Allow the short form "cdef struct xyz: pass" instead of always requiring a block for it.

Closes #2802.

Cython/Compiler/Parsing.py

@@ -3184,9 +3184,13 @@ def p_c_struct_or_union_definition(s, pos, ctx):
     attributes = None
     if s.sy == ':':
         s.next()
+        attributes = []
+        if s.sy == 'pass':
+            s.next()
+            s.expect_newline("Expected a newline", ignore_semicolon=True)
+        else:
             s.expect('NEWLINE')
             s.expect_indent()
-        attributes = []
             body_ctx = Ctx()
             while s.sy != 'DEDENT':
                 if s.sy != 'pass':

tests/broken/cdefemptysue.pyx

-cdef extern from "cdefemptysue.h":
-
-    cdef struct spam:
-        pass
-
-    ctypedef union eggs:
-        pass
-
-    cdef enum ham:
-        pass
-
-cdef extern spam s
-cdef extern eggs e
-cdef extern ham h

tests/compile/cdefemptysue.pyx

+# mode: compile
+# tag: struct, union, enum, cdefextern
+
+cdef extern from *:
+    """
+    struct spam { int a; };
+    struct flat_spam { int a; };
+    typedef struct { int a; } flat_spam_type;
+
+    typedef union { int a; long b; } eggs;
+    typedef union { int a; long b; } flat_eggs;
+
+    enum ham { TOAST };
+    enum flat_ham { FLAT_TOAST };
+    """
+
+    cdef struct spam:
+        pass
+
+    cdef struct flat_spam: pass
+
+    ctypedef struct flat_spam_type: pass
+
+    ctypedef union eggs:
+        pass
+
+    ctypedef union flat_eggs: pass
+
+    cdef enum ham:
+        pass
+
+    cdef enum flat_ham: pass
+
+
+cdef extern spam s
+cdef extern flat_spam fs
+cdef extern flat_spam_type fst
+
+cdef extern eggs e
+cdef extern flat_eggs fe
+
+cdef extern ham h
+cdef extern flat_ham fh

tests/broken/cdefexternblock.pyx → tests/compile/cdefexternblock.pyx

+# mode: compile
+# tag: struct, union, enum, cdefextern
+
 cdef extern from "cheese.h":
 
     ctypedef int camembert
@@ -9,11 +12,12 @@ cdef extern from "cheese.h":
 
     void cheddar()
 
-    class external.runny [object runny_obj]:
-        cdef int a
-        def __init__(self):
-            pass
+    # FIXME: find a real declaration here.
+    #class external.runny [object runny_obj]:
+    #    cdef int a
+    #    def __init__(self):
+    #        pass
+
 
-cdef runny r
-r = x
-r.a = 42
+#cdef runny r = runny()
+#r.a = 42

tests/errors/e_cdefemptysue.pyx

@@ -8,8 +8,21 @@ ctypedef union eggs:
 
 cdef enum ham:
 	pass
+
+
+cdef struct flat_spam: pass
+
+ctypedef union flat_eggs: pass
+
+cdef enum flat_ham: pass
+
+
 _ERRORS = u"""
 3:5: Empty struct or union definition not allowed outside a 'cdef extern from' block
 6:0: Empty struct or union definition not allowed outside a 'cdef extern from' block
 9:5: Empty enum definition not allowed outside a 'cdef extern from' block
+
+13:5: Empty struct or union definition not allowed outside a 'cdef extern from' block
+15:0: Empty struct or union definition not allowed outside a 'cdef extern from' block
+17:5: Empty enum definition not allowed outside a 'cdef extern from' block
 """