Class used via an implicit conversion to enable two objects to be compared with
===
and !==
with a Boolean
result and an enforced type constraint between
two object types.
Class used via an implicit conversion to enable any two objects to be compared with
===
and !==
with a Boolean
result and no enforced type constraint between
two object types.
Class used via an implicit conversion to enable any two objects to be compared with
===
and !==
with an Option[String]
result and an enforced type constraint between
two object types.
Class used via an implicit conversion to enable any two objects to be compared with
===
and !==
with an Option[String]
result and no enforced type constraint between
two object types.
Returns a TripleEqualsInvocationOnSpread[T]
, given an Spread[T]
, to facilitate
the “<left> should !== (<pivot> +- <tolerance>)
”
syntax of Matchers
.
Returns a TripleEqualsInvocationOnSpread[T]
, given an Spread[T]
, to facilitate
the “<left> should !== (<pivot> +- <tolerance>)
”
syntax of Matchers
.
the Spread[T]
against which to compare the left-hand value
a TripleEqualsInvocationOnSpread
wrapping the passed Spread[T]
value, with
expectingEqual
set to false
.
Returns a TripleEqualsInvocation[Null]
, given a null
reference, to facilitate
the “<left> should !== null
” syntax
of Matchers
.
Returns a TripleEqualsInvocation[Null]
, given a null
reference, to facilitate
the “<left> should !== null
” syntax
of Matchers
.
a null reference
a TripleEqualsInvocation
wrapping the passed null
value, with expectingEqual
set to false
.
Returns a TripleEqualsInvocation[T]
, given an object of type T
, to facilitate
the “<left> should !== <right>
” syntax
of Matchers
.
Returns a TripleEqualsInvocation[T]
, given an object of type T
, to facilitate
the “<left> should !== <right>
” syntax
of Matchers
.
the right-hand side value for an equality assertion
a TripleEqualsInvocation
wrapping the passed right value, with expectingEqual
set to false
.
Returns a TripleEqualsInvocationOnSpread[T]
, given an Spread[T]
, to facilitate
the “<left> should === (<pivot> +- <tolerance>)
”
syntax of Matchers
.
Returns a TripleEqualsInvocationOnSpread[T]
, given an Spread[T]
, to facilitate
the “<left> should === (<pivot> +- <tolerance>)
”
syntax of Matchers
.
the Spread[T]
against which to compare the left-hand value
a TripleEqualsInvocationOnSpread
wrapping the passed Spread[T]
value, with
expectingEqual
set to true
.
Returns a TripleEqualsInvocation[Null]
, given a null
reference, to facilitate
the “<left> should === null
” syntax
of Matchers
.
Returns a TripleEqualsInvocation[Null]
, given a null
reference, to facilitate
the “<left> should === null
” syntax
of Matchers
.
a null reference
a TripleEqualsInvocation
wrapping the passed null
value, with expectingEqual
set to true
.
Returns a TripleEqualsInvocation[T]
, given an object of type T
, to facilitate
the “<left> should === <right>
” syntax
of Matchers
.
Returns a TripleEqualsInvocation[T]
, given an object of type T
, to facilitate
the “<left> should === <right>
” syntax
of Matchers
.
the right-hand side value for an equality assertion
a TripleEqualsInvocation
wrapping the passed right value, with expectingEqual
set to true
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that B
is
implicitly convertible to A
, given an implicit Equivalence[A]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that B
is
implicitly convertible to A
, given an implicit Equivalence[A]
.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[A]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
ConversionCheckedTripleEquals
) and
ConversionCheckedLegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[A]
type class to which the Constraint.areEqual
method will delegate to determine equality.
an implicit conversion from B
to A
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[A]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that A
must be a subtype of B
, given an explicit Equivalence[B]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that A
must be a subtype of B
, given an explicit Equivalence[B]
.
This method is used to enable the Explicitly
DSL for
TypeCheckedTripleEquals
by requiring an explicit Equivalance[B]
, but
taking an implicit function that provides evidence that A
is a subtype of B.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[B]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
LowPriorityTypeCheckedConstraint
(extended by
TypeCheckedTripleEquals
), and
LowPriorityTypeCheckedLegacyConstraint
(extended by
TypeCheckedLegacyTripleEquals
), and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[B]
type class to which the Constraint.areEqual
method
will delegate to determine equality.
evidence that A
is a subype of B
a Constraint[A, B]
whose areEqual
method delegates to the
areEquivalent
method of the passed Equivalence[B]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that A
is
implicitly convertible to B
, given an explicit Equivalence[B]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that A
is
implicitly convertible to B
, given an explicit Equivalence[B]
.
This method is used to enable the Explicitly
DSL for
ConversionCheckedTripleEquals
by requiring an explicit Equivalance[B]
, but
taking an implicit function that converts from A
to B.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[B]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
LowPriorityConversionCheckedConstraint
(extended by
ConversionCheckedTripleEquals
), and
LowPriorityConversionCheckedLegacyConstraint
(extended by
ConversionCheckedLegacyTripleEquals
), and
overriden as non-implicit by the other subtraits in this package.
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[B]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that B
must be a subtype of A
, given an explicit Equivalence[A]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that B
must be a subtype of A
, given an explicit Equivalence[A]
.
This method is used to enable the Explicitly
DSL for
TypeCheckedTripleEquals
by requiring an explicit Equivalance[B]
, but
taking an implicit function that provides evidence that A
is a subtype of B. For example, under TypeCheckedTripleEquals
,
this method (as an implicit method), would be used to compile this statement:
def closeEnoughTo1(num: Double): Boolean = (num === 1.0)(decided by forgivingEquality)
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[A]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
TypeCheckedTripleEquals
) and
TypeCheckedLegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
evidence that B
is a subype of A
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[A]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that B
is
implicitly convertible to A
, given an explicit Equivalence[A]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that B
is
implicitly convertible to A
, given an explicit Equivalence[A]
.
This method is used to enable the Explicitly
DSL for
ConversionCheckedTripleEquals
by requiring an explicit Equivalance[A]
, but
taking an implicit function that converts from B
to A. For example, under ConversionCheckedTripleEquals
,
this method (as an implicit method), would be used to compile this statement:
def closeEnoughTo1(num: Double): Boolean = (num === 1.0)(decided by forgivingEquality)
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[A]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
ConversionCheckedTripleEquals
) and
ConversionCheckedLegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[A]
type class to which the Constraint.areEqual
method will delegate to determine equality.
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[A]
.
Converts to an CheckingEqualizer
that provides ===
and !==
operators
that result in Boolean
and enforce a type constraint.
Converts to an CheckingEqualizer
that provides ===
and !==
operators
that result in Boolean
and enforce a type constraint.
This method is overridden and made implicit by subtraits TypeCheckedTripleEquals
and
ConversionCheckedTripleEquals
, and overriden as
non-implicit by the other subtraits in this package.
the object whose type to convert to CheckingEqualizer
.
if left
is null
.
Converts to an Equalizer
that provides ===
and !==
operators that
result in Boolean
and enforce no type constraint.
Converts to an Equalizer
that provides ===
and !==
operators that
result in Boolean
and enforce no type constraint.
This method is overridden and made implicit by subtrait TripleEquals
and overriden as non-implicit by the other
subtraits in this package.
the object whose type to convert to Equalizer
.
if left
is null
.
Converts to a LegacyCheckingEqualizer
that provides ===
and !==
operators
that result in Option[String]
and enforce a type constraint.
Converts to a LegacyCheckingEqualizer
that provides ===
and !==
operators
that result in Option[String]
and enforce a type constraint.
This method is overridden and made implicit by subtraits TypeCheckedLegacyTripleEquals
and ConversionCheckedLegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
the object whose type to convert to LegacyCheckingEqualizer
.
if left
is null
.
Converts to a LegacyEqualizer
that provides ===
and !==
operators that
result in Option[String]
and enforce no type constraint.
Converts to a LegacyEqualizer
that provides ===
and !==
operators that
result in Option[String]
and enforce no type constraint.
This method is overridden and made implicit by subtrait LegacyTripleEquals
and overriden as non-implicit
by the other subtraits in this package.
the object whose type to convert to LegacyEqualizer
.
if left
is null
.
Returns an Equality[A]
for any type A
that determines equality
by first calling .deep
on any Array
(on either the left or right side),
then comparing the resulting objects with ==
.
Returns an Equality[A]
for any type A
that determines equality
by first calling .deep
on any Array
(on either the left or right side),
then comparing the resulting objects with ==
.
a default Equality
for type A
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that A
is
implicitly convertible to B
, given an implicit Equivalence[B]
.
Provides a Constraint[A, B]
class for any two types A
and B
, enforcing the type constraint that A
is
implicitly convertible to B
, given an implicit Equivalence[B]
.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[B]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
LowPriorityConversionCheckedConstraint
(extended by
ConversionCheckedTripleEquals
), and
LowPriorityConversionCheckedLegacyConstraint
(extended by
ConversionCheckedLegacyTripleEquals
), and
overriden as non-implicit by the other subtraits in this package.
an implicit conversion from A
to B
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[B]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that A
must be a subtype of B
, given an implicit Equivalence[B]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that A
must be a subtype of B
, given an implicit Equivalence[B]
.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[A]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
LowPriorityTypeCheckedConstraint
(extended by
TypeCheckedTripleEquals
), and
LowPriorityTypeCheckedLegacyConstraint
(extended by
TypeCheckedLegacyTripleEquals
), and
overriden as non-implicit by the other subtraits in this package.
an Equivalence[B]
type class to which the Constraint.areEqual
method
will delegate to determine equality.
evidence that A
is a subype of B
a Constraint[A, B]
whose areEqual
method delegates to the
areEquivalent
method of the passed Equivalence[B]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that B
must be a subtype of A
, given an implicit Equivalence[A]
.
Provides a Constraint[A, B]
for any two types A
and B
, enforcing the type constraint
that B
must be a subtype of A
, given an implicit Equivalence[A]
.
The returned Constraint
's areEqual
method uses the implicitly passed Equivalence[A]
's
areEquivalent
method to determine equality.
This method is overridden and made implicit by subtraits
TypeCheckedTripleEquals
) and
TypeCheckedLegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
evidence that B
is a subype of A
a Constraint[A, B]
whose areEqual
method delegates to the areEquivalent
method of
the passed Equivalence[A]
.
Provides a Constraint[A, B]
class for any two types A
and B
, with no type constraint enforced, given an
implicit Equality[A]
.
Provides a Constraint[A, B]
class for any two types A
and B
, with no type constraint enforced, given an
implicit Equality[A]
.
The returned Constraint
's areEqual
method uses the implicitly passed Equality[A]
's
areEqual
method to determine equality.
This method is overridden and made implicit by subtraits TripleEquals
and
LegacyTripleEquals
, and
overriden as non-implicit by the other subtraits in this package.
an Equality[A]
type class to which the Constraint.areEqual
method will delegate to determine equality.
a Constraint[A, B]
whose areEqual
method delegates to the areEqual
method of
the passed Equality[A]
.
Provides
===
and!==
operators that returnBoolean
, delegate the equality determination to anEquality
type class, and require the types of the two values compared to be in a subtype/supertype relationship.TypeCheckedTripleEquals
is useful (in both production and test code) when you need determine equality for a type of object differently than itsequals
method—either you can't change theequals
method, or theequals
method is sensible generally, but you're in a special situation where you need something else—and/or you want to enforce at compile-time that the types of the compared values are in a subtype/supertype relationship.This trait is the strictest of the three triple equals traits, enforcing a stronger constraint than both
TripleEquals
(the most lenient) andConversionCheckedTripleEquals
(the middle ground). IfTripleEquals
is mixed in or imported, the===
can be used with any two types and still compile. IfTypeCheckedTripleEquals
is mixed in or imported, however, only types in a subtype or supertype relationship with each other (including when both types are exactly the same) will compile.ConversionCheckedTripleEquals
is slightly more accomodating, because in addition to compiling any use of===
that will compile underTypeCheckedTripleEquals
, it will also compile type types that would be rejected byTypeCheckedTripleEquals
, so long as an implicit conversion (in either direction) from one type to another is available.For example, under
TypeCheckedTripleEquals
, the following use of===
will not compile, becauseInt
andLong
are not in a subtype/supertype relationship. (I.e.,Int
is not a subtype or supertype ofLong
):Trait
TypeCheckedTripleEquals
rejects typesInt
andLong
because they are not directly related via subtyping. However, an implicit widening conversion fromInt
toLong
does exist (imported implicitly fromscala.Predef
), soConversionCheckedTripleEquals
will allow it:The implicit conversion can go in either direction: from the left type to the right type, or vice versa. In the above expression the implicit conversion goes from left to right (the
Int
on the left to theLong
on the right). It also works the other way:This trait will override or hide implicit methods defined by its sibling traits,
TripleEquals
orConversionCheckedTripleEquals
, and can therefore be used to temporarily turn on or off conversion checking in a limited scope. Here's an example, in whichTypeCheckedTripleEquals
will cause a compiler error:Because
Int
andLong
are not in a subtype/supertype relationship, comparing1
and1L
in the context ofTypeCheckedTripleEquals
will generate a compiler error:You can “relax” the type checking (i.e., by additionally allowing implicitly convertible types) locally by importing the members of
ConversionCheckedTripleEquals
in a limited scope:With the above change, the
Example.scala
file compiles fine. Conversion checking is enabled only inside the firstcmp
method that takes anInt
and aLong
.TypeCheckedTripleEquals
is still enforcing its type constraint, for example, for thes === t
expression in the other overloadedcmp
method that takes strings.Because the methods in
ConversionCheckedTripleEquals
(and its siblings) override all the methods defined in supertypeTripleEqualsSupport
, you can achieve the same kind of nested tuning of equality constraints whether you mix in traits, import from companion objects, or use some combination of both.In short, you should be able to select a primary constraint level via either a mixin or import, then change that in nested scopes however you want, again either through a mixin or import, without getting any implicit conversion ambiguity. The innermost constraint level in scope will always be in force.
An alternative way to solve an unwanted compiler error caused by an over-zealous type constraint is with a widening type ascription. Here are some examples:
Although you could solve the above type error with
ConversionCheckedTripleEquals
, you could also simply widen the type of one side or the other toAny
. BecauseAny
is a supertype of everything, the type constraint will be satisfied:You could alternatively widen a type to a more specific common supertype than
Any
. For example, sinceInt
andLong
are both subtypes ofAnyVal
, you could widen either type toAnyVal
to satisfy the type checker: