[ruby/prism] Fix some type-checking errors by using different method calls

For example, use `.fetch` or `.dig` instead of `[]`, and use `===` instead of `is_a?` for checking types of objects.

https://github.com/ruby/prism/commit/548b54915f

3 files changed, 7 insertions, 5 deletions

diff --git a/lib/prism/parse_result.rb b/lib/prism/parse_result.rb
index 102567f59c..bd2349f60b 100644
--- a/lib/prism/parse_result.rb
+++ b/lib/prism/parse_result.rb
@@ -87,9 +87,9 @@ module Prism
 
       while left <= right
         mid = left + (right - left) / 2
-        return mid if offsets[mid] == byte_offset
+        return mid if (offset = offsets[mid]) == byte_offset
 
-        if offsets[mid] < byte_offset
+        if offset < byte_offset
           left = mid + 1
         else
           right = mid - 1
@@ -262,7 +262,7 @@ module Prism
 
     # Returns true if the given other location is equal to this location.
     def ==(other)
-      other.is_a?(Location) &&
+      Location === other &&
         other.start_offset == start_offset &&
         other.end_offset == end_offset
     end
@@ -541,7 +541,7 @@ module Prism
 
     # Returns true if the given other token is equal to this token.
     def ==(other)
-      other.is_a?(Token) &&
+      Token === other &&
         other.type == type &&
         other.value == value
     end
diff --git a/lib/prism/parse_result/newlines.rb b/lib/prism/parse_result/newlines.rb
index 927c17fe2f..03acb0b862 100644
--- a/lib/prism/parse_result/newlines.rb
+++ b/lib/prism/parse_result/newlines.rb
@@ -58,6 +58,8 @@ module Prism
 
     # Walk the tree and mark nodes that are on a new line.
     def mark_newlines!
+      value = self.value
+      raise "This method should only be called on a parse result that contains a node" unless Node === value
       value.accept(Newlines.new(Array.new(1 + source.offsets.size, false))) # steep:ignore
     end
   end
diff --git a/lib/prism/translation/parser/lexer.rb b/lib/prism/translation/parser/lexer.rb
index b710b1981b..bc7e77f291 100644
--- a/lib/prism/translation/parser/lexer.rb
+++ b/lib/prism/translation/parser/lexer.rb
@@ -302,7 +302,7 @@ module Prism
                 index += 1
               end
             when :tFID
-              if !tokens.empty? && tokens[-1][0] == :kDEF
+              if !tokens.empty? && tokens.dig(-1, 0) == :kDEF
                 type = :tIDENTIFIER
               end
             end