Backport "Consistently use TypeMismatch in TreeChecker" to LTS (#22119)

Backports #21529 to the 3.3.5.

PR submitted by the release tooling.
[skip ci]

Author: WojciechMazur

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -397,19 +397,8 @@ object TreeChecker {
             promote(tree)
           case _ =>
             val tree1 = super.typedUnadapted(tree, pt, locked)
-            def isSubType(tp1: Type, tp2: Type) =
-              (tp1 eq tp2) || // accept NoType / NoType
-              (tp1 <:< tp2)
-            def divergenceMsg(tp1: Type, tp2: Type) =
-              s"""Types differ
-                |Original type : ${tree.typeOpt.show}
-                |After checking: ${tree1.tpe.show}
-                |Original tree : ${tree.show}
-                |After checking: ${tree1.show}
-                |Why different :
-              """.stripMargin + core.TypeComparer.explained(_.isSubType(tp1, tp2))
-            if (tree.hasType) // it might not be typed because Typer sometimes constructs new untyped trees and resubmits them to typedUnadapted
-              assert(isSubType(tree1.tpe, tree.typeOpt), divergenceMsg(tree1.tpe, tree.typeOpt))
+            if tree.hasType then // it might not be typed because Typer sometimes constructs new untyped trees and resubmits them to typedUnadapted
+              checkType(tree1.tpe, tree.typeOpt, tree, "typedUnadapted")
             tree1
         checkNoOrphans(res.tpe)
         phasesToCheck.foreach(_.checkPostCondition(res))
@@ -747,28 +736,25 @@ object TreeChecker {
     override def adapt(tree: Tree, pt: Type, locked: TypeVars)(using Context): Tree = {
       def isPrimaryConstructorReturn =
         ctx.owner.isPrimaryConstructor && pt.isRef(ctx.owner.owner) && tree.tpe.isRef(defn.UnitClass)
-      def infoStr(tp: Type) = tp match {
-        case tp: TypeRef =>
-          val sym = tp.symbol
-          i"${sym.showLocated} with ${tp.designator}, flags = ${sym.flagsString}, underlying = ${tp.underlyingIterator.toList}%, %"
-        case _ =>
-          "??"
-      }
-      if (ctx.mode.isExpr &&
-          !tree.isEmpty &&
-          !isPrimaryConstructorReturn &&
-          !pt.isInstanceOf[FunOrPolyProto])
-        assert(tree.tpe <:< pt, {
-          val mismatch = TypeMismatch(tree.tpe, pt, Some(tree))
-          i"""|${mismatch.msg}
-              |found: ${infoStr(tree.tpe)}
-              |expected: ${infoStr(pt)}
-              |tree = $tree""".stripMargin
-        })
+      if ctx.mode.isExpr
+        && !tree.isEmpty
+        && !isPrimaryConstructorReturn
+        && !pt.isInstanceOf[FunOrPolyProto]
+      then
+        checkType(tree.tpe, pt, tree, "adapt")
       tree
     }
 
     override def simplify(tree: Tree, pt: Type, locked: TypeVars)(using Context): tree.type = tree
+
+    private def checkType(tp1: Type, tp2: Type, tree: untpd.Tree, step: String)(using Context) =
+      // Accept NoType <:< NoType as true
+      assert((tp1 eq tp2) || (tp1 <:< tp2), {
+        val mismatch = TypeMismatch(tp1, tp2, None)
+        i"""|Type Mismatch (while checking $step):
+            |${mismatch.message}${mismatch.explanation}
+            |tree = $tree ${tree.className}""".stripMargin
+      })
   }
 
   /** Tree checker that can be applied to a local tree. */