Accept more : at EOLs under -Yindent-colon

Systamtically accept a `:` as COLON when it cannot be confused with a `:` at EOL.

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

@@ -309,6 +309,11 @@ object Parsers {
  offset
  }
 
+ def acceptColon(): Int =
+ val offset = in.offset
+ if in.isColon() then { in.nextToken(); offset }
+ else accept(COLON)
+
  /** semi = nl {nl} | `;'
  * nl = `\n' // where allowed
  */
@@ -861,7 +866,7 @@ object Parsers {
  lookahead.nextToken()
  skipParams()
  skipParams()
- lookahead.token == COLON
+ lookahead.isColon()
 
  def followingIsExtension() =
  val next = in.lookahead.token
@@ -1378,7 +1383,7 @@ object Parsers {
  if isErased then imods = addModifier(imods)
  val paramStart = in.offset
  val ts = funArgType() match {
- case Ident(name) if name != tpnme.WILDCARD && in.token == COLON =>
+ case Ident(name) if name != tpnme.WILDCARD && in.isColon() =>
  isValParamList = true
  funArgTypesRest(
  typedFunParam(paramStart, name.toTermName, imods),
@@ -1467,7 +1472,7 @@ object Parsers {
  /** TypedFunParam ::= id ':' Type */
  def typedFunParam(start: Offset, name: TermName, mods: Modifiers = EmptyModifiers): ValDef =
  atSpan(start) {
- accept(COLON)
+ acceptColon()
  makeParameter(name, typ(), mods)
  }
 
@@ -1761,24 +1766,23 @@ object Parsers {
  else atSpan((t.span union cbs.head.span).start) { ContextBounds(t, cbs) }
  }
 
- def contextBounds(pname: TypeName): List[Tree] = in.token match {
- case COLON =>
+ def contextBounds(pname: TypeName): List[Tree] =
+ if in.isColon() then
  atSpan(in.skipToken()) {
  AppliedTypeTree(toplevelTyp(), Ident(pname))
  } :: contextBounds(pname)
- case VIEWBOUND =>
+ else if in.token == VIEWBOUND then
  report.errorOrMigrationWarning(
  "view bounds `<%' are no longer supported, use a context bound `:' instead",
  in.sourcePos())
  atSpan(in.skipToken()) {
  Function(Ident(pname) :: Nil, toplevelTyp())
  } :: contextBounds(pname)
- case _ =>
+ else
  Nil
- }
 
  def typedOpt(): Tree =
- if (in.token == COLON) { in.nextToken(); toplevelTyp() }
+ if in.isColon() then { in.nextToken(); toplevelTyp() }
  else TypeTree().withSpan(Span(in.lastOffset))
 
  def typeDependingOn(location: Location): Tree =
@@ -2195,6 +2199,7 @@ object Parsers {
  * | SimpleExpr `.` MatchClause
  * | SimpleExpr (TypeArgs | NamedTypeArgs)
  * | SimpleExpr1 ArgumentExprs
+ * | SimpleExpr1 `:` nl ArgumentExprs
  * Quoted ::= ‘'’ ‘{’ Block ‘}’
  * | ‘'’ ‘[’ Type ‘]’
  */
@@ -2342,10 +2347,9 @@ object Parsers {
  lookahead.nextToken()
  if (lookahead.token == RPAREN)
  !fn.isInstanceOf[Trees.Apply[?]] // allow one () as annotation argument
- else if (lookahead.token == IDENTIFIER) {
+ else if lookahead.token == IDENTIFIER then
  lookahead.nextToken()
- lookahead.token != COLON
- }
+ !lookahead.isColon()
  else in.canStartExprTokens.contains(lookahead.token)
  }
  }
@@ -2762,7 +2766,7 @@ object Parsers {
  if allowed.contains(in.token)
  || in.isSoftModifier
  && localModifierTokens.subsetOf(allowed) // soft modifiers are admissible everywhere local modifiers are
- && in.lookahead.token != COLON
+ && !in.lookahead.isColon()
  then
  val isAccessMod = accessModifierTokens contains in.token
  val mods1 = addModifier(mods)
@@ -2931,7 +2935,7 @@ object Parsers {
  }
  atSpan(start, nameStart) {
  val name = ident()
- accept(COLON)
+ acceptColon()
  if (in.token == ARROW && ofClass && !mods.is(Local))
  syntaxError(VarValParametersMayNotBeCallByName(name, mods.is(Mutable)))
  val tpt = paramType()
@@ -2969,7 +2973,7 @@ object Parsers {
  val isParams =
  !impliedMods.is(Given)
  || startParamTokens.contains(in.token)
- || isIdent && (in.name == nme.inline || in.lookahead.token == COLON)
+ || isIdent && (in.name == nme.inline || in.lookahead.isColon())
  if isParams then commaSeparated(() => param())
  else contextTypes(ofClass, nparams)
  checkVarArgsRules(clause)
@@ -3191,13 +3195,7 @@ object Parsers {
  case _ =>
  first :: Nil
  }
- def emptyType = TypeTree().withSpan(Span(in.lastOffset))
- val tpt =
- if (in.token == COLON) {
- in.nextToken()
- toplevelTyp()
- }
- else emptyType
+ val tpt = typedOpt()
  val rhs =
  if tpt.isEmpty || in.token == EQUALS then
  accept(EQUALS)
@@ -3276,15 +3274,7 @@ object Parsers {
  var name = ident.name.asTermName
  val tparams = typeParamClauseOpt(ParamOwner.Def)
  val vparamss = paramClauses(numLeadParams = numLeadParams)
- var tpt = fromWithinReturnType {
- if in.token == COLONEOL then in.token = COLON
- // a hack to allow
- //
- // def f():
- // T
- //
- typedOpt()
- }
+ var tpt = fromWithinReturnType { typedOpt() }
  if (migrateTo3) newLineOptWhenFollowedBy(LBRACE)
  val rhs =
  if in.token == EQUALS then
@@ -3528,7 +3518,7 @@ object Parsers {
  else Nil
  newLinesOpt()
  val noParams = tparams.isEmpty && vparamss.isEmpty
- if !(name.isEmpty && noParams) then accept(COLON)
+ if !(name.isEmpty && noParams) then acceptColon()
  val parents =
  if isSimpleLiteral then rejectWildcardType(annotType()) :: Nil
  else constrApp() :: withConstrApps()
@@ -3570,7 +3560,7 @@ object Parsers {
  isUsingClause(extParams)
  do ()
  leadParamss ++= paramClauses(givenOnly = true, numLeadParams = nparams)
- if in.token == COLON then
+ if in.isColon() then
  syntaxError("no `:` expected here")
  in.nextToken()
  val methods =

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

@@ -76,6 +76,14 @@ object Scanners {
  def isNestedStart = token == LBRACE || token == INDENT
  def isNestedEnd = token == RBRACE || token == OUTDENT
 
+ /** Is token a COLON, after having converted COLONEOL to COLON?
+ * The conversion means that indentation is not significant after `:`
+ * anymore. So, warning: this is a side-effecting operation.
+ */
+ def isColon() =
+ if token == COLONEOL then token = COLON
+ token == COLON
+
  /** Is current token first one after a newline? */
  def isAfterLineEnd: Boolean = lineOffset >= 0