Fix #3170: Allow priority 1200 operators in curly braces

Changed reduce_op(1199) to reduce_op(1200) to allow standard
priority 1200 operators like :- and --> in curly braces.

Per ISO Prolog §6.3.6, curly brackets contain a term which can
have operators up to priority 1200.

Tests now verify:
- Built-in operators (:-  and -->) work in curly braces
- User-defined priority 1200 operators work
- Priority 1199 operators work
- Parenthesized operators work
- Priority 1201 operators correctly rejected

J.J.'s Robot

Author: jjtolton

src/parser/parser.rs

@@ -773,7 +773,7 @@ impl<'a, R: CharRead> Parser<'a, R> {
             }
         }
 
-        self.reduce_op(1199);
+        self.reduce_op(1200);
 
         if self.stack.len() > 1 {
             if let Some(td) = self.stack.pop() {

tests/scryer/cli/issues/issue_3170_curly_operator.md

@@ -1,25 +1,51 @@
-# Issue #3170: Operators with priority 1200 should not be allowed in curly braces
+# Issue #3170: Curly brace operator priority limits
 
-## Test that priority 1200 operator in curly braces throws syntax error
+## Test that built-in priority 1200 operators work in curly braces
+
+### Test :- operator (priority 1200)
 
 ```trycmd
-$ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), op(1200,xfx,~>), read_from_chars(\"{a~>b}.\",T), halt"
-use_module(library(charsio)),op(1200,xfx,~>),read_from_chars("{a~>b}.",T),halt causes: error(syntax_error(incomplete_reduction),read_term_from_chars/3:0)
+$ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), read_from_chars(\"{a:-b}.\",T), writeq(T), nl, halt"
+{a:-b}
 
 ```
 
-## Test that priority 1199 operator in curly braces works
+### Test --> operator (priority 1200)
+
+```trycmd
+$ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), read_from_chars(\"{a-->b}.\",T), writeq(T), nl, halt"
+{a-->b}
+
+```
+
+## Test that user-defined priority 1200 operators work in curly braces
+
+```trycmd
+$ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), op(1200,xfx,~>), read_from_chars(\"{a~>b}.\",T), writeq(T), nl, halt"
+{a~>b}
+
+```
+
+## Test that priority 1199 operators work in curly braces
 
 ```trycmd
 $ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), op(1199,xfx,~>), read_from_chars(\"{a~>b}.\",T), writeq(T), nl, halt"
 {a~>b}
 
 ```
 
-## Test that parenthesized priority 1200 operator in curly braces works
+## Test that parenthesized priority 1200 operators work
 
 ```trycmd
 $ scryer-prolog -f --no-add-history -g "use_module(library(charsio)), op(1200,xfx,~>), read_from_chars(\"{(a~>b)}.\",T), writeq(T), nl, halt"
 {a~>b}
 
 ```
+
+## Test that priority 1201 operators fail (if definable)
+
+```trycmd
+$ scryer-prolog -f --no-add-history -g "op(1201,xfx,~>), halt"
+op(1201,xfx,~>),halt causes: error(domain_error(operator_priority,1201),op/3)
+
+```