Fix fresh exhaustivity warnings in the compiler

Author: dwijnand

compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala

@@ -169,7 +169,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
 
     /* ---------------- helper utils for generating classes and fields ---------------- */
 
-    def genPlainClass(cd0: TypeDef) = cd0 match {
+    def genPlainClass(cd0: TypeDef) = (cd0: @unchecked) match {
       case TypeDef(_, impl: Template) =>
       assert(cnode == null, "GenBCode detected nested methods.")
 

compiler/src/dotty/tools/dotc/core/Comments.scala

@@ -405,15 +405,10 @@ object Comments {
       val Trim = "(?s)^[\\s&&[^\n\r]]*(.*?)\\s*$".r
 
       val raw = ctx.docCtx.flatMap(_.docstring(sym).map(_.raw)).getOrElse("")
-      defs(sym) ++= defines(raw).map {
-        str => {
-          val start = skipWhitespace(str, "@define".length)
-          val (key, value) = str.splitAt(skipVariable(str, start))
-          key.drop(start) -> value
-        }
-      } map {
-        case (key, Trim(value)) =>
-          variableName(key) -> value.replaceAll("\\s+\\*+$", "")
+      defs(sym) ++= defines(raw).map { str =>
+        val start = skipWhitespace(str, "@define".length)
+        val (key, Trim(value)) = str.splitAt(skipVariable(str, start)): @unchecked
+        variableName(key.drop(start)) -> value.replaceAll("\\s+\\*+$", "")
       }
     }
 

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -1383,30 +1383,31 @@ trait Implicits:
             if alt1.isExtension then
               // Fall back: if both results are extension method applications,
               // compare the extension methods instead of their wrappers.
-              def stripExtension(alt: SearchSuccess) = methPart(stripApply(alt.tree)).tpe
-              (stripExtension(alt1), stripExtension(alt2)) match
-                case (ref1: TermRef, ref2: TermRef) =>
-                  // ref1 and ref2 might refer to type variables owned by
-                  // alt1.tstate and alt2.tstate respectively, to compare the
-                  // alternatives correctly we need a TyperState that includes
-                  // constraints from both sides, see
-                  // tests/*/extension-specificity2.scala for test cases.
-                  val constraintsIn1 = alt1.tstate.constraint ne ctx.typerState.constraint
-                  val constraintsIn2 = alt2.tstate.constraint ne ctx.typerState.constraint
-                  def exploreState(alt: SearchSuccess): TyperState =
-                    alt.tstate.fresh(committable = false)
-                  val comparisonState =
-                    if constraintsIn1 && constraintsIn2 then
-                      exploreState(alt1).mergeConstraintWith(alt2.tstate)
-                    else if constraintsIn1 then
-                      exploreState(alt1)
-                    else if constraintsIn2 then
-                      exploreState(alt2)
-                    else
-                      ctx.typerState
-
-                  diff = inContext(searchContext().withTyperState(comparisonState)):
-                    compare(ref1, ref2, preferGeneral = true)
+              def stripExtension(alt: SearchSuccess) =
+                methPart(stripApply(alt.tree)).tpe: @unchecked match { case ref: TermRef => ref }
+              val ref1 = stripExtension(alt1)
+              val ref2 = stripExtension(alt2)
+              // ref1 and ref2 might refer to type variables owned by
+              // alt1.tstate and alt2.tstate respectively, to compare the
+              // alternatives correctly we need a TyperState that includes
+              // constraints from both sides, see
+              // tests/*/extension-specificity2.scala for test cases.
+              val constraintsIn1 = alt1.tstate.constraint ne ctx.typerState.constraint
+              val constraintsIn2 = alt2.tstate.constraint ne ctx.typerState.constraint
+              def exploreState(alt: SearchSuccess): TyperState =
+                alt.tstate.fresh(committable = false)
+              val comparisonState =
+                if constraintsIn1 && constraintsIn2 then
+                  exploreState(alt1).mergeConstraintWith(alt2.tstate)
+                else if constraintsIn1 then
+                  exploreState(alt1)
+                else if constraintsIn2 then
+                  exploreState(alt2)
+                else
+                  ctx.typerState
+
+              diff = inContext(searchContext().withTyperState(comparisonState)):
+                compare(ref1, ref2, preferGeneral = true)
             else // alt1 is a conversion, prefer extension alt2 over it
               diff = -1
           if diff < 0 then alt2