Add symbol-to-proc mutations

- Adds mutations like `map(&:to_s)` -> `map(&:to_str)`.

Changelog.md

@@ -1,5 +1,6 @@
 # Unreleased
 
+* Add symbol-to-proc block mutations (`map(&:to_s)` -> `map(&to_str)`) [#1048](https://github.com/mbj/mutant/pull/1048)
 * Add block-pass mutations (`foo(&method(:bar))` -> `foo(&public_method(:bar))`) [#1047](https://github.com/mbj/mutant/pull/1047)
 * Add new mutation of `Array(foo)` -> `[foo]` [#1043](https://github.com/mbj/mutant/pull/1043)
 * Add new mutation to mutate dynamic sends to static sends ({`foo.__send__(:bar)`, `foo.send(:bar)`, `foo.public_send(:bar)`} -> `foo.bar`) [#1040](https://github.com/mbj/mutant/pull/1040) and [#1049](https://github.com/mbj/mutant/pull/1049)

lib/mutant/mutator/node/block_pass.rb

@@ -13,6 +13,15 @@ class BlockPass < self
 
         def dispatch
           emit_argument_mutations
+          emit_symbol_to_proc_mutations
+        end
+
+        def emit_symbol_to_proc_mutations
+          return unless n_sym?(argument)
+
+          Send::SELECTOR_REPLACEMENTS.fetch(*argument, EMPTY_ARRAY).each do |method|
+            emit_argument(s(:sym, method))
+          end
         end
       end # Block
     end # Node

meta/block_pass.rb

@@ -23,3 +23,24 @@
   mutation 'foo(&public_method(:bar))'
   mutation 'foo(&:bar)'
 end
+
+Mutant::Meta::Example.add :block_pass do
+  source 'foo(&:to_s)'
+
+  singleton_mutations
+  mutation 'foo'
+  mutation 'foo(&nil)'
+  mutation 'foo(&self)'
+  mutation 'foo(&:to_str)'
+  mutation 'foo(&:to_s__mutant__)'
+end
+
+Mutant::Meta::Example.add :block_pass do
+  source 'foo(&:bar)'
+
+  singleton_mutations
+  mutation 'foo'
+  mutation 'foo(&nil)'
+  mutation 'foo(&self)'
+  mutation 'foo(&:bar__mutant__)'
+end