path: root/doc
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authorMichael Forney <>2017-07-01 14:43:22 -0700
committerOri Bernstein <>2017-07-03 23:27:02 -0700
commit871ef281aaf3c2e8bdff5d92355461bedfa5d933 (patch)
tree76db674822cd67fb1cd1772a8d52f40910735d00 /doc
parentca10a1ec838b7d468a2b43894af659c111a0e9b1 (diff)
Specialize impl declarations on impl type in addition to decl type
This allows multiple specializations of a declarations with a concrete type, which can be selected with the new impl expression if it can't be deduced by its type alone. For example trait hasname @t = Name: byte[:] ;; impl hasname void = Name = "somename" ;; impl hasname bool = Name = "othername" ;; const boolname = impl(Name, void) To do this, pass the param type through to genericname and specializedcl. Since we now need the type parameter to look up trait decls, make sure n->expr.param gets the necessary treatment in typesub, specializenode, pickle, and unpickle. We also need to tag the param types for export.
Diffstat (limited to 'doc')
1 files changed, 3 insertions, 1 deletions
diff --git a/doc/lang.txt b/doc/lang.txt
index 3be5500..d71bb70 100644
--- a/doc/lang.txt
+++ b/doc/lang.txt
@@ -1268,7 +1268,9 @@ TABLE OF CONTENTS:
An impl expression chooses the implementation of the given trait
declaration for the given type. It is useful for refering to trait
- declarations in a generic context.
+ declarations in a generic context. It also allows you to
+ disambiguate a trait declaration whose type does not refer to the
+ trait parameter.
5.2.4. Cast Expressions: