Drop Scala 2.11.x

.travis.yml

@@ -4,12 +4,6 @@ language: scala
 
 matrix:
   include:
-    - jdk: openjdk8
-      scala: 2.11.12
-      env: COVERAGE=coverage
-    - jdk: openjdk11
-      scala: 2.11.12
-      env: COVERAGE=
     - jdk: openjdk8
       scala: 2.13.0
       env: COVERAGE=

README.md

@@ -27,7 +27,7 @@ Cats Effect relies on improved type inference and needs partial unification enab
 
 If your project uses Scala.js, replace the double-`%` with a triple. Note that **cats-effect** has an upstream dependency on **cats-core** version 2.x.
 
-Cross-builds are available for Scala 2.11.x, 2.12.x, and 2.13.0, as well as Scala.js 0.6.x.
+Cross-builds are available for Scala 2.12.x and 2.13.x, as well as Scala.js 0.6.x.
 
 The most current snapshot (or major release) can be found in the maven badge at the top of this readme. If you are a very brave sort, you are free to depend on snapshots; they are stable versions, as they are derived from the git hash rather than an unstable `-SNAPSHOT` suffix, but they do not come with any particular confidence or compatibility guarantees.
 

build.sbt

@@ -151,10 +151,9 @@ val commonSettings = Seq(
 val mimaSettings = Seq(
   mimaPreviousArtifacts := {
     CrossVersion.partialVersion(scalaVersion.value) match {
-      //2.11 has some incompatibilities in core in 2.0.0, 2.13 didn't have a release before
-      case Some((2, 11) | (2, 13)) => Set(organization.value %% name.value % "2.0.0")
-      case Some((2, 12))           => Set(organization.value %% name.value % "1.0.0")
-      case _                       => Set.empty
+      case Some((2, 13)) => Set(organization.value %% name.value % "2.0.0")
+      case Some((2, 12)) => Set(organization.value %% name.value % "1.0.0")
+      case _             => Set.empty
     }
   },
   mimaBinaryIssueFilters ++= {

core/shared/src/main/scala/cats/effect/package.scala

@@ -41,6 +41,7 @@ package object effect {
    * Provides missing methods on Scala 2.11's Either while allowing
    * -Xfatal-warnings along with -Ywarn-unused-import
    */
+  @deprecated("Cats-effect no longer supports Scala 2.11.x", "2.1.0")
   implicit private[effect] class scala211EitherSyntax[A, B](val self: Either[A, B]) extends AnyVal {
     def map[B2](f: B => B2): Either[A, B2] = self match {
       case l @ Left(_) => l.asInstanceOf[Either[A, B2]]

versioning.md

@@ -22,8 +22,6 @@ Within a single *major/minor* version (e.g. the **1.0** in **1.0.5**), all relea
 
 *Backward binary compatibility* is not guaranteed. Thus, code compiled against 1.0.5 may not run with the same semantics against 1.0, though it is *very* likely that it will.
 
-Please note that there are some limits in Scala's binary compatibility story prior to Scala 2.12. At the present time, the guarantees in this section hold for all cats-effect cross-builds: 2.11 and 2.12; but we reserve the right to restrict certain guarantees to just 2.12 in the future.
-
 ## Snapshots
 
 Snapshots may be published to sonatype at any time. They will be denoted as versions of the form `major.minor-hash`, where the `hash` is the 7 character git hash prefix of the commit from which the snapshot was published. Thus, "snapshots" are in fact stable, and can be used as repeatable upstream dependencies if you're feeling courageous. A snapshot with a `major` version of *x* and a `minor` version of *y* is expected (and indeed, machine-checked in so far as possible) to be binary compatible with the full release with version *x*.*y* (and all its subsequent minor versions). Thus, eviction works basically the way you expect. The only exception to this is *unreleased* incompatible versions, since such versions are still in flux and early snapshots may be incompatible with this future release.