Keep track of extension method rhs in Mode

Author: odersky

compiler/src/dotty/tools/dotc/core/Mode.scala

@@ -112,4 +112,7 @@ object Mode {
 
   /** Are we in a quote in a pattern? */
   val QuotedPattern: Mode = newMode(25, "QuotedPattern")
+
+  /** Are we typechecking the rhs of an extension method? */
+  val InExtensionMethod: Mode = newMode(26, "InExtensionMethod")
 }

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -1353,7 +1353,8 @@ class Namer { typer: Typer =>
       def dealiasIfUnit(tp: Type) = if (tp.isRef(defn.UnitClass)) defn.UnitType else tp
 
       var rhsCtx = ctx.fresh.addMode(Mode.InferringReturnType)
-      if (sym.isInlineMethod) rhsCtx = rhsCtx.addMode(Mode.InlineableBody)
+      if sym.isInlineMethod then rhsCtx = rhsCtx.addMode(Mode.InlineableBody)
+      if sym.is(ExtensionMethod) then rhsCtx = rhsCtx.addMode(Mode.InExtensionMethod)
       if (typeParams.nonEmpty) {
         // we'll be typing an expression from a polymorphic definition's body,
         // so we must allow constraining its type parameters

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1977,7 +1977,8 @@ class Typer extends Namer
       }
     }
 
-    if (sym.isInlineMethod) rhsCtx.addMode(Mode.InlineableBody)
+    if sym.isInlineMethod then rhsCtx.addMode(Mode.InlineableBody)
+    if sym.is(ExtensionMethod) then rhsCtx.addMode(Mode.InExtensionMethod)
     val rhs1 = PrepareInlineable.dropInlineIfError(sym,
       if sym.isScala2Macro then typedScala2MacroBody(ddef.rhs)(using rhsCtx)
       else typedExpr(ddef.rhs, tpt1.tpe.widenExpr)(using rhsCtx))