2 files changed, 42 insertions, 0 deletions
diff --git a/Test/triggers/useless-triggers-are-removed.dfy b/Test/triggers/useless-triggers-are-removed.dfy
new file mode 100644
index 00000000..16458e41
--- /dev/null
+++ b/Test/triggers/useless-triggers-are-removed.dfy
@@ -0,0 +1,25 @@
+// RUN: %dafny /printTooltips /compile:0 /print:"%t.print" /dprint:"%t.dprint" /autoTriggers:1 "%s" > "%t"
+// RUN: %diff "%s.expect" "%t"
+
+// This file ensures that Dafny does get rid of redundant triggers before
+// annotating a quantifier, and that ths process does not interfere with cycle
+// detection.
+
+function f(x: int): int
+function g(x: int): int
+function h(x: int): int
+
+method M()
+  // In the following, only f(x) is kept. Note that the subset enumeration was
+  // already smart enough to not build any trigger with multiple terms (it only
+  // built 5 candidates)
+  requires forall x: int :: f(x) + g(f(x)) + h(f(x)) + g(h(f(x))) + h(g(f(x))) == 0
+
+  // Loop detection still works fine: in the following example, the trigger is
+  // f(f(x))
+  requires forall x: int :: f(x) == f(f(x))
+
+  // This works for multi-triggers, too:
+  requires forall x, y :: f(x) + g(f(y)) + g(y) + g(f(x)) == 0
+{
+}
diff --git a/Test/triggers/useless-triggers-are-removed.dfy.expect b/Test/triggers/useless-triggers-are-removed.dfy.expect
new file mode 100644
index 00000000..6c2c0a2b
--- /dev/null
+++ b/Test/triggers/useless-triggers-are-removed.dfy.expect
@@ -0,0 +1,17 @@
+useless-triggers-are-removed.dfy(16,11): Info: Selected triggers: {f(x)}
+ Rejected triggers:
+   {h(g(f(x)))} (stronger than {g(f(x))}, {f(x)})
+   {g(h(f(x)))} (stronger than {h(f(x))}, {f(x)})
+   {h(f(x))} (stronger than {f(x)})
+   {g(f(x))} (stronger than {f(x)})
+useless-triggers-are-removed.dfy(20,11): Info: Selected triggers: {f(f(x))}
+ Rejected triggers: {f(x)} (loops with {f(f(x))})
+useless-triggers-are-removed.dfy(23,11): Info: Selected triggers:
+   {g(f(x)), g(y)}, {f(y), f(x)}
+ Rejected triggers:
+   {g(y), f(x)} (loops with {g(f(y))}, {g(f(x))})
+   {g(f(x)), g(f(y))} (stronger than {g(f(x)), f(y)}, {g(f(y)), f(x)}, {f(y), f(x)})
+   {g(f(x)), f(y)} (stronger than {f(y), f(x)})
+   {g(f(y)), f(x)} (stronger than {f(y), f(x)})
+
+Dafny program verifier finished with 5 verified, 0 errors