lexical scopes and finally the
 global scope.
 
+The
+.code symacrolet
+symbol isn't a special operator, and is not reported as such by
+.codn special-operator-p .
+
 .coNP Function @ macro-form-p
 .synb
 .mets (macro-form-p < obj <> [ env ])
@@ -43324,6 +43344,11 @@ applies inside a
 form. Lexical operator macros do not shadow
 symbol macros under any circumstances.
 
+The
+.code symacrolet
+symbol isn't a special operator, and is not reported as such by
+.codn special-operator-p .
+
 .coNP Macros @ placelet and @ placelet*
 .synb
 .mets (placelet >> ({( sym << place )}*) << body-form *)
@@ -43465,7 +43490,7 @@ emanating from the
 .code delta
 form.
 
-.coNP Macro @ expander-let
+.coNP Operator @ expander-let
 .synb
 .mets (expander-let >> ({( sym << init-form )}*) << body-form *)
 .syne
@@ -43519,6 +43544,11 @@ A macro may generate an
 .code expander-let
 form in order to communicate values to macros contained in that form.
 
+The
+.code expander-let
+symbol isn't a special operator, and is not reported as such by
+.codn special-operator-p .
+
 .coNP Macro @ macro-time
 .synb
 .mets (macro-time << form *)