WIP - Performance improvement to global initialization checker

compiler/src/dotty/tools/dotc/transform/init/Util.scala

@@ -109,8 +109,3 @@ object Util:
 
     // A concrete class may not be instantiated if the self type is not satisfied
     instantiable && cls.enclosingPackageClass != defn.StdLibPatchesPackage.moduleClass
-
-  /** Whether the class or its super class/trait contains any mutable fields? */
-  def isMutable(cls: ClassSymbol)(using Context): Boolean =
-    cls.classInfo.decls.exists(_.is(Flags.Mutable)) ||
-    cls.parentSyms.exists(parentCls => isMutable(parentCls.asClass))

tests/init-global/pos/footprint-2nd-ctor.scala

@@ -0,0 +1,17 @@
+class Box[T](var value: T)
+
+class A:
+  var box = new Box[Int](10)
+
+  def update(n: Int) =
+    box.value = n
+
+  def this(n: Int) =
+    this()
+    box.value = n
+
+class B(n: Int) extends A(n):
+  this.update(n * n)
+
+object A:
+  val a = new B(20)

tests/init-global/pos/footprint-local.scala

@@ -0,0 +1,6 @@
+object A:
+  val f = foo()
+  val a = f()
+  def foo(): () => Int =
+    var x = 10
+    () => x

tests/init-global/pos/footprint.scala

@@ -0,0 +1,15 @@
+class Box(var x: String)
+
+object A:
+  val a = new Box("a")
+  val c = foo()
+  def foo(): Box = C.c
+
+object B:
+  val b = new Box("b")
+  val a = bar()
+
+  def bar(): Box = A.a
+
+object C:
+  val c = new Box("c")

tests/init-global/pos/footprint2.scala

@@ -0,0 +1,26 @@
+class BreakControl extends Throwable
+
+object Breaks:
+  private val breakException = new BreakControl
+
+  def breakable(op: => Unit): Unit =
+    try op catch { case ex: BreakControl if ex eq breakException => }
+
+  def break(): Nothing = throw breakException
+
+object A:
+  val n = foo("hello")
+  def foo(s: String): Int =
+    val len = s.length
+    var i = 0
+
+    while (i < len) {
+      Breaks.breakable {
+        val c = s.charAt(i)
+
+        if c == '\n' then Breaks.break()
+      }
+      i += 1
+    }
+
+    i

tests/init-global/pos/sconfig-array.scala

@@ -0,0 +1,26 @@
+import java.{lang => jl}
+
+final class ConfigValueType private (val name: String, val ordinal: Int)
+
+object ConfigValueType:
+  final val OBJECT = new ConfigValueType("OBJECT", 0)
+  final val LIST = new ConfigValueType("LIST", 1)
+  final val NUMBER = new ConfigValueType("NUMBER", 2)
+  final val BOOLEAN = new ConfigValueType("BOOLEAN", 3)
+  final val NULL = new ConfigValueType("NULL", 4)
+  final val STRING = new ConfigValueType("STRING", 5)
+
+  final val _values: Array[ConfigValueType] =
+    Array(OBJECT, LIST, NUMBER, BOOLEAN, NULL, STRING)
+
+  def values: Array[ConfigValueType] = _values.clone()
+
+  def valueOf(name: String): ConfigValueType =
+    _values.find(_.name == name).getOrElse {
+      throw new IllegalArgumentException(
+        "No enum const ConfigValueType." + name
+      )
+    }
+
+object Usage:
+  val c = ConfigValueType.valueOf("LIST")

tests/init-global/pos/sconfig.scala

@@ -0,0 +1,89 @@
+abstract class B
+
+class C(var o: () => B | Int) extends B
+
+class D(var o: () => B | Int) extends B
+
+object A:
+  def f1(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f2(c, i + 1)
+    c = f1(c, i + 1)
+    c
+
+  def f2(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f3(c, i + 1)
+    c
+
+  def f3(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f4(c, i + 1)
+    c
+
+  def f4(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f5(c, i + 1)
+    c
+
+  def f5(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f6(c, i + 1)
+    c
+
+  def f6(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f7(c, i + 1)
+    c
+
+  def f7(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f8(c, i + 1)
+    c
+
+  def f8(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f9(c, i + 1)
+    c
+
+  def f9(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f10(c, i + 1)
+    c
+
+  def f10(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f11(c, i + 1)
+    c
+
+  def f11(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f12(c, i + 1)
+    c
+
+  def f12(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f13(c, i + 1)
+    c
+
+  def f13(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f14(c, i + 1) // non-termination if use f1
+    c
+
+  def f14(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f15(c, i + 1)
+    c
+
+  def f15(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f16(c, i + 1)
+    c
+
+  def f16(a: () => B, i: Int): () => B =
+    var c = () => if i % 2 == 0 then new C(a) else new D(a)
+    c = f1(c, i + 1)
+    c
+
+  val c = f1(() => new C(() => 3), 10)