1 files changed, 74 insertions, 0 deletions
diff --git a/drnim/tests/tensures.nim b/drnim/tests/tensures.nim
new file mode 100644
index 000000000..f4e8f84e6
--- /dev/null
+++ b/drnim/tests/tensures.nim
@@ -0,0 +1,74 @@
+discard """
+  nimout: '''tensures.nim(18, 10) Warning: BEGIN [User]
+tensures.nim(27, 5) Warning: cannot prove:
+0 < n [IndexCheck]
+tensures.nim(47, 17) Warning: cannot prove: a < 4; counter example: y -> 2
+a`2 -> 4
+a`1 -> 3
+a -> 2 [IndexCheck]
+tensures.nim(69, 17) Warning: cannot prove: a < 4; counter example: y -> 2
+a`1 -> 4
+a -> 2 [IndexCheck]
+tensures.nim(73, 10) Warning: END [User]'''
+  cmd: "drnim $file"
+  action: "compile"
+"""
+import std/logic
+{.push staticBoundChecks: defined(nimDrNim).}
+{.warning: "BEGIN".}
+
+proc fac(n: int) {.requires: n > 0.} =
+  discard
+
+proc g(): int {.ensures: result > 0.} =
+  result = 10
+
+fac 7 # fine
+fac -45 # wrong
+
+fac g() # fine
+
+proc main =
+  var x = g()
+  fac x
+
+main()
+
+proc myinc(x: var int) {.ensures: x == old(x)+1.} =
+  inc x
+  {.assume: old(x)+1 == x.}
+
+proc mainB(y: int) =
+  var a = y
+  if a < 3:
+    myinc a
+    {.assert: a < 4.}
+    myinc a
+    {.assert: a < 4.} # now this is wrong!
+
+mainB(3)
+
+proc a(yy, z: int) {.requires: (yy - z) > 6.} = discard
+# 'requires' must be weaker (or equal)
+# 'ensures'  must be stronger (or equal)
+
+# a 'is weaker than' b iff  b -> a
+# a 'is stronger than' b iff a -> b
+# --> We can use Z3 to compute whether 'var x: T = q' is valid
+
+type
+  F = proc (yy, z3: int) {.requires: z3 < 5 and z3 > -5 and yy > 10.}
+
+var
+  x: F = a # valid?
+
+proc testAsgn(y: int) =
+  var a = y
+  if a < 3:
+    a = a + 2
+    {.assert: a < 4.}
+
+testAsgn(3)
+
+{.warning: "END".}
+{.pop.}