From 26e8a598be2a221f469e3c501b72c5986764fabc Mon Sep 17 00:00:00 2001
From: "Jeremy G. Siek" <jeremy.siek@gmail.com>
Date: Sat, 21 Dec 2024 15:06:34 -0500
Subject: [PATCH] improved error for print and parenthesized term

---
 rec_desc_parser.py                  | 18 ++++++++++++++----
 test/should-error/paren_term.pf     |  9 +++++++++
 test/should-error/paren_term.pf.err |  8 ++++++++
 3 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 test/should-error/paren_term.pf
 create mode 100644 test/should-error/paren_term.pf.err

diff --git a/rec_desc_parser.py b/rec_desc_parser.py
index 1b3dc40..39b5588 100644
--- a/rec_desc_parser.py
+++ b/rec_desc_parser.py
@@ -250,11 +250,14 @@ def parse_term_hi():
     
   elif token.type == 'LPAR':
     advance()
+    while_parsing = 'while parsing parenthesized term\n' \
+        + '\tterm ::= "(" term ")"\n'
+
     term = parse_term()
     if current_token().type != 'RPAR':
       error(meta_from_tokens(current_token(), current_token()),
             'expected closing parentheses, not\n\t' \
-            + current_token().value)
+            + current_token().value + '\n' + while_parsing)
     advance()
     return term
 
@@ -1307,10 +1310,17 @@ def parse_statement():
     name = parse_identifier()
     return Import(meta_from_tokens(token, previous_token()), name)
   elif token.type == 'PRINT':
+    while_parsing = 'while parsing\n' \
+        + '\tstatement ::= "print" term\n'
     advance()
-    subject = parse_term()
-    meta = meta_from_tokens(token, previous_token())
-    return Print(meta, subject)
+    try:
+        subject = parse_term()
+        meta = meta_from_tokens(token, previous_token())
+        return Print(meta, subject)
+    except Exception as e:
+        meta = meta_from_tokens(token, previous_token())
+        raise Exception(str(e) + '\n' + error_header(meta) + while_parsing)
+        
   elif token.type == 'THEOREM' or token.type == 'LEMMA':
     return parse_theorem()
   elif token.type == 'UNION':
diff --git a/test/should-error/paren_term.pf b/test/should-error/paren_term.pf
new file mode 100644
index 0000000..40443d8
--- /dev/null
+++ b/test/should-error/paren_term.pf
@@ -0,0 +1,9 @@
+import Nat
+import List
+
+function sum(List<Nat>) -> Nat {
+  sum([]) = 0
+  sum(node(x, xs)) = x + sum(xs)
+}
+
+print(sum, [1,2,3])
diff --git a/test/should-error/paren_term.pf.err b/test/should-error/paren_term.pf.err
new file mode 100644
index 0000000..dd2c472
--- /dev/null
+++ b/test/should-error/paren_term.pf.err
@@ -0,0 +1,8 @@
+./test/should-error/paren_term.pf:9.10-9.11: expected closing parentheses, not
+	,
+while parsing parenthesized term
+	term ::= "(" term ")"
+
+./test/should-error/paren_term.pf:9.1-9.10: while parsing
+	statement ::= "print" term
+