Change layout of ErrorMessages

Author: felixmulder

src/dotty/tools/dotc/parsing/JavaParsers.scala

@@ -29,6 +29,7 @@ import scala.reflect.internal.util.Collections._
 object JavaParsers {
 
   import ast.untpd._
+  import reporting.ErrorMessages.Syntax._
 
   class JavaParser(source: SourceFile)(implicit ctx: Context) extends ParserCommon(source) {
 

src/dotty/tools/dotc/parsing/MarkupParsers.scala

@@ -32,6 +32,7 @@ import Utility._
 object MarkupParsers {
 
   import ast.untpd._
+  import reporting.ErrorMessages.Syntax._
 
   case object MissingEndTagControl extends ControlThrowable {
     override def getMessage = "start tag was here: "

src/dotty/tools/dotc/parsing/Parsers.scala

@@ -17,7 +17,7 @@ import ast.Trees._
 import Decorators._
 import StdNames._
 import util.Positions._
-import reporting.ErrorExplanations._
+import reporting.ErrorMessages._
 import Constants._
 import ScriptParsers._
 import scala.annotation.{tailrec, switch}
@@ -28,6 +28,7 @@ import Scanners.Comment
 object Parsers {
 
   import ast.untpd._
+  import reporting.ErrorMessages.Syntax._
 
   case class OpInfo(operand: Tree, operator: Name, offset: Offset)
 
@@ -87,7 +88,7 @@ object Parsers {
     /** Issue an error at given offset if beyond last error offset
       *  and update lastErrorOffset.
       */
-    def syntaxError(expl: Explanation, offset: Int = in.offset): Unit =
+    def syntaxError(expl: ErrorMessage, offset: Int = in.offset): Unit =
       if (offset > lastErrorOffset) {
         syntaxError(expl, Position(offset))
         lastErrorOffset = in.offset
@@ -96,7 +97,7 @@ object Parsers {
     /** Unconditionally issue an error at given position, without
       *  updating lastErrorOffset.
       */
-    def syntaxError(expl: Explanation, pos: Position): Unit =
+    def syntaxError(expl: ErrorMessage, pos: Position): Unit =
       ctx.explainError(expl, source atPos pos)
 
   }
@@ -203,7 +204,7 @@ object Parsers {
       }
     }
 
-    def warning(msg: Explanation, offset: Int = in.offset) =
+    def warning(msg: ErrorMessage, offset: Int = in.offset) =
       ctx.explainWarning(msg, source atPos Position(offset))
 
     def deprecationWarning(msg: String, offset: Int = in.offset) =

src/dotty/tools/dotc/reporting/ErrorMessages.scala

@@ -0,0 +1,117 @@
+package dotty.tools
+package dotc
+package reporting
+
+import dotc.core._
+import Contexts.Context, Decorators._, Symbols._
+import dotc.printing.SyntaxHighlighting._
+import util.{SourcePosition, NoSourcePosition}
+
+object ErrorMessages {
+  import dotc.ast.Trees._
+  import dotc.ast.untpd
+
+  implicit class ShouldExplainCtx(val c: Context) extends AnyVal {
+    def shouldExplain(expl: ErrorMessage): Boolean = {
+      implicit val ctx = c
+      expl match {
+        case _: NoExplanation => false
+        case expl if ctx.settings.explainerrors.value => true
+        case _ => false
+      }
+    }
+  }
+
+  trait ErrorMessage {
+    def kind: String
+    def msg: String
+    def explanation: String
+  }
+
+  case class NoExplanation(msg: String)(implicit val kind: String) extends ErrorMessage {
+    val explanation = ""
+  }
+
+  object Syntax {
+    implicit val kind: String = "Syntax"
+    implicit def stringToErrorMessage(s: String): ErrorMessage = NoExplanation(s)
+
+    abstract class EmptyCatchOrFinallyBlock(tryBody: untpd.Tree)(implicit ctx: Context, val kind: String) extends ErrorMessage {
+      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, override val kind: String)
+    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, override val kind: String)
+    extends EmptyCatchOrFinallyBlock(tryBody) {
+      val msg =
+        hl"""A ${"try"} without ${"catch"} or ${"finally"} is equivalent to putting its body in a block; no exceptions are handled."""
+    }
+  }
+
+  object Type {
+    implicit val kind: String = "Type"
+    implicit def stringToErrorMessage(s: String): ErrorMessage = NoExplanation(s)
+
+    case class DuplicateBind(bind: untpd.Bind, tree: untpd.CaseDef)(implicit ctx: Context, val kind: String) extends ErrorMessage {
+      val msg =
+        em"duplicate pattern variable: `${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
+      }
+    }
+  }
+}

src/dotty/tools/dotc/reporting/Examples.scala

@@ -13,7 +13,7 @@ import java.lang.System.currentTimeMillis
 import core.Mode
 import interfaces.Diagnostic.{ERROR, WARNING, INFO}
 import dotty.tools.dotc.core.Symbols.Symbol
-import ErrorExplanations._
+import ErrorMessages._
 
 object Reporter {
   class Error(msgFn: => String, pos: SourcePosition) extends Diagnostic(msgFn, pos, ERROR)
@@ -96,10 +96,10 @@ trait Reporting { this: Context =>
   def warning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new Warning(msg, pos))
 
-  def explainWarning(expl: => Explanation, pos: SourcePosition = NoSourcePosition): Unit = {
-    warning(expl.msg, pos)
-    if (this.shouldExplain(expl))
-      reporter.report(new Info(expl.explanation, NoSourcePosition))
+  def explainWarning(err: => ErrorMessage, pos: SourcePosition = NoSourcePosition): Unit = {
+    warning(err.msg, pos)
+    if (this.shouldExplain(err))
+      reporter.report(new Info(err.explanation, NoSourcePosition))
   }
 
   def strictWarning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
@@ -111,10 +111,10 @@ trait Reporting { this: Context =>
     reporter.report(new Error(msg, pos))
   }
 
-  def explainError(expl: => Explanation, pos: SourcePosition = NoSourcePosition): Unit = {
-    error(expl.msg, pos)
-    if (this.shouldExplain(expl))
-      reporter.report(new Info(expl.explanation, NoSourcePosition))
+  def explainError(err: => ErrorMessage, pos: SourcePosition = NoSourcePosition): Unit = {
+    error(err.msg, pos)
+    if (this.shouldExplain(err))
+      reporter.report(new Info(err.explanation, NoSourcePosition))
   }
 
   def errorOrMigrationWarning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =

src/dotty/tools/dotc/reporting/Reporter.scala

@@ -37,7 +37,7 @@ import NavigateAST._
 import transform.SymUtils._
 import language.implicitConversions
 import printing.SyntaxHighlighting._
-import reporting.ErrorExplanations._
+import reporting.ErrorMessages._
 
 object Typer {
 
@@ -65,6 +65,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
   import tpd.{cpy => _, _}
   import untpd.cpy
   import Dynamic.isDynamicMethod
+  import reporting.ErrorMessages.Type._
 
   /** A temporary data item valid for a single typed ident:
    *  The set of all root import symbols that have been