Refactor the abstract domain of global init checker to compile http4s (#22179)

This is a draft PR that contains fixes to the initialization checker, so
that it can successfully check http4s in community-build

[test_scala2_library_tasty]

Author: olhotak

Diff for: compiler/src/dotty/tools/dotc/transform/init/Objects.scala

@@ -1,9 +1,6 @@
 ## See #18882
 patmat.scala
 t9312.scala
-unapplySeq-implicit-arg.scala
-unapplySeq-implicit-arg2.scala
-unapplySeq-implicit-arg3.scala
 ScalaCheck.scala
 mutable-read8.scala
 TypeCast.scala

Diff for: compiler/test/dotc/neg-init-global-scala2-library-tasty.excludelist

@@ -233,6 +233,10 @@ class CompilationTests {
     implicit val testGroup: TestGroup = TestGroup("checkInitGlobal")
     compileFilesInDir("tests/init-global/warn", defaultOptions.and("-Ysafe-init-global"), FileFilter.exclude(TestSources.negInitGlobalScala2LibraryTastyExcludelisted)).checkWarnings()
     compileFilesInDir("tests/init-global/pos", defaultOptions.and("-Ysafe-init-global", "-Xfatal-warnings"), FileFilter.exclude(TestSources.posInitGlobalScala2LibraryTastyExcludelisted)).checkCompile()
+    if Properties.usingScalaLibraryTasty && !Properties.usingScalaLibraryCCTasty then
+      compileFilesInDir("tests/init-global/warn-tasty", defaultOptions.and("-Ysafe-init-global"), FileFilter.exclude(TestSources.negInitGlobalScala2LibraryTastyExcludelisted)).checkWarnings()
+      compileFilesInDir("tests/init-global/pos-tasty", defaultOptions.and("-Ysafe-init-global", "-Xfatal-warnings"), FileFilter.exclude(TestSources.posInitGlobalScala2LibraryTastyExcludelisted)).checkCompile()
+    end if
   }
 
   // initialization tests

Diff for: compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -0,0 +1,5 @@
+object A:
+  val a = f(10)
+  val b = -a
+  val c = b.toDouble
+  def f(x: Int) = x * 2 + 5

Diff for: tests/init-global/pos/array-size-zero.scala renamed to tests/init-global/pos-tasty/array-size-zero.scala

@@ -0,0 +1,16 @@
+package p
+package object a {
+  val b = 10
+  implicit class CI(s: StringContext) {
+    def ci(args: Any*) = 10
+  }
+}
+
+import p.a._
+
+object A:
+  val f = b // p.a(ObjectRef(p.a)).b
+  def foo(s: String): String = s
+  val f1 = ci"a" // => p.a(Package(p).select(a)).CI(StringContext"a").ci()
+
+

Diff for: tests/init-global/pos/arithmetic.scala

@@ -1,4 +1,4 @@
--- Warning: tests/init-global/warn/unapplySeq-implicit-arg.scala:11:20 -------------------------------------------------
+-- Warning: tests/init-global/warn-tasty/unapplySeq-implicit-arg.scala:11:20 -------------------------------------------
 11 |  val i2: Int = Seq(i2) match // warn
    |                    ^^
    |                    Access uninitialized field value i2. Calling trace:

Diff for: tests/init-global/pos/packageObjectStringInterpolator.scala

@@ -1,4 +1,4 @@
--- Warning: tests/init-global/warn/unapplySeq-implicit-arg2.scala:4:9 --------------------------------------------------
+-- Warning: tests/init-global/warn-tasty/unapplySeq-implicit-arg2.scala:4:9 --------------------------------------------
 4 |    Some(i1 +: seqi) // warn
   |         ^^
   |Access uninitialized field value i1. Calling trace:

Diff for: tests/init-global/warn/patmat.check renamed to tests/init-global/warn-tasty/patmat.check

@@ -1,4 +1,4 @@
--- Warning: tests/init-global/warn/unapplySeq-implicit-arg3.scala:3:27 -------------------------------------------------
+-- Warning: tests/init-global/warn-tasty/unapplySeq-implicit-arg3.scala:3:27 -------------------------------------------
 3 |    def m(seq: Seq[Int]) = i1 +: seq // warn
   |                           ^^
   |Access uninitialized field value i1. Calling trace:

Diff for: tests/init-global/warn/patmat.scala renamed to tests/init-global/warn-tasty/patmat.scala

@@ -1,11 +1,11 @@
--- Warning: tests/init-global/warn/mutable-array.scala:8:19 ------------------------------------------------------------
-8 |  val x: Int = box.value // warn
+-- Warning: tests/init-global/warn/mutable-array.scala:9:19 ------------------------------------------------------------
+9 |  val x: Int = box.value // warn
   |               ^^^^^^^^^
   |Reading mutable state of object A during initialization of object B.
   |Reading mutable state of other static objects is forbidden as it breaks initialization-time irrelevance. Calling trace:
   |├── object B:	[ mutable-array.scala:5 ]
   |│   ^
-  |└── val x: Int = box.value // warn	[ mutable-array.scala:8 ]
+  |└── val x: Int = box.value // warn	[ mutable-array.scala:9 ]
   |                 ^^^^^^^^^
   |The mutable state is created through: 
   |├── object A:	[ mutable-array.scala:1 ]

Diff for: tests/init-global/warn/unapplySeq-implicit-arg.check renamed to tests/init-global/warn-tasty/unapplySeq-implicit-arg.check

@@ -3,6 +3,7 @@ object A:
   val box: Box = new Box(0)
 
 object B:
-  val boxes: Array[A.Box] = Array(A.box)
+  val boxes = new Array[A.Box](2)
+  boxes(0) = A.box
   val box: A.Box = boxes(0)
   val x: Int = box.value // warn

Diff for: tests/init-global/warn/unapplySeq-implicit-arg.scala renamed to tests/init-global/warn-tasty/unapplySeq-implicit-arg.scala

@@ -0,0 +1,20 @@
+-- Warning: tests/init-global/warn/widen.scala:13:13 -------------------------------------------------------------------
+13 |        t.foo() // warn
+   |        ^^^^^^^
+   |        Value is unknown to the checker due to widening. Calling trace:
+   |        ├── object O:	[ widen.scala:9 ]
+   |        │   ^
+   |        ├── val a = bar(new C)	[ widen.scala:20 ]
+   |        │           ^^^^^^^^^^
+   |        ├── def bar(t: T) = {	[ widen.scala:10 ]
+   |        │   ^
+   |        ├── new A	[ widen.scala:18 ]
+   |        │   ^^^^^
+   |        ├── class A {	[ widen.scala:11 ]
+   |        │   ^
+   |        ├── val b = new B	[ widen.scala:16 ]
+   |        │           ^^^^^
+   |        ├── class B {	[ widen.scala:12 ]
+   |        │   ^
+   |        └── t.foo() // warn	[ widen.scala:13 ]
+   |            ^^^^^^^

Diff for: tests/init-global/warn/unapplySeq-implicit-arg2.check renamed to tests/init-global/warn-tasty/unapplySeq-implicit-arg2.check

@@ -0,0 +1,20 @@
+trait T {
+  def foo(): Unit
+}
+
+class C extends T {
+  def foo(): Unit = println("Calling foo on an instance of C!")
+}
+
+object O:
+  def bar(t: T) = {
+    class A {
+      class B {
+        t.foo() // warn
+      }
+
+      val b = new B
+    }
+    new A
+  }
+  val a = bar(new C)