diff options
Diffstat (limited to 'compiler/src/dotty/tools/dotc/typer/Applications.scala')
| -rw-r--r-- | compiler/src/dotty/tools/dotc/typer/Applications.scala | 35 |
1 files changed, 32 insertions, 3 deletions
diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala index 6c398cd72..11121e1f3 100644 --- a/compiler/src/dotty/tools/dotc/typer/Applications.scala +++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala @@ -250,8 +250,37 @@ trait Applications extends Compatibility { self: Typer with Dynamic => /** Splice new method reference into existing application */ def spliceMeth(meth: Tree, app: Tree): Tree = app match { - case Apply(fn, args) => Apply(spliceMeth(meth, fn), args) - case TypeApply(fn, targs) => TypeApply(spliceMeth(meth, fn), targs) + case Apply(fn, args) => + spliceMeth(meth, fn).appliedToArgs(args) + case TypeApply(fn, targs) => + // Note: It is important that the type arguments `targs` are passed in new trees + // instead of being spliced in literally. Otherwise, a type argument to a default + // method could be constructed as the definition site of the type variable for + // that default constructor. This would interpolate type variables too early, + // causing lots of tests (among them tasty_unpickleScala2) to fail. + // + // The test case is in i1757.scala. Here we have a variable `s` and a method `cpy` + // defined like this: + // + // var s + // def cpy[X](b: List[Int] = b): B[X] = new B[X](b) + // + // The call `s.cpy()` then gets expanded to + // + // { val $1$: B[Int] = this.s + // $1$.cpy[X']($1$.cpy$default$1[X'] + // } + // + // A type variable gets interpolated if it does not appear in the type + // of the current tree and the current tree contains the variable's "definition". + // Previously, the polymorphic function tree to which the variable was first added + // was taken as the variable's definition. But that fails here because that + // tree was `s.cpy` but got transformed into `$1$.cpy`. We now take the type argument + // [X'] of the variable as its definition tree, which is more robust. But then + // it's crucial that the type tree is not copied directly as argument to + // `cpy$default$1`. If it was, the variable `X'` would already be interpolated + // when typing the default argument, which is too early. + spliceMeth(meth, fn).appliedToTypes(targs.tpes) case _ => meth } @@ -333,7 +362,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic => val getter = findDefaultGetter(n + numArgs(normalizedFun)) if (getter.isEmpty) missingArg(n) else { - addTyped(treeToArg(spliceMeth(getter withPos appPos, normalizedFun)), formal) + addTyped(treeToArg(spliceMeth(getter withPos normalizedFun.pos, normalizedFun)), formal) matchArgs(args1, formals1, n + 1) } } |