Commits on Nov 7, 2021

1. ruleguard: add support for local functions …

   This feature is useful for rule filters readability improvements.
   
   Instead of copying a complex `Where()` expression several times,
   one can now use a local function literal to define that filter
   operation and use it inside `Where()` expressions.
   
   Here is an example:
   
   ```go
   func preferFprint(m dsl.Matcher) {
   	isFmtPackage := func(v dsl.Var) bool {
   		return v.Text == "fmt" && v.Object.Is(`PkgName`)
   	}
   
   	m.Match(`$w.Write([]byte($fmt.Sprint($*args)))`).
   		Where(m["w"].Type.Implements("io.Writer") && isFmtPackage(m["fmt"])).
   		Suggest("fmt.Fprint($w, $args)").
   		Report(`fmt.Fprint($w, $args) should be preferred to the $$`)
   
   	m.Match(`$w.Write([]byte($fmt.Sprintf($*args)))`).
   		Where(m["w"].Type.Implements("io.Writer") && isFmtPackage(m["fmt"])).
   		Suggest("fmt.Fprintf($w, $args)").
   		Report(`fmt.Fprintf($w, $args) should be preferred to the $$`)
   
   	// ...etc
   }
   ```
   
   Note that we used `isFmtPackage` in more than 1 rule.
   
   Functions can accept almost arbitrary params, but there are some
   restrictions on what kinds of arguments they can receive right now.
   
   These arguments work:
   
   * Matcher var expressions like `m["varname"]`
   * Basic literals like `"foo"`, `104`, `5.2`
   * Constants

   

   quasilyte committed Nov 7, 2021
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