Refactor repo into Cargo workspace with scaffolding for Rust-based qu…

…eries (#31)

## What Changed?

The repository has become a Cargo workspace. The new `crates` directory
contains:
- `dfpp`: PDG generation, same as before
- `dfpp-explorer`: the `dfpp/explorer` directory factored into a
standalone crate
- `dfgraph`: the core `ProgramDescription` type emitted by `dfpp`
- `dfcheck`: the runtime for property checkers

I also added a `props` directory at the root which contains sample
implementations of properties for Websubmit and Lemmy.

## Why Does It Need To?

To separate out the different concerns, and to ensure that third-party
property checkers don't need to include every `dfpp` transitive
dependency.

## Checklist

- [x] Above description has been filled out so that upon quash merge we
have a
  good record of what changed.
- [ ] New functions, methods, types are documented. Old documentation is
updated
  if necessary
- The new `dfcheck` and `dfcheck-cli` crates are not documented because
their structure is highly tentative.
- [ ] Documentation in Notion has been updated
  - Not sure where to update with this information?
- [ ] Tests for new behaviors are provided
- Need to add some tests that run the `dfcheck-cli` tool on the sample
properties.
- [ ] Refactor rustc serializers to just wholesale convert from rustc
types to ProgramDescription before any serialization happens

.github/workflows/rust.yml

@@ -40,12 +40,12 @@ jobs:
       run: cargo build --verbose
     - name: Run tests
       run: |
-        cargo test --test non_transitive_graph_tests 
-        cargo test --test call_chain_analysis_tests 
-        cargo test --test control_flow_tests
-        cargo test --test new_alias_analysis_tests
-        cargo test --test async_tests
-        cargo test --test inline_elision_tests
+        cargo test -p dfpp --test non_transitive_graph_tests 
+        cargo test -p dfpp --test call_chain_analysis_tests 
+        cargo test -p dfpp --test control_flow_tests
+        cargo test -p dfpp --test new_alias_analysis_tests
+        cargo test -p dfpp --test async_tests
+        cargo test -p dfpp --test inline_elision_tests
 
   intergration-tests:
     name: Integration Tests
@@ -77,7 +77,7 @@ jobs:
         cd forge
         raco pkg install --auto || raco setup forge
     - name: Run Tests
-      run: cargo test --test external_annotation_tests 
+      run: cargo test -p dfpp --test external_annotation_tests 
 
   format-check:
     name: Format Control
@@ -91,8 +91,11 @@ jobs:
       with:
         path: ~/.rustup
         key: ${{ runner.os }}-rust-toolchain-${{ hashFiles('rust-toolchain.toml') }}
-    - name: Perform Check
+    - name: Check main repo
       run: cargo fmt --check
+    - name: Check properties
+      run: cargo fmt --check
+      working-directory: props
 
   linting:
     name: Clippy
@@ -116,3 +119,6 @@ jobs:
         key: ${{ runner.os }}-rust-deps-${{ hashFiles('Cargo.lock', 'rust-toolchain.toml') }}
     - name: Here come the complaints
       run: cargo clippy --all -- -D warnings
+    - name: Complaints about properties
+      run: cargo clippy --all -- -D warnings
+      working-directory: props

.gitignore

@@ -1,4 +1,4 @@
-/target/
+target/
 
 
 /rust-dfpp-patch
@@ -7,4 +7,9 @@ flow-graph.json
 # Local cargo configuration
 .cargo/config.toml
 *.eqs
-*.info.json
+*.info.json
+
+props/Cargo.lock
+
+# Delete this if we want to include a rustfmt configuration
+.rustfmt.toml