From 71614585f5a36e0a8f196db10cce610b9ab2da23 Mon Sep 17 00:00:00 2001
From: Christopher Chang <51393127+chriscerie@users.noreply.github.com>
Date: Sat, 14 Oct 2023 11:21:58 -0700
Subject: [PATCH] Skip fixing unused variable when they have references

---
 selene-lib/src/lints/unused_variable.rs                  | 7 +++++++
 selene-lib/tests/lints/unused_variable/blocks.fixed.diff | 9 +++------
 .../tests/lints/unused_variable/edge_cases.fixed.diff    | 6 ++----
 selene-lib/tests/lints/unused_variable/locals.fixed.diff | 6 ++----
 .../tests/lints/unused_variable/observes.fixed.diff      | 9 +++------
 .../tests/lints/unused_variable/write_only.fixed.diff    | 3 +--
 6 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/selene-lib/src/lints/unused_variable.rs b/selene-lib/src/lints/unused_variable.rs
index 71a0e613..2f5da454 100644
--- a/selene-lib/src/lints/unused_variable.rs
+++ b/selene-lib/src/lints/unused_variable.rs
@@ -172,6 +172,13 @@ impl Lint for UnusedVariableLint {
                     fixed_code = None;
                 }
 
+                // Applying fix would cause references to reference the old variable. It's possible to also rename those
+                // references as well, but we'd need to check each of their scopes for potentially colliding variables.
+                // Cargo just doesn't apply a fix in these cases.
+                if !variable.references.is_empty() {
+                    fixed_code = None;
+                }
+
                 let write_only = !analyzed_references.is_empty();
 
                 diagnostics.push(Diagnostic::new_complete(
diff --git a/selene-lib/tests/lints/unused_variable/blocks.fixed.diff b/selene-lib/tests/lints/unused_variable/blocks.fixed.diff
index 5308ebc1..402db837 100644
--- a/selene-lib/tests/lints/unused_variable/blocks.fixed.diff
+++ b/selene-lib/tests/lints/unused_variable/blocks.fixed.diff
@@ -1,15 +1,12 @@
  -- Functions
 -local function unusedFunction()
--    local unusedVariableA = 1
--    local unusedVariableB = 1
 +local function _unusedFunction()
-+    local _unusedVariableA = 1
-+    local _unusedVariableB = 1
+     local unusedVariableA = 1
+     local unusedVariableB = 1
  end
  
  print(unusedVariableB)
--local overidden = true
-+local _overidden = true
+ local overidden = true
  
  local function overridesIt()
      local overidden = false
diff --git a/selene-lib/tests/lints/unused_variable/edge_cases.fixed.diff b/selene-lib/tests/lints/unused_variable/edge_cases.fixed.diff
index 414306c0..8565d0c6 100644
--- a/selene-lib/tests/lints/unused_variable/edge_cases.fixed.diff
+++ b/selene-lib/tests/lints/unused_variable/edge_cases.fixed.diff
@@ -1,8 +1,6 @@
  local foo = 1
--local foo = foo + 1
--local bar = bar
-+local _foo = foo + 1
-+local _bar = bar
+ local foo = foo + 1
+ local bar = bar
  
  -- The variables inside of a repeat...until are accessible from the until statement
  repeat
diff --git a/selene-lib/tests/lints/unused_variable/locals.fixed.diff b/selene-lib/tests/lints/unused_variable/locals.fixed.diff
index ea6cec85..6bcc77e7 100644
--- a/selene-lib/tests/lints/unused_variable/locals.fixed.diff
+++ b/selene-lib/tests/lints/unused_variable/locals.fixed.diff
@@ -7,8 +7,7 @@
  print(localC)
  
  -- Mutated, but never read
--local localD = 1
-+local _localD = 1
+ local localD = 1
  localD = 2
  localD = 3
  
@@ -29,5 +28,4 @@
  
  -- Put into a table
  local localH = 1
--local localI = { localH }
-+local _localI = { localH }
+ local localI = { localH }
diff --git a/selene-lib/tests/lints/unused_variable/observes.fixed.diff b/selene-lib/tests/lints/unused_variable/observes.fixed.diff
index 64c364f0..e62cc6fa 100644
--- a/selene-lib/tests/lints/unused_variable/observes.fixed.diff
+++ b/selene-lib/tests/lints/unused_variable/observes.fixed.diff
@@ -1,5 +1,4 @@
--local writtenOnlyA = {}
-+local _writtenOnlyA = {}
+ local writtenOnlyA = {}
  table.insert(writtenOnlyA, 3)
  
  local readA = {}
@@ -7,8 +6,7 @@
  
  -- Make sure doing it inside other statements doesn't trigger false negatives
  print(function()
--	local writtenOnlyB = {}
-+	local _writtenOnlyB = {}
+ 	local writtenOnlyB = {}
  	table.insert(writtenOnlyB, 1)
  
  	local readB = {}
@@ -16,8 +14,7 @@
  end)
  
  if true then
--	local writtenOnlyC = {}
-+	local _writtenOnlyC = {}
+ 	local writtenOnlyC = {}
  	table.insert(writtenOnlyC, 1)
  
  	local readC = {}
diff --git a/selene-lib/tests/lints/unused_variable/write_only.fixed.diff b/selene-lib/tests/lints/unused_variable/write_only.fixed.diff
index f0652f88..47262952 100644
--- a/selene-lib/tests/lints/unused_variable/write_only.fixed.diff
+++ b/selene-lib/tests/lints/unused_variable/write_only.fixed.diff
@@ -1,5 +1,4 @@
--local bad1 = {}
-+local _bad1 = {}
+ local bad1 = {}
  bad1.x = 1
  bad1.y = 2
  bad1["z"] = 1