fix #17911 rawProc for cpp (#17912)

tests/stdlib/tsystem.nim

@@ -0,0 +1,46 @@
+discard """
+  targets: "c cpp js"
+"""
+
+# TODO: in future work move existing `system` tests here, where they belong
+
+import stdtest/testutils
+
+template main =
+  block: # closure
+    proc outer() =
+      var a = 0
+      proc inner1 = a.inc
+      proc inner2 = discard
+      doAssert inner1 is "closure"
+      doAssert inner2 isnot "closure"
+      doAssert inner1 is (proc)
+      doAssert inner2 is (proc)
+      let inner1b = inner1
+      doAssert inner1b is "closure"
+      doAssert inner1b == inner1
+    outer()
+
+  block: # rawProc, rawProc, bug #17911
+    proc outer() =
+      var a = 0
+      var b = 0
+      proc inner1() = a.inc
+      proc inner2() = a += 2
+      proc inner3() = b.inc
+      let inner1b = inner1
+      doAssert inner2 != inner1
+      doAssert inner3 != inner1
+      whenVMorJs: discard
+      do:
+        doAssert rawProc(inner1b) == rawProc(inner1)
+        doAssert rawProc(inner2) != rawProc(inner1)
+        doAssert rawProc(inner3) != rawProc(inner1)
+
+        doAssert rawEnv(inner1b) == rawEnv(inner1)
+        doAssert rawEnv(inner2) == rawEnv(inner1) # because both use `a`
+        # doAssert rawEnv(inner3) != rawEnv(inner1) # because `a` vs `b` # this doesn't hold
+    outer()
+
+static: main()
+main()