Mikhail Zarechenskiy
796cdea50e
Consider call `foo(bar())` where bar() returns some type variable `T`;
We had a contract that call `bar` can be completed without completion
of foo (type variables can be inferred from the current context) if `T`
has at least one proper lower constraint (ProperType <: T).
Indeed, new constraints can be added only as upper ones, so there is
no need to grow constraint system.
Unfortunately, we have Exact annotation that is used on return type of
elvis. Now, consider the following situation:
```
fun foo(a: Any) {}
fun bar(e: T): @Exact T
foo(bar("str"))
```
Here, because of Exact annotation, constraint with `Any`-type will be
added as an equal one => our prerequisite that there will be no new
lower constraints is false. `bar("str")` is inferred to Any in OI,
this seems conceptually wrong, but it's another topic of discussion.
In NI we can't just grow constraint system to use outer call because
of another important use-case:
```
fun <T> generic(i: Inv<T>) {}
fun test(a: Inv<*>?, b: Inv<*>) {
generic(a ?: b)
}
```
Common constraint system for these two calls can't be solved
(fundamentally) for this example, only if (a ?: b) and generic(result)
are computed separately.
So, to mitigate initial issue, we'll grow constraint system only if
there is at least one non-proper constraint.
#KT-31969 Fixed
Diagnostic tests format specification
Each diagnostic test consists of a single .kt file containing the code of one or several Kotlin or Java source files. Each diagnostic, be it a warning or an error, is marked in the following way:
<!DIAGNOSTIC_FACTORY_NAME!>element<!>
where DIAGNOSTIC_FACTORY_NAME is the name of the diagnostic which is usually one of the constants in one of Errors* classes.
To test not only the presence of the diagnostic but also the arguments which will be rendered to the user, provide string representations of all of them in the parentheses delimited with ; after the diagnostic name:
return <!TYPE_MISMATCH(String; Nothing)!>"OK"<!>
Note: if you're unsure what text should be added for the parameters, just leave the parentheses empty and the failed test will present the actual values in the assertion message.
Directives
Several directives can be added to the beginning of a test file with the following syntax:
// !DIRECTIVE
1. DIAGNOSTICS
This directive allows to exclude some irrelevant diagnostics (e.g. unused parameter) from a certain test, or to test only a specific set of diagnostics.
The syntax is
'([ + - ! ] DIAGNOSTIC_FACTORY_NAME | ERROR | WARNING | INFO ) +'
where
-
+means 'include'; -
-means 'exclude'; -
!means 'exclude everything but this'.Directives are applied in the order of appearance, i.e.
!FOO +BARmeans include onlyFOOandBAR.
Usage:
// !DIAGNOSTICS: -WARNING +CAST_NEVER_SUCCEEDS
// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE
2. CHECK_TYPE
The directive adds the following declarations to the file:
fun <T> checkSubtype(t: T) = t
class Inv<T>
fun <E> Inv<E>._() {}
infix fun <T> T.checkType(f: Inv<T>.() -> Unit) {}
With that, an exact type of an expression can be checked in the following way:
fun test(expr: A) {
expr checkType { _<A>() }
}
CHECK_TYPE directive also disables UNDERSCORE_USAGE_WITHOUT_BACKTICKS diagnostics output.
Usage:
// !CHECK_TYPE
3. FILE
The directive lets you compose a test consisting of several files in one actual file.
Usage:
// FILE: A.java
/* Java code */
// FILE: B.kt
/* Kotlin code */
4. LANGUAGE
This directive lets you enable or disable certain language features. Language features are named as enum entries of the class LanguageFeature.
Each feature can be enabled with +, disabled with -, or enabled with warning with warn:.
Usage:
// !LANGUAGE: -TopLevelSealedInheritance
// !LANGUAGE: +TypeAliases -LocalDelegatedProperties
// !LANGUAGE: warn:Coroutines
5. API_VERSION
This directive emulates the behavior of the -api-version command line option, disallowing to use declarations annotated with @SinceKotlin(X) where X is greater than the specified API version.
Note that if this directive is present, the NEWER_VERSION_IN_SINCE_KOTLIN diagnostic is automatically disabled, unless the "!DIAGNOSTICS" directive is present.
Usage:
// !API_VERSION: 1.0
6. RENDER_DIAGNOSTICS_MESSAGES
This directive forces Diagnostic printer prints parametrized diagnostics with all parameters.
Usage:
// !RENDER_DIAGNOSTICS_MESSAGES