Complete better structure to diagnostic messages

5 files changed, 174 insertions, 7 deletions

diff --git a/src/dotty/tools/dotc/reporting/diagnostic/Message.scala b/src/dotty/tools/dotc/reporting/diagnostic/Message.scala
index 90ebf11a2..d7cfa2e2b 100644
--- a/src/dotty/tools/dotc/reporting/diagnostic/Message.scala
+++ b/src/dotty/tools/dotc/reporting/diagnostic/Message.scala
@@ -4,6 +4,7 @@ package reporting
 package diagnostic
 
 import util.SourcePosition
+import core.Contexts.Context
 
 import java.util.Optional
 
@@ -55,9 +56,3 @@ class Message(
   override def toString = s"$getClass at $pos: $message"
   override def getMessage() = message
 }
-
-object NoExplanation {
-  def unapply(m: Message): Option[Message] =
-    if (m.explanation == "") Some(m)
-    else None
-}
diff --git a/src/dotty/tools/dotc/reporting/diagnostic/MessageCreator.scala b/src/dotty/tools/dotc/reporting/diagnostic/MessageCreator.scala
new file mode 100644
index 000000000..d74099f4f
--- /dev/null
+++ b/src/dotty/tools/dotc/reporting/diagnostic/MessageCreator.scala
@@ -0,0 +1,62 @@
+package dotty.tools
+package dotc
+package reporting
+package diagnostic
+
+import util.{SourcePosition, NoSourcePosition}
+import core.Contexts.Context
+
+object MessageCreator {
+  implicit class DiagnosticContext(val c: Context) extends AnyVal {
+    def shouldExplain(msg: MessageCreator): Boolean = {
+      implicit val ctx: Context = c
+      msg match {
+        case NoExplanation(_) => false
+        case _ => ctx.settings.explain.value
+      }
+    }
+  }
+
+  implicit def toNoExplanation(str: String) =
+    new NoExplanation(str)
+}
+
+trait MessageCreator {
+  import messages._
+
+  def msg: String
+  def kind: String
+  def explanation: String
+
+  def error(pos: SourcePosition) =
+    new Error(msg, pos, kind, explanation)
+
+  def warning(pos: SourcePosition) =
+    new Warning(msg, pos, kind, explanation)
+
+  def info(pos: SourcePosition) =
+    new Info(msg, pos, kind, explanation)
+
+  def featureWarnign(pos: SourcePosition) =
+    new FeatureWarning(msg, pos, kind, explanation)
+
+  def uncheckedWarning(pos: SourcePosition) =
+    new UncheckedWarning(msg, pos, kind, explanation)
+
+  def deprecationWarning(pos: SourcePosition) =
+    new DeprecationWarning(msg, pos, kind, explanation)
+
+  def migrationWarning(pos: SourcePosition) =
+    new MigrationWarning(msg, pos, kind, explanation)
+}
+
+class NoExplanation(val msg: String) extends MessageCreator {
+  val explanation = ""
+  val kind = ""
+}
+
+object NoExplanation {
+  def unapply(m: MessageCreator): Option[MessageCreator] =
+    if (m.explanation == "") Some(m)
+    else None
+}
diff --git a/src/dotty/tools/dotc/reporting/diagnostic/basic.scala b/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
index 2da986d89..382e9a295 100644
--- a/src/dotty/tools/dotc/reporting/diagnostic/basic.scala
+++ b/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
@@ -9,7 +9,7 @@ import util.{SourcePosition, NoSourcePosition}
 import config.Settings.Setting
 import interfaces.Diagnostic.{ERROR, WARNING, INFO}
 
-object basic {
+object messages {
 
   class Error(
     msgFn: => String,
diff --git a/src/dotty/tools/dotc/reporting/diagnostic/syntax.scala b/src/dotty/tools/dotc/reporting/diagnostic/syntax.scala
new file mode 100644
index 000000000..675cacbed
--- /dev/null
+++ b/src/dotty/tools/dotc/reporting/diagnostic/syntax.scala
@@ -0,0 +1,63 @@
+package dotty.tools
+package dotc
+package reporting
+package diagnostic
+
+import dotc.core._
+import Contexts.Context, Decorators._, Symbols._
+import dotc.printing.SyntaxHighlighting._
+import util.{SourcePosition, NoSourcePosition}
+
+object syntax {
+  import dotc.ast.Trees._
+  import dotc.ast.untpd
+
+  abstract class EmptyCatchOrFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context) extends MessageCreator {
+    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
+    }
+  }
+
+  class EmptyCatchBlock(tryBody: untpd.Tree)(implicit ctx: Context)
+  extends EmptyCatchOrFinallyBlock(tryBody) {
+    val kind = "Syntax"
+    val msg =
+      hl"""|The ${"catch"} block does not contain a valid expression, try
+           |adding a case like - `${"case e: Exception =>"}` to the block""".stripMargin
+  }
+
+  case class EmptyCatchAndFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context)
+  extends EmptyCatchOrFinallyBlock(tryBody) {
+    val kind = "Syntax"
+    val msg =
+      hl"""|A ${"try"} without ${"catch"} or ${"finally"} is equivalent to putting
+           |its body in a block; no exceptions are handled.""".stripMargin
+  }
+}
diff --git a/src/dotty/tools/dotc/reporting/diagnostic/tpe.scala b/src/dotty/tools/dotc/reporting/diagnostic/tpe.scala
new file mode 100644
index 000000000..4aa24c440
--- /dev/null
+++ b/src/dotty/tools/dotc/reporting/diagnostic/tpe.scala
@@ -0,0 +1,47 @@
+package dotty.tools
+package dotc
+package reporting
+package diagnostic
+
+import dotc.core._
+import Contexts.Context, Decorators._, Symbols._
+import dotc.printing.SyntaxHighlighting._
+import util.{SourcePosition, NoSourcePosition}
+
+object tpe {
+  import dotc.ast.Trees._
+  import dotc.ast.untpd
+
+  class DuplicateBind(
+    bind: untpd.Bind,
+    tree: untpd.CaseDef
+  )(implicit ctx: Context) extends MessageCreator {
+    val kind = "Naming"
+
+    val msg =
+      em"duplicate pattern variable: `${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 bound variables!""".stripMargin
+    }
+  }
+}