Type checker: ignore LifetimeDependenceRequest in cycle diagnostic

When reporting the declarations that lead to a cycle, we end up printing an
extra "through reference here" on the function declaration:

class C2: C1, P {
   |       |- note: through reference here
   |       `- note: through reference here
15 |     // expected-note@-1 2{{through reference here}}
16 |     override func run(a: A) {}
   |                   |   |  `- note: while resolving type 'A'
   |                   |   `- note: through reference here
   |                   |- error: circular reference
   |                   |- note: through reference here
   |                   `- note: through reference here

Author: atrick

lib/AST/Evaluator.cpp

@@ -127,6 +127,12 @@ void Evaluator::diagnoseCycle(const ActiveRequest &request) {
   for (const auto &step : llvm::reverse(activeRequests)) {
     if (step == request) return;
 
+    // Reporting the lifetime dependence location generates a redundant
+    // diagnostic.
+    if (step.getAs<LifetimeDependenceInfoRequest>()) {
+      continue;
+    }
+
     step.noteCycleStep(diags);
   }