Change `typeDiff` to highlight changes less than 50%

2 files changed, 16 insertions, 11 deletions

diff --git a/src/dotty/tools/dotc/printing/Formatting.scala b/src/dotty/tools/dotc/printing/Formatting.scala
index 76d2bdc18..719c23e84 100644
--- a/src/dotty/tools/dotc/printing/Formatting.scala
+++ b/src/dotty/tools/dotc/printing/Formatting.scala
@@ -242,17 +242,17 @@ object Formatting {
     * correct `Context` for printing should also be passed when calling the
     * method.
     *
-    * @return the (found, expected) with coloring to highlight the difference
+    * @return the (found, expected, changePercentage) with coloring to
+    *         highlight the difference
     */
   def typeDiff(found: Type, expected: Type)(implicit ctx: Context): (String, String) = {
     val fnd = wrapNonSensical(found, found.show)
     val exp = wrapNonSensical(expected, expected.show)
 
-    (found, expected) match {
-      case (_: RefinedType, _: RefinedType) if ctx.settings.color.value != "never" =>
-        DiffUtil.mkColoredTypeDiff(fnd, exp)
-      case _ =>
-        (hl"$fnd", hl"$exp")
+    DiffUtil.mkColoredTypeDiff(fnd, exp) match {
+      case _ if ctx.settings.color.value == "never" => (fnd, exp)
+      case (fnd, exp, change) if change < 0.5 => (fnd, exp)
+      case _ => (fnd, exp)
     }
   }
 }
diff --git a/src/dotty/tools/dotc/util/DiffUtil.scala b/src/dotty/tools/dotc/util/DiffUtil.scala
index 8bb39c88a..b55aee719 100644
--- a/src/dotty/tools/dotc/util/DiffUtil.scala
+++ b/src/dotty/tools/dotc/util/DiffUtil.scala
@@ -32,8 +32,9 @@ object DiffUtil {
     }
 
 
-  /** @return a tuple of the (found, expected) diffs as strings */
-  def mkColoredTypeDiff(found: String, expected: String): (String, String) = {
+  /** @return a tuple of the (found, expected, changedPercentage) diffs as strings */
+  def mkColoredTypeDiff(found: String, expected: String): (String, String, Double) = {
+    var totalChange = 0
     val foundTokens   = splitTokens(found, Nil).toArray
     val expectedTokens = splitTokens(expected, Nil).toArray
 
@@ -42,15 +43,19 @@ object DiffUtil {
 
     val exp = diffExp.collect {
       case Unmodified(str) => str
-      case Inserted(str) => ADDITION_COLOR + str + ANSI_DEFAULT
+      case Inserted(str) =>
+        totalChange += str.length
+        ADDITION_COLOR + str + ANSI_DEFAULT
     }.mkString
 
     val fnd = diffAct.collect {
       case Unmodified(str) => str
-      case Inserted(str) => DELETION_COLOR + str + ANSI_DEFAULT
+      case Inserted(str) =>
+        totalChange += str.length
+        DELETION_COLOR + str + ANSI_DEFAULT
     }.mkString
 
-    (fnd, exp)
+    (fnd, exp, totalChange.toDouble / (expected.length + found.length))
   }
 
   def mkColoredCodeDiff(code: String, lastCode: String, printDiffDel: Boolean): String = {