[ty] name is parameter and global is a syntax error (#21312)

Co-authored-by: Alex Waygood <alex.waygood@gmail.com>
Co-authored-by: Brent Westbrook <36778786+ntBre@users.noreply.github.com>

crates/ty_python_semantic/resources/mdtest/diagnostics/semantic_syntax_errors.md

@@ -376,3 +376,41 @@ for x in range(42):
         break  # error: [invalid-syntax]
         continue  # error: [invalid-syntax]
 ```
+
+## name is parameter and global
+
+<!-- snapshot-diagnostics -->
+
+```py
+a = None
+
+def f(a):
+    global a  # error: [invalid-syntax]
+
+def g(a):
+    if True:
+        global a  # error: [invalid-syntax]
+
+def h(a):
+    def inner():
+        global a
+
+def i(a):
+    try:
+        global a  # error: [invalid-syntax]
+    except Exception:
+        pass
+
+def f(a):
+    a = 1
+    global a  # error: [invalid-syntax]
+
+def f(a):
+    a = 1
+    a = 2
+    global a  # error: [invalid-syntax]
+
+def f(a):
+    class Inner:
+        global a  # ok
+```