Indentation warning is a syntax warning

Author: som-snytt

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

@@ -712,9 +712,7 @@ object Parsers {
           if in.isNewLine && !(nextIndentWidth < startIndentWidth) then
             warning(
               if startIndentWidth <= nextIndentWidth then
-                em"""Line is indented too far to the right, or a `{` is missing before:
-                  |
-                  |${t.tryToShow}"""
+                IndentationWarning(missing = LBRACE, before = t.tryToShow)
               else
                 in.spaceTabMismatchMsg(startIndentWidth, nextIndentWidth),
               in.next.offset
@@ -729,7 +727,7 @@ object Parsers {
       if in.isNewLine then
         val nextIndentWidth = in.indentWidth(in.next.offset)
         if in.currentRegion.indentWidth < nextIndentWidth && in.currentRegion.closedBy == OUTDENT then
-          warning(em"Line is indented too far to the right, or a `{` or `:` is missing", in.next.offset)
+          warning(IndentationWarning(missing = Seq(LBRACE, COLONop)*), in.next.offset)
 
 /* -------- REWRITES ----------------------------------------------------------- */
 

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -20,7 +20,7 @@ import config.Feature
 import config.Feature.{migrateTo3, sourceVersion}
 import config.SourceVersion.{`3.0`, `3.0-migration`}
 import config.MigrationVersion
-import reporting.{NoProfile, Profile, Message}
+import reporting.*
 
 import java.util.Objects
 import dotty.tools.dotc.reporting.Message.rewriteNotice
@@ -652,7 +652,7 @@ object Scanners {
                   if r.enclosing.isClosedByUndentAt(nextWidth) then
                     insert(OUTDENT, offset)
                 else if r.isInstanceOf[InBraces] && !closingRegionTokens.contains(token) then
-                  report.warning("Line is indented too far to the left, or a `}` is missing", sourcePos())
+                  report.warning(IndentationWarning(isLeft = true, missing = RBRACE), sourcePos())
         else if lastWidth < nextWidth
              || lastWidth == nextWidth && (lastToken == MATCH || lastToken == CATCH) && token == CASE then
           if canStartIndentTokens.contains(lastToken) then

compiler/src/dotty/tools/dotc/reporting/ErrorMessageID.scala

@@ -237,6 +237,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case RecurseWithDefaultID // errorNumber: 221
   case EncodedPackageNameID // errorNumber: 222
   case AmbiguousTemplateNameID // errorNumber: 223
+  case IndentationWarningID // errorNumber: 224
 
   def errorNumber = ordinal - 1
 

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -9,7 +9,7 @@ import Denotations.SingleDenotation
 import SymDenotations.SymDenotation
 import NameKinds.{WildcardParamName, ContextFunctionParamName}
 import parsing.Scanners.Token
-import parsing.Tokens
+import parsing.Tokens, Tokens.showToken
 import printing.Highlighting.*
 import printing.Formatting
 import ErrorMessageID.*
@@ -1232,12 +1232,12 @@ extends ReferenceMsg(ForwardReferenceExtendsOverDefinitionID) {
 class ExpectedTokenButFound(expected: Token, found: Token, prefix: String = "", suffix: String = "")(using Context)
 extends SyntaxMsg(ExpectedTokenButFoundID) {
 
-  private def foundText = Tokens.showToken(found)
+  private def foundText = showToken(found)
 
   def msg(using Context) =
     val expectedText =
       if (Tokens.isIdentifier(expected)) "an identifier"
-      else Tokens.showToken(expected)
+      else showToken(expected)
     i"""$prefix$expectedText expected, but $foundText found$suffix"""
 
   def explain(using Context) =
@@ -1928,7 +1928,7 @@ class ExtendFinalClass(clazz:Symbol, finalClazz: Symbol)(using Context)
 
 class ExpectedTypeBoundOrEquals(found: Token)(using Context)
   extends SyntaxMsg(ExpectedTypeBoundOrEqualsID) {
-  def msg(using Context) = i"${hl("=")}, ${hl(">:")}, or ${hl("<:")} expected, but ${Tokens.showToken(found)} found"
+  def msg(using Context) = i"${hl("=")}, ${hl(">:")}, or ${hl("<:")} expected, but ${showToken(found)} found"
 
   def explain(using Context) =
     i"""Type parameters and abstract types may be constrained by a type bound.
@@ -3745,3 +3745,14 @@ class AmbiguousTemplateName(tree: NamedDefTree[?])(using Context) extends Syntax
   override protected def msg(using Context) = i"name `${tree.name}` should be enclosed in backticks"
   override protected def explain(using Context): String =
     "Names with trailing operator characters may fuse with a subsequent colon if not set off by backquotes or spaces."
+
+class IndentationWarning(isLeft: Boolean = false, before: String = "", missing: Token*)(using Context)
+extends SyntaxMsg(IndentationWarningID):
+  override protected def msg(using Context) =
+    s"Line is indented too far to the ${if isLeft then "left" else "right"}, or a ${
+      missing.map(showToken).mkString(" or ")
+    } is missing${
+      if !before.isEmpty then i" before:\n\n$before" else ""
+    }"
+  override protected def explain(using Context): String =
+    "Indentation that does not reflect syntactic nesting may be due to a typo such as missing punctuation."

tests/warn/i16072.check

@@ -1,7 +1,9 @@
--- Warning: tests/warn/i16072.scala:4:2 --------------------------------------------------------------------------------
+-- [E223] Syntax Warning: tests/warn/i16072.scala:4:2 ------------------------------------------------------------------
 4 |  def x = 1 // warn too far right
   |  ^
-  |  Line is indented too far to the right, or a `{` or `:` is missing
+  |  Line is indented too far to the right, or a '{' or ':' is missing
+  |
+  | longer explanation available when compiling with `-explain`
 -- [E222] Syntax Warning: tests/warn/i16072.scala:3:7 ------------------------------------------------------------------
 3 |object Hello_: // warn colon in name without backticks because the body is empty
   |       ^^^^^^^
@@ -12,10 +14,12 @@
 12 |object :: : // warn deprecated colon without backticks for operator name
    |          ^
    |          `:` after symbolic operator is deprecated; use backticks around operator instead
--- Warning: tests/warn/i16072.scala:21:2 -------------------------------------------------------------------------------
+-- [E223] Syntax Warning: tests/warn/i16072.scala:21:2 -----------------------------------------------------------------
 21 |  def y = 1 // warn
    |  ^
-   |  Line is indented too far to the right, or a `{` or `:` is missing
+   |  Line is indented too far to the right, or a '{' or ':' is missing
+   |
+   | longer explanation available when compiling with `-explain`
 -- [E222] Syntax Warning: tests/warn/i16072.scala:20:6 -----------------------------------------------------------------
 20 |class Uhoh_: // warn
    |      ^^^^^^