allow No to start identifier, but disallow all-No identifiers

Author: stevengj

NEWS.md

@@ -641,7 +641,7 @@ Language changes
 
   * Identifiers can now start with numeric symbols in category
     [No: Number, other](http://www.fileformat.info/info/unicode/category/No/list.htm),
-    allowing you to have variables with names like `⅓` or `¹x₂` ([#20278]).
+    allowing you to have variables with names like `⅓x` or `¹x₂` ([#20278]).
 
   * `@.` is now parsed as `@__dot__`, and can be used to add dots to
     every function call, operator, and assignment in an expression ([#20321]).

src/flisp/julia_extensions.c

@@ -269,10 +269,11 @@ value_t fl_accum_julia_symbol(fl_context_t *fl_ctx, value_t *args, uint32_t narg
         type_error(fl_ctx, "accum-julia-symbol", "wchar", args[0]);
     uint32_t wc = *(uint32_t*)cp_data((cprim_t*)ptr(args[0]));
     ios_t str;
-    int allascii=1;
+    int allascii=1, allNo=1;
     ios_mem(&str, 0);
     do {
         allascii &= (wc <= 0x7f);
+        allNo = allNo && UTF8PROC_CATEGORY_NO == utf8proc_category((utf8proc_int32_t) wc);
         ios_getutf8(s, &wc);
         if (wc == '!') {
             uint32_t nwc;
@@ -288,6 +289,8 @@ value_t fl_accum_julia_symbol(fl_context_t *fl_ctx, value_t *args, uint32_t narg
             break;
     } while (jl_id_char(wc));
     ios_pututf8(&str, 0);
+    if (allNo) /* identifiers cannot consist only of category-No */
+        lerrorf(fl_ctx, symbol(fl_ctx, "error"), "invalid identifier %s", str.buf);
     return symbol(fl_ctx, allascii ? str.buf : normalize(fl_ctx, str.buf));
 }
 

test/parse.jl

@@ -1078,8 +1078,8 @@ short_where_call = :(f(x::T) where T = T)
 @test short_where_call.args[2].head == :block
 
 # identifiers starting with category No:
-let ⅟₉₉ = 1/99, ¹x = 12
-    @test ⅟₉₉ == 1/99
+let ⅟₉₉x = 1/99, ¹x = 12
+    @test ⅟₉₉x == 1/99
     @test ¹x == 12
 end
 # `where` with multi-line anonymous functions