tree 5051c2da8e5bd9c6b811ff62259e5abe63b511d5
parent 75ae018a5b9214a375d0acbd7bd657e534a0bde2
author Mitch Rudominer <rudominer@chromium.org> 1461891766 -0700
committer Mitch Rudominer <rudominer@chromium.org> 1461891766 -0700

Mojom frontend: Detect Ill-founded Types

This patch adds the functionality to detect user-defined types that are unserializable because every instance of the type would contain a cycle.

We use the ill-founded node detection algorithm from https://codereview.chromium.org/1908273003/ by having UserDefinedTypeBase implement the |Node| interface.

- In mojom_descriptor.go we add the method DetectIllFoundedTypes()
- We Invoke DetectIllFoundedTypes()in parse_driver.go after ComputeFinalData()
- We add the method NonAvoidableUserDefinedType() to the TypeRef interface to capture the notion that a type reference unavoidably entails a non-null pointer to a struct or union.
-We fixed up some ill-founded types that appeared in serialization_test.go because now we would be detecting them and failing before serialization.
- We enhanced the ill-founded graph detection library (in wellfounded_graphs.go) by introducing the ability for the client to add labels to the edges. The labels are opaque to the algorithm but we use them to maintain enough information to generate a useful error message. For example we use them to capture the name of the struct or union field corresponding to a graph edge.
- See illfounded_types_test.go to see the format of the error messages we will emit when an ill-founded type is detected.

BUG= fixes #694
R=azani@chromium.org

Review URL: https://codereview.chromium.org/1915413002 .