Improve description of given instances in error messages

Fixes #11066

Author: odersky

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -426,6 +426,8 @@ class PlainPrinter(_ctx: Context) extends Printer {
     else if (sym.isType) "type"
     else if (sym.isGetter) "getter"
     else if (sym.isSetter) "setter"
+    else if sym.is(Param) then "parameter"
+    else if sym.is(Given) then "given instance"
     else if (flags.is(Lazy)) "lazy value"
     else if (flags.is(Mutable)) "variable"
     else if (sym.isClassConstructor && sym.isPrimaryConstructor) "primary constructor"

tests/neg-macros/i9014.check

@@ -7,4 +7,4 @@
   |
   |                         given_Bar
   |
-  |                     But method given_Bar does not match type Bar.
+  |                     But given instance given_Bar does not match type Bar.

tests/neg/abstract-givens.check

@@ -5,10 +5,10 @@
 -- Error: tests/neg/abstract-givens.scala:8:8 --------------------------------------------------------------------------
 8 |  given y(using Int): String = summon[Int].toString * 22 // error
   |        ^
-  |        error overriding method y in trait T of type (using x$1: Int): String;
-  |          method y of type (using x$1: Int): String cannot override final member method y in trait T
+  |      error overriding given instance y in trait T of type (using x$1: Int): String;
+  |        given instance y of type (using x$1: Int): String cannot override final member given instance y in trait T
 -- Error: tests/neg/abstract-givens.scala:9:8 --------------------------------------------------------------------------
 9 |  given z[T](using T): Seq[T] = List(summon[T]) // error
   |        ^
-  |        error overriding method z in trait T of type [T](using x$1: T): List[T];
-  |          method z of type [T](using x$1: T): Seq[T] has incompatible type
+  |        error overriding given instance z in trait T of type [T](using x$1: T): List[T];
+  |          given instance z of type [T](using x$1: T): Seq[T] has incompatible type

tests/neg/exports.check

@@ -10,7 +10,7 @@
 -- Error: tests/neg/exports.scala:25:21 --------------------------------------------------------------------------------
 25 |    export printUnit.bitmap         // error: no eligible member
    |                     ^
-   |                     non-private method bitmap in class Copier refers to private value printUnit
+   |                     non-private given instance bitmap in class Copier refers to private value printUnit
    |                     in its type signature => Copier.this.printUnit.bitmap$
 -- [E120] Naming Error: tests/neg/exports.scala:23:33 ------------------------------------------------------------------
 23 |    export printUnit.{stat => _, _} // error: double definition

tests/neg/i11066.check

@@ -0,0 +1,4 @@
+-- Error: tests/neg/i11066.scala:15:37 ---------------------------------------------------------------------------------
+15 |val x = Greeter.greet("Who's there?") // error
+   |                                     ^
+   |ambiguous implicit arguments: both given instance joesPrompt in object JoesPrefs and given instance jillsPrompt in object JillsPrefs match type PreferredPrompt of parameter prompt of method greet in object Greeter

tests/neg/i11066.scala

@@ -0,0 +1,15 @@
+class PreferredPrompt(val preference: String)
+object Greeter:
+  def greet(name: String)(using prompt: PreferredPrompt) =
+    println(s"Welcome, $name. The system is ready.")
+    println(prompt.preference)
+object JillsPrefs:
+  given jillsPrompt: PreferredPrompt =
+    PreferredPrompt("Your wish> ")
+object JoesPrefs:
+  given joesPrompt: PreferredPrompt =
+    PreferredPrompt("relax> ")
+
+import JillsPrefs.jillsPrompt
+import JoesPrefs.joesPrompt
+val x = Greeter.greet("Who's there?") // error

tests/neg/i9014.check

@@ -6,4 +6,4 @@
   |
   |                         Bar.given_Bar
   |
-  |                     But method given_Bar in object Bar does not match type Bar.
+  |                     But given instance given_Bar in object Bar does not match type Bar.

tests/neg/missing-implicit2.check

@@ -1,7 +1,7 @@
 -- Error: tests/neg/missing-implicit2.scala:10:18 ----------------------------------------------------------------------
 10 |    f(using xFromY) // error
    |                  ^
-   |                  no implicit argument of type Y was found for parameter y of method xFromY
+   |                  no implicit argument of type Y was found for parameter y of given instance xFromY
    |
    |                  The following import might fix the problem:
    |