Don't consider concept types as non-complex during codegen (#8119)

Fixes #7125

tests/concepts/tmisc_issues.nim

@@ -9,7 +9,8 @@ implicit generic
 generic
 false
 true
--1'''
+-1
+Meow'''
 """
 
 # https://github.com/nim-lang/Nim/issues/1147
@@ -98,3 +99,15 @@ let b = B()
 echo b is A
 echo b.size()
 
+# https://github.com/nim-lang/Nim/issues/7125
+type
+  Thing = concept x
+    x.hello is string
+  Cat = object
+
+proc hello(d: Cat): string = "Meow"
+
+proc sayHello(c: Thing) = echo(c.hello)
+
+var a: Thing = Cat()
+a.sayHello()