- Harden coverage generation, by not attempting to compile

runtime/vm/coverage.cc

Index: runtime/vm/coverage.cc
===================================================================
--- runtime/vm/coverage.cc	(revision 28280)
+++ runtime/vm/coverage.cc	(working copy)
@@ -21,9 +21,25 @@
 void CodeCoverage::CompileAndAdd(const Function& function,
                                  const JSONArray& hits_arr) {
   if (!function.HasCode()) {
-    if (Compiler::CompileFunction(function) != Error::null()) {
+    // If the function should not be compiled or if the compilation failed,
+    // then just skip this method.
+    // TODO(iposva): Maybe we should skip synthesized methods in general too.
+    if (function.is_abstract() || function.IsRedirectingFactory()) {
       return;
     }
+    if (function.IsNonImplicitClosureFunction() &&
+        (function.context_scope() == ContextScope::null())) {
+      // TODO(iposva): This can arise if we attempt to compile an inner function
+      // before we have compiled its enclosing function or if the enclosing
+      // function failed to compile.
+      OS::Print("### Coverage skipped compiling: %s\n", function.ToCString());
+      return;
+    }
+    const Error& err = Error::Handle(Compiler::CompileFunction(function));
+    if (!err.IsNull()) {
+      OS::Print("### Coverage failed compiling:\n%s\n", err.ToErrorCString());
+      return;
+    }
   }
   ASSERT(function.HasCode());