Flowistry is a VSCode extension that helps developers understand Rust programs. Flowistry uses dataflow analysis and pointer analysis to analyze Rust programs at a deeper semantic level than just types can offer.
Flowistry is alpha software (see Limitations). I'm seeking early adopters to try it out and provide feedback!
Flowistry's capabilities are:
A backward slice identifies every piece of code that affects a value of interest. For example, let's say you're debugging an assertion failure on x. Then you could compute the backward slice of x to rule out lines of code that don't influence its value, as shown here:
A forward slice identifiers every piece of code that is affected by a value of interest. For example, let's say you have a program that times a calculation, and you want to find all the code related to timing. You could compute a forward slice of the timer to rule out the actual calculation:
A function's effects are either inputs that it mutates, or values that it returns. The function effects panel helps identify lines of code that either mutate arguments or return values. Selecting an effect then shows the backward slice of that effect.
You can install Flowistry from the Visual Studio Marketplace. Alternatively, you can install it from source:
```
rustup toolchain install nightly -c rust-src,rustc-dev,llvm-tools-preview git clone https://github.com/willcrichton/flowistry cd flowistry cargo +nightly install --path .
cd ide npm run install npm run build ln -s $(pwd) ~/.vscode/extensions/flowistry ```
In VSCode, Flowistry is invoked from the Command Palette. On Mac, this is opened with ⇧⌘P. Then you can invoke one of these commands: * Flowistry: Backward Highlight: given a selected variable, this command highlights the backward slice of the variable. * Flowistry: Backward Select: same as above, but this puts the slice in your selection rather than highlighting it. * Flowistry: Forward Highlight and Flowistry: Forward Select: same as above, but for forward slices than backward slices. * Flowistry: Effects: given your cursor is within a particular function, this command opens the effects panel for that function.
Flowistry is early-stage software. It inevitably has bugs in both the UI and the analysis. The UI may be unintuitive. The analysis, even if correct, may also be unintuitive. Additionally, Flowistry only works on code compiled with the nightly Rust compiler.