Repair string forward references to extension types in cython.locals() decorator.

CHANGES.rst

@@ -8,6 +8,9 @@ Cython Changelog
 Bugs fixed
 ----------
 
+* String forward references to extension types like ``@cython.locals(x="ExtType")``
+  failed to find the named type.  (Github issue #1962)
+
 * NumPy slicing generated incorrect results when compiled with Pythran.
   (Github issue #1946)
 

Cython/Compiler/ExprNodes.py

@@ -1362,6 +1362,11 @@ def _analyse_name_as_type(name, pos, env):
     type = PyrexTypes.parse_basic_type(name)
     if type is not None:
         return type
+
+    global_entry = env.global_scope().lookup_here(name)
+    if global_entry and global_entry.type and global_entry.type.is_extension_type:
+        return global_entry.type
+
     from .TreeFragment import TreeFragment
     with local_errors(ignore=True):
         pos = (pos[0], pos[1], pos[2]-7)

tests/run/pure.pyx

@@ -160,3 +160,23 @@ def test_declare_c_types(n):
     #z01 = cython.declare(cython.floatcomplex, n+1j)
     #z02 = cython.declare(cython.doublecomplex, n+1j)
     #z03 = cython.declare(cython.longdoublecomplex, n+1j)
+
+
+cdef class ExtType:
+    """
+    >>> x = ExtType()
+    >>> x.forward_ref(x)
+    'ExtType'
+    """
+    @cython.locals(x="ExtType")
+    def forward_ref(self, x):
+        return cython.typeof(x)
+
+
+def ext_type_string_ref(x: "ExtType"):
+    """
+    >>> x = ExtType()
+    >>> ext_type_string_ref(x)
+    'ExtType'
+    """
+    return cython.typeof(x)