doc: Document debugging tips (#214)

.github/FUNDING.yml

@@ -1,3 +1,4 @@
 # These are supported funding model platforms
 
 github: kdy1
+open_collective: stc

CONTRIBUTING.md

@@ -30,6 +30,36 @@ It will dump type information to a `foo.swc-stderr` file.
 Look at it, and if it's wrong, adjust the Rust source code, and run `./scripts/check.sh` to verify if your fix is correct.
 If you are done, please file a pull request on GitHub.
 
+### Directories for testing
+
+See [the readme of the file analyzer](./crates/stc_ts_file_analyzer/) for more details.
+
+### Debugging tips
+
+#### `print_backtrace()`
+
+If you think some code should not be invoked but seems like it's invoked, you can use `print_backtrace()`.
+It will automatically exclude useless items from the stack trace.
+
+#### Matching over `Type`
+
+To avoid performance drop caused by cloning, stc uses `Type::Arc` to share memory.
+But there's a downside for this - you have to call `normalize()` while matching.
+
+e.g.
+
+```rust
+match ty.normalize() {
+}
+```
+
+Note that this is different from `self.normalize(ty)` of `Analyzer`, which is used to expand special types like references, queries, mapped, etc..
+
+#### Finding problematic code
+
+Look at the `context:` in the error output, and search it from repository using substring of the context.
+e.g. `tried to assign to a template type` means the error comes from https://github.com/dudykr/stc/blob/1c73ce5fa87ec789ead108c5c6876e8089b1e5de/crates/stc_ts_file_analyzer/src/analyzer/assign/mod.rs#L2208
+
 ### Updating performance stats
 
 You can run `./scripts/release-time.sh` from `./crates/stc_ts_type_checker` to update timing stats file.

cspell.json

@@ -13,6 +13,7 @@
         "dedup",
         "dejavu",
         "deps",
+        "dudykr",
         "elems",
         "fastpath",
         "fxhash",