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author | Jason Zaugg <jzaugg@gmail.com> | 2014-11-06 13:12:19 +1000 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2014-11-06 14:28:29 +1000 |
commit | d6d8c06e02fa1e93e5dd37eeb08b2c1bb3805dd8 (patch) | |
tree | 7822cc48706c201d5b0cdb23d6e583534bb7847c /src | |
parent | cd50464cd019bc6a489a72b98293c30b91352bab (diff) | |
download | scala-d6d8c06e02fa1e93e5dd37eeb08b2c1bb3805dd8.tar.gz scala-d6d8c06e02fa1e93e5dd37eeb08b2c1bb3805dd8.tar.bz2 scala-d6d8c06e02fa1e93e5dd37eeb08b2c1bb3805dd8.zip |
SI-8962 Fix regression with skolems in pattern translation
During the refactoring of error reporting in 258d95c7b15, the result
of `Context#reportError` was changed once we had switched to
using a `ThrowingReporter`, which is still the case in post
typer phase typechecking
This was enough to provoke a type error in the enclosed test.
Here's a diff of the typer log:
% scalac-hash 258d95~1 -Ytyper-debug sandbox/test.scala 2>&1 | tee sandbox/good.log
% scalac-hash 258d95 -Ytyper-debug sandbox/test.scala 2>&1 | tee sandbox/bad.log
% diff -U100 sandbox/{good,bad}.log | gist --filename=SI-8962-typer-log.diff
https://gist.github.com/retronym/3ccbe7e0791447d272a6
The test `Context#reportError` happens to be used when deciding
whether the type checker should be lenient when it hits a type error.
In lenient mode (see `adaptMismatchedSkolems`), it `adapt` retries
with after slackening the expected type by replacing GADT and
existential skolems with wildcard types. This is to accomodate
known type-incorrect trees generated by the pattern matcher.
This commit restores the old semantics of `reportError`, which means
it is `false` when a `ThrowingReporter` is being used.
For those still reading, here's some more details.
The trees of the `run2` example from the enclosed test. Notice that
after typechecking, `expr` has a type containing GADT skolems. The
pattern matcher assumes that calling the case field accessor `expr`
on the temporary val `x2 : Let[A with A]` containing the scrutinee
will result in a compatible expression, however this it does not.
Perhaps the pattern matcher should generate casts, rather than
relying on the typer to turn a blind eye.
```
[[syntax trees at end of typer]] // t8962b.scala
...
def run2[A](nc: Outer2[A,A]): Outer2[Inner2[A],A] = nc match {
case (expr: Outer2[Inner2[?A2 with ?A1],?A2 with ?A1])Let2[A with A]((expr @ _{Outer2[Inner2[?A2 with ?A1],?A2 with ?A1]}){Outer2[Inner2[?A2 with ?A1],?A2 with ?A1]}){Let2[A with A]} =>
(expr{Outer2[Inner2[?A2 with ?A1],?A2 with ?A1]}: Outer2[Inner2[A],A]){Outer2[Inner2[A],A]}
}{Outer2[Inner2[A],A]}
[[syntax trees at end of patmat]] // t8962b.scala
def run2[A](nc: Outer2[A,A]): Outer2[Inner2[A],A] = {
case <synthetic> val x1: Outer2[A,A] = nc{Outer2[A,A]};
case5(){
if (x1.isInstanceOf[Let2[A with A]])
{
<synthetic> val x2: Let2[A with A] = (x1.asInstanceOf[Let2[A with A]]: Let2[A with A]){Let2[A with A]};
{
val expr: Outer2[Inner2[?A2 with ?A1],?A2 with ?A1] = x2.expr{<null>};
matchEnd4{<null>}((expr{Outer2[Inner2[?A2 with ?A1],?A2 with ?A1]}: Outer2[Inner2[A],A]){Outer2[Inner2[A],A]}){<null>}
...
```
Diffstat (limited to 'src')
-rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Contexts.scala | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala index eb29ccf4e1..e278130437 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala @@ -330,7 +330,7 @@ trait Contexts { self: Analyzer => // if set, errors will not be reporter/thrown def bufferErrors = reporter.isBuffering - def reportErrors = !bufferErrors + def reportErrors = !(bufferErrors || reporter.isThrowing) // whether to *report* (which is separate from buffering/throwing) ambiguity errors def ambiguousErrors = this(AmbiguousErrors) @@ -1247,6 +1247,7 @@ trait Contexts { self: Analyzer => def makeImmediate: ContextReporter = this def makeBuffering: ContextReporter = this def isBuffering: Boolean = false + def isThrowing: Boolean = false /** Emit an ambiguous error according to context.ambiguousErrors * @@ -1384,6 +1385,7 @@ trait Contexts { self: Analyzer => * TODO: get rid of it, use ImmediateReporter and a check for reporter.hasErrors where necessary */ private[typechecker] class ThrowingReporter extends ContextReporter { + override def isThrowing = true protected def handleError(pos: Position, msg: String): Unit = throw new TypeError(pos, msg) } |