The TypeRef name comes from IntelliJ days, where you often have both
type *syntax* as well as *semantical* representation of types in
scope. And naming both Type is confusing.
In rust-analyzer however, we use ast types as `ast::Type`, and have
many more semantic counterparts to ast types, so avoiding name clash
here is just confusing.
If any rules contain paths, then we reject any rules that don't contain paths. Allowing a mix leads to strange semantics, since the path-based rules only match things where the path refers to semantically the same thing, whereas the non-path-based rules could match anything. Specifically, if we have a rule like `foo ==>> bar` we only want to match the `foo` that is in the current scope, not any `foo`. However "foo" can be parsed as a pattern (BIND_PAT -> NAME -> IDENT). Allowing such a rule through would result in renaming everything called `foo` to `bar`. It'd also be slow, since without a path, we'd have to use the slow-scan search mechanism.
This is in preparation for a subsequent commit where we add special
handling for paths in the template, allowing them to be qualified
differently in different contexts.
Previously we had:
- Multiple rules
- Each rule had its pattern parsed as an expression, path etc
This meant that there were two levels at which there could be multiple
rules.
Now we just have multiple rules. If a pattern can parse as more than one
kind of thing, then they get stored as multiple separate rules.
We also now don't have separate fields for the different kinds of things
that a pattern can parse as. This makes adding new kinds of things
simpler.
Previously, add_search_pattern would construct a rule with a dummy
replacement. Now the replacement is an Option. This is slightly cleaner
and also opens the way for parsing the replacement template as the same
kind of thing as the search pattern.
