Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix widening logic to keep instantiation within bounds #16417

Merged
merged 1 commit into from
Nov 28, 2022
Merged

Fix widening logic to keep instantiation within bounds #16417

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 5 additions & 8 deletions compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -624,8 +624,9 @@ trait ConstraintHandling {

/** Widen inferred type `inst` with upper `bound`, according to the following rules:
* 1. If `inst` is a singleton type, or a union containing some singleton types,
* widen (all) the singleton type(s), provided the result is a subtype of `bound`.
* (i.e. `inst.widenSingletons <:< bound` succeeds with satisfiable constraint)
* widen (all) the singleton type(s), provided the result is a subtype of `bound`
* (i.e. `inst.widenSingletons <:< bound` succeeds with satisfiable constraint) and
* is not transparent according to `isTransparent`.
* 2a. If `inst` is a union type and `widenUnions` is true, approximate the union type
* from above by an intersection of all common base types, provided the result
* is a subtype of `bound`.
Expand All @@ -647,7 +648,7 @@ trait ConstraintHandling {
def widenOr(tp: Type) =
if widenUnions then
val tpw = tp.widenUnion
if (tpw ne tp) && (tpw <:< bound) then tpw else tp
if (tpw ne tp) && !isTransparent(tpw, traitOnly = false) && (tpw <:< bound) then tpw else tp
else tp.hardenUnions

def widenSingle(tp: Type) =
Expand All @@ -663,11 +664,7 @@ trait ConstraintHandling {
else
val widenedFromSingle = widenSingle(inst)
val widenedFromUnion = widenOr(widenedFromSingle)
val widened =
if (widenedFromUnion ne widenedFromSingle) && isTransparent(widenedFromUnion, traitOnly = false) then
widenedFromSingle
else
dropTransparentTraits(widenedFromUnion, bound)
val widened = dropTransparentTraits(widenedFromUnion, bound)
widenIrreducible(widened)

wideInst match
Expand Down