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package dotty.tools
package dotc
package reporting
import dotc.core._
import Contexts.Context, Decorators._, Symbols._
import dotc.printing.SyntaxHighlighting._
import util.{SourcePosition, NoSourcePosition}
object ErrorExplanations {
import dotc.ast.Trees._
import dotc.ast.untpd
implicit def stringToExplanation(s: String) = NoExplanation(s)
implicit class ShouldExplainCtx(val c: Context) extends AnyVal {
def shouldExplain(expl: Explanation): Boolean = {
implicit val ctx = c
expl match {
case _: NoExplanation => false
case expl if ctx.settings.explainerrors.value => true
case _ => false
}
}
}
trait Explanation {
def msg: String
def explanation: String
}
case class NoExplanation(msg: String) extends Explanation {
val explanation = ""
}
abstract class EmptyCatchOrFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context) extends Explanation {
val explanation = {
val tryString = tryBody match {
case Block(Nil, untpd.EmptyTree) => "{}"
case _ => tryBody.show
}
val code1 =
s"""|try $tryString catch {
| case t: Throwable => ???
|}""".stripMargin
val code2 =
s"""|try $tryString finally {
| // perform your cleanup here!
|}""".stripMargin
hl"""|Explanation:
|============
|A ${"try"} expression should be followed by some mechanism to handle any exceptions
|thrown. Typically a ${"catch"} expression follows the ${"try"} and pattern matches
|on any expected exceptions. For example:
|
|$code1
|
|It is also possible to follow a ${"try"} immediately by a ${"finally"} - letting the
|exception propagate - but still allowing for some clean up in ${"finally"}:
|
|$code2
""".stripMargin
}
}
case class EmptyCatchBlock(tryBody: untpd.Tree)(implicit ctx: Context) extends EmptyCatchOrFinallyBlock(tryBody) {
val msg =
hl"""The ${"catch"} block does not contain a valid expression, try adding a case like - `${"case e: Exception =>"}` to the block"""
}
case class EmptyCatchAndFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context) extends EmptyCatchOrFinallyBlock(tryBody) {
val msg =
hl"""A ${"try"} without ${"catch"} or ${"finally"} is equivalent to putting its body in a block; no exceptions are handled."""
}
case class DuplicateBind(bind: untpd.Bind, tree: untpd.CaseDef)(implicit ctx: Context) extends Explanation {
val msg =
em"duplicate pattern variable: `${bind.name}`"
val explanation = {
val pat = tree.pat.show
val guard = tree.guard match {
case untpd.EmptyTree => ""
case guard => s"if ${guard.show}"
}
val body = tree.body match {
case Block(Nil, untpd.EmptyTree) => ""
case body => s" ${body.show}"
}
val caseDef = s"case $pat$guard => $body"
hl"""|Explanation
|===========
|For each ${"case"} bound variable names have to be unique. In:
|
|$caseDef
|
|`${bind.name}` is not unique. Rename one of the binds!""".stripMargin
}
}
}
|
