Fix #1540: overloaded get and isDefined in option-less patmat

src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -240,17 +240,21 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {
           val isDefined = extractorMemberType(prev.tpe, nme.isDefined)
 
           if ((isDefined isRef defn.BooleanClass) && getTp.exists) {
-            val tmpSym = freshSym(prev.pos, prev.tpe, "o")
-            val prevValue = ref(tmpSym).select("get".toTermName).ensureApplied
+            // isDefined and get maybe overloaded
+            val getDenot = prev.tpe.member(nme.get).suchThat(_.info.isParameterless)
+            val isDefinedDenot = prev.tpe.member(nme.isDefined).suchThat(_.info.isParameterless)
 
-              Block(
-                List(ValDef(tmpSym, prev)),
-                // must be isEmpty and get as we don't control the target of the call (prev is an extractor call)
-                ifThenElseZero(
-                  ref(tmpSym).select(nme.isDefined),
-                  Block(List(ValDef(b.asTerm, prevValue)), next)
-                )
+            val tmpSym = freshSym(prev.pos, prev.tpe, "o")
+            val prevValue = ref(tmpSym).select(getDenot.symbol).ensureApplied
+
+            Block(
+              List(ValDef(tmpSym, prev)),
+              // must be isEmpty and get as we don't control the target of the call (prev is an extractor call)
+              ifThenElseZero(
+                ref(tmpSym).select(isDefinedDenot.symbol),
+                Block(List(ValDef(b.asTerm, prevValue)), next)
               )
+            )
           } else {
             assert(defn.isProductSubType(prev.tpe))
             val nullCheck: Tree = prev.select(defn.Object_ne).appliedTo(Literal(Constant(null)))

tests/pos/i1540.scala

@@ -0,0 +1,14 @@
+class Casey1(val a: Int) {
+  def isDefined: Boolean = true
+  def isDefined(x: Int): Boolean = ???
+  def get: Int = a
+  def get(x: Int): String = ???
+}
+object Casey1 { def unapply(a: Casey1) = a }
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val c @ Casey1(x) = new Casey1(0)
+    assert(x == c.get)
+  }
+}