Improve error reporting when users mistakenly write "&&" or "||" instead of...

Improve error reporting when users mistakenly write "&&" or "||" instead of Python's "and" and "or" operators. (GH-3858)

Cython/Compiler/Lexicon.py

@@ -77,7 +77,7 @@ def make_lexicon():
     punct = Any(":,;+-*/|&<>=.%`~^?!@")
     diphthong = Str("==", "<>", "!=", "<=", ">=", "<<", ">>", "**", "//",
                     "+=", "-=", "*=", "/=", "%=", "|=", "^=", "&=",
-                    "<<=", ">>=", "**=", "//=", "->", "@=", "&&")
+                    "<<=", ">>=", "**=", "//=", "->", "@=", "&&", "||")
     spaces = Rep1(Any(" \t\f"))
     escaped_newline = Str("\\\n")
     lineterm = Eol + Opt(Str("\n"))

Cython/Compiler/Parsing.pxd

@@ -26,7 +26,7 @@ cdef p_lambdef_nocond(PyrexScanner s)
 cdef p_test(PyrexScanner s)
 cdef p_test_nocond(PyrexScanner s)
 cdef p_or_test(PyrexScanner s)
-cdef p_rassoc_binop_expr(PyrexScanner s, ops, p_sub_expr_func p_subexpr)
+cdef p_rassoc_binop_expr(PyrexScanner s, unicode op, p_sub_expr_func p_subexpr)
 cdef p_and_test(PyrexScanner s)
 cdef p_not_test(PyrexScanner s)
 cdef p_comparison(PyrexScanner s)

Cython/Compiler/Parsing.py

@@ -14,7 +14,7 @@ cython.declare(Nodes=object, ExprNodes=object, EncodedString=object,
                Builtin=object, ModuleNode=object, Utils=object, _unicode=object, _bytes=object,
                re=object, sys=object, _parse_escape_sequences=object, _parse_escape_sequences_raw=object,
                partial=object, reduce=object, _IS_PY3=cython.bint, _IS_2BYTE_UNICODE=cython.bint,
-               _CDEF_MODIFIERS=tuple)
+               _CDEF_MODIFIERS=tuple, COMMON_BINOP_MISTAKES=dict)
 
 from io import StringIO
 import re
@@ -159,24 +159,31 @@ def p_test_nocond(s):
 
 #or_test: and_test ('or' and_test)*
 
+COMMON_BINOP_MISTAKES = {'||': 'or', '&&': 'and'}
+
 def p_or_test(s):
-    return p_rassoc_binop_expr(s, ('or',), p_and_test)
+    return p_rassoc_binop_expr(s, u'or', p_and_test)
 
-def p_rassoc_binop_expr(s, ops, p_subexpr):
+def p_rassoc_binop_expr(s, op, p_subexpr):
     n1 = p_subexpr(s)
-    if s.sy in ops:
+    if s.sy == op:
         pos = s.position()
         op = s.sy
         s.next()
-        n2 = p_rassoc_binop_expr(s, ops, p_subexpr)
+        n2 = p_rassoc_binop_expr(s, op, p_subexpr)
         n1 = ExprNodes.binop_node(pos, op, n1, n2)
+    elif s.sy in COMMON_BINOP_MISTAKES and COMMON_BINOP_MISTAKES[s.sy] == op:
+        # Only report this for the current operator since we pass through here twice for 'and' and 'or'.
+        warning(s.position(),
+                "Found the C operator '%s', did you mean the Python operator '%s'?" % (s.sy, op),
+                level=1)
     return n1
 
 #and_test: not_test ('and' not_test)*
 
 def p_and_test(s):
     #return p_binop_expr(s, ('and',), p_not_test)
-    return p_rassoc_binop_expr(s, ('and',), p_not_test)
+    return p_rassoc_binop_expr(s, u'and', p_not_test)
 
 #not_test: 'not' not_test | comparison
 

tests/errors/e_binop_and.pyx

+# mode: error
+# tag: and, binop, warnings
+
+def test_and(a, b):
+    return a && b
+
+
+_WARNINGS = """
+5:13: Found the C operator '&&', did you mean the Python operator 'and'?
+"""
+
+_ERRORS = """
+5:13: Syntax error in simple statement list
+"""

tests/errors/e_binop_or.pyx

+# mode: error
+# tag: or, binop, warnings
+
+def test_or(a, b):
+    return a || b
+
+
+_WARNINGS = """
+5:13: Found the C operator '||', did you mean the Python operator 'or'?
+"""
+
+_ERRORS = """
+5:13: Syntax error in simple statement list
+"""