Fix #4653: check method return type is value type #4844
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|
The following code: trait T {
type S
}
class C {
class D[X](val t: T) {
def bar: t.S = ???
}
val foo: D = new D[Int](???) // error
foo.bar
}gets the following error: -- [E056] Syntax Error: examples/abc.scala:10:11 -------------------------------
10 | val foo: D = new D[Int](???) // error
| ^
| missing type parameter for C.this.D
one error found@Medowhill could you please try if we can produce similar error messages? |
trait T {
type S
}
class C {
class D[X](val t: T) {
def bar: t.S = ???
}
def f(foo: => D) = foo.bar
}It produces the same crash at both master branch and fixed version. It seems handling only method return type is not a complete solution. I'll find a fix works for both value and method. |
| if (tp.isValueType || (tp match { | ||
| case ExprType(tp1) => tp1.isValueType | ||
| case _ => false | ||
| })) tp else ErrorType("A type of a value or a return type of a method should be a value type.")) |
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It's more succinct to write tp.widenExpr.isValueType here. I'm curious which test fails without the widening?
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I'll fix it. Thank you!
When a method has a by-name parameter, typing ValDef of the parameter results ExprType. Therefore, we should allow ExprType, whose result type is ValueType, in addition to ValueType.
| paramFn(typedAheadType(mdef.tpt, tptProto).tpe) | ||
| val tp = typedAheadType(mdef.tpt, tptProto).tpe | ||
| paramFn(if (tp.widenExpr.isValueType) tp | ||
| else ErrorType("A type of a value or a return type of a method should be a value type.")) |
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What about reuse checkSimpleKinded? This way, we don't need to define a new error message and the logic can be reused.
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diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index 8de871adbc3..2933c3dc92a 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -1153,9 +1153,7 @@ class Namer { typer: Typer =>
case _ =>
WildcardType
}
- val tp = typedAheadType(mdef.tpt, tptProto).tpe
- paramFn(if (tp.widenExpr.isValueType) tp
- else ErrorType("A type of a value or a return type of a method should be a value type."))
+ paramFn(checkSimpleKinded(typedAheadType(mdef.tpt, tptProto)).tpe)
}It looks clearer. Thank you!
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