Type-annotated inline expression inside implicitNotFound annotation disables it completely

[belamenso]

Compiler version

3.6.2

Minimized code

inline val msg: String = "abc"
trait E[T]
def f(using @annotation.implicitNotFound(msg) e: E[Int]): Unit = ()
@main def hello(): Unit = f

Output

[error] -- [E172] Type Error: Main.scala:5:27 
[error] 5 |@main def hello(): Unit = f
[error]   |                           ^
[error]   |    No given instance of type E[Int] was found for parameter e of method f

Expectation

The error No given instance of type E[Int] was found for parameter e of method f is the default one that was supposed to be customized to abc. The reason this happens is the : String type annotation.

If you just do inline val msg = "abc" then it will work as expected:

[error] -- [E172] Type Error: Main.scala:5:27 
[error] 5 |@main def hello(): Unit = f
[error]   |                           ^
[error]   |                           abc

• inline val msg = "abc" works
• inline val msg = "ab" + "c" works
• inline val msg: String = "abc" does not work (!)
• inline val msg = "cba".reverse does not work

[hamzaremmal]

inline val msg = "cba".reverse does not work

I'm not surprised about this one, and I'm not sure if it should work. If not, it should at least be an error. (It should be it's own issue, can you open it please ?)

inline val msg: String = "abc" does not work (!)

The current code tries to infer the value for it's type. See:

scala3/compiler/src/dotty/tools/dotc/core/Annotations.scala

Line 41 in 5176f9f

for (case ConstantType(c) <- argument(i) map (_.tpe.widenTermRefExpr.normalized)) yield c

So to fix this issue, we should change how values are inlined in this case. Not sure how hard it would be to do.

[belamenso]

Ok, I have changed this one to be about : String, and moved the discussion about more complex things over to #22367 .