Add checks for the consistency of the parents in TreeChecker

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

@@ -2,6 +2,7 @@ package dotty.tools
 package dotc
 package transform
 
+import ast.Trees
 import core.Phases.*
 import core.DenotTransformers.*
 import core.Denotations.*
@@ -1044,7 +1045,20 @@ object Erasure {
 
     override def typedClassDef(cdef: untpd.TypeDef, cls: ClassSymbol)(using Context): Tree =
       if cls.is(Flags.Erased) then erasedDef(cls)
-      else super.typedClassDef(cdef, cls)
+      else
+        val typedTree@TypeDef(name, impl @ Template(constr, _, self, _)) = super.typedClassDef(cdef, cls): @unchecked
+        // In the case where a trait extends a class, we need to strip any non trait class from the signature
+        // and accept the first one (see tests/run/mixins.scala)
+        val newTraits = impl.parents.tail.filterConserve: tree =>
+          def isTraitConstructor = tree match
+            case Trees.Block(_, expr) => // Specific management for trait constructors (see tests/pos/i9213.scala)
+              expr.symbol.isConstructor && expr.symbol.owner.is(Flags.Trait)
+            case _ => tree.symbol.isConstructor && tree.symbol.owner.is(Flags.Trait)
+          tree.symbol.is(Flags.Trait) || isTraitConstructor
+
+        val newParents = if impl.parents.tail eq newTraits then impl.parents
+                         else impl.parents.head :: newTraits
+        cpy.TypeDef(typedTree)(rhs = cpy.Template(impl)(parents = newParents))
 
     override def typedAnnotated(tree: untpd.Annotated, pt: Type)(using Context): Tree =
       typed(tree.arg, pt)

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

@@ -547,8 +547,24 @@ object TreeChecker {
         i"owner chain = ${tree.symbol.ownersIterator.toList}%, %, ctxOwners = ${ctx.outersIterator.map(_.owner).toList}%, %")
     }
 
+    private def checkParents(tree: untpd.TypeDef)(using Context): Unit = {
+      val TypeDef(_, impl: Template) = tree: @unchecked
+      assert(ctx.owner.isClass)
+      val sym = ctx.owner.asClass
+      if !sym.isPrimitiveValueClass then
+        val symbolParents = sym.classInfo.parents.map(_.dealias.typeSymbol)
+        val treeParents = impl.parents.map(_.tpe.dealias.typeSymbol)
+        assert(symbolParents == treeParents,
+        i"""Parents of class symbol differs from the parents in the tree for $sym
+            |
+            |Parents in symbol: $symbolParents
+            |Parents in tree: $treeParents
+            |""".stripMargin)
+    }
+
     override def typedTypeDef(tdef: untpd.TypeDef, sym: Symbol)(using Context): Tree = {
       assert(sym.info.isInstanceOf[ClassInfo | TypeBounds], i"wrong type, expect a template or type bounds for ${sym.fullName}, but found: ${sym.info}")
+      if sym.isClass then checkParents(tdef)
       super.typedTypeDef(tdef, sym)
     }
 
@@ -561,6 +577,8 @@ object TreeChecker {
       checkOwner(impl)
       checkOwner(impl.constr)
 
+      checkParents(cdef)
+
       def isNonMagicalMember(x: Symbol) =
         !x.isValueClassConvertMethod &&
         !x.name.is(DocArtifactName) &&
@@ -812,7 +830,7 @@ object TreeChecker {
             else err.getStackTrace.nn.mkString("  ", "  \n", "")
 
           report.error(
-            s"""Malformed tree was found while expanding macro with -Xcheck-macros.
+            em"""Malformed tree was found while expanding macro with -Xcheck-macros.
                |The tree does not conform to the compiler's tree invariants.
                |
                |Macro was:

tests/neg-macros/i18677-a.check

@@ -0,0 +1,22 @@
+
+-- Error: tests/neg-macros/i18677-a/Test_2.scala:4:6 -------------------------------------------------------------------
+3 |@extendFoo
+4 |class AFoo // error
+  |^
+  |Malformed tree was found while expanding macro with -Xcheck-macros.
+  |The tree does not conform to the compiler's tree invariants.
+  |
+  |Macro was:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/i18677-a/Test_2.scala") @extendFoo class AFoo()
+  |
+  |The macro returned:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/i18677-a/Test_2.scala") @extendFoo class AFoo() extends Foo
+  |
+  |Error:
+  |assertion failed: Parents of class symbol differs from the parents in the tree for class AFoo
+  |
+  |Parents in symbol: [class Object]
+  |Parents in tree: [trait Foo]
+  |
+  |
+  |stacktrace available when compiling with `-Ydebug`

tests/neg-macros/i18677-a/Macro_1.scala

@@ -0,0 +1,18 @@
+//> using -expermiental
+
+import annotation.MacroAnnotation
+import quoted.*
+
+trait Foo
+
+class extendFoo extends MacroAnnotation :
+    override def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] =
+        import quotes.reflect.*
+        tree match
+            case ClassDef(name, ctr, p, self, body) =>
+                val parents = List(TypeTree.of[Foo])
+                val newTree = ClassDef.copy(tree)(name, ctr,  parents, self, body)
+                newTree :: Nil
+            case _ =>
+                report.error("@extendFoo can only annotate class definitions")
+                tree :: Nil

tests/neg-macros/i18677-a/Test_2.scala

@@ -0,0 +1,4 @@
+//> using -expermiental
+
+@extendFoo
+class AFoo // error

tests/neg-macros/i18677-b.check

@@ -0,0 +1,22 @@
+
+-- Error: tests/neg-macros/i18677-b/Test_2.scala:4:6 -------------------------------------------------------------------
+3 |@extendFoo
+4 |class AFoo // error
+  |^
+  |Malformed tree was found while expanding macro with -Xcheck-macros.
+  |The tree does not conform to the compiler's tree invariants.
+  |
+  |Macro was:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/i18677-b/Test_2.scala") @extendFoo class AFoo()
+  |
+  |The macro returned:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/i18677-b/Test_2.scala") @extendFoo class AFoo() extends Foo
+  |
+  |Error:
+  |assertion failed: Parents of class symbol differs from the parents in the tree for class AFoo
+  |
+  |Parents in symbol: [class Object]
+  |Parents in tree: [class Foo]
+  |
+  |
+  |stacktrace available when compiling with `-Ydebug`

tests/neg-macros/i18677-b/Macro_1.scala

@@ -0,0 +1,18 @@
+//> using -expermiental
+
+import annotation.MacroAnnotation
+import quoted.*
+
+class Foo
+
+class extendFoo extends MacroAnnotation :
+    override def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] =
+        import quotes.reflect.*
+        tree match
+            case ClassDef(name, ctr, p, self, body) =>
+                val parents = List(TypeTree.of[Foo])
+                val newTree = ClassDef.copy(tree)(name, ctr,  parents, self, body)
+                newTree :: Nil
+            case _ =>
+                report.error("@extendFoo can only annotate class definitions")
+                tree :: Nil

tests/neg-macros/i18677-b/Test_2.scala

@@ -0,0 +1,4 @@
+//> using -expermiental
+
+@extendFoo
+class AFoo // error

tests/neg-macros/wrong-owner.check

@@ -5,19 +5,18 @@
 5 |class Foo // error
   |^
   |Malformed tree was found while expanding macro with -Xcheck-macros.
-  |               |The tree does not conform to the compiler's tree invariants.
-  |               |
-  |               |Macro was:
-  |               |@scala.annotation.internal.SourceFile("tests/neg-macros/wrong-owner/Test_2.scala") @wrongOwner @scala.annotation.experimental class Foo()
-  |               |
-  |               |The macro returned:
-  |               |@scala.annotation.internal.SourceFile("tests/neg-macros/wrong-owner/Test_2.scala") @wrongOwner @scala.annotation.experimental class Foo() {
+  |The tree does not conform to the compiler's tree invariants.
+  |
+  |Macro was:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/wrong-owner/Test_2.scala") @wrongOwner @scala.annotation.experimental class Foo()
+  |
+  |The macro returned:
+  |@scala.annotation.internal.SourceFile("tests/neg-macros/wrong-owner/Test_2.scala") @wrongOwner @scala.annotation.experimental class Foo() {
   |  override def toString(): java.lang.String = "Hello from macro"
   |}
-  |               |
-  |               |Error:
-  |               |assertion failed: bad owner; method toString has owner class String, expected was class Foo
+  |
+  |Error:
+  |assertion failed: bad owner; method toString has owner class String, expected was class Foo
   |owner chain = method toString, class String, package java.lang, package java, package <root>, ctxOwners = class Foo, class Foo, package <empty>, package <empty>, package <empty>, package <root>, package <root>, package <root>, package <root>, package <root>, package <root>, <none>, <none>, <none>, <none>, <none>
-  |               |
+  |
   |stacktrace available when compiling with `-Ydebug`
-  |               |