Fix #1503: be more careful where to insert apply

src/dotty/tools/dotc/ast/Desugar.scala

@@ -699,7 +699,7 @@ object desugar {
         Apply(Select(left, op), args)
       } else {
         val x = ctx.freshName().toTermName
-        Block(
+        new InfixOpBlock(
           ValDef(x, TypeTree(), left).withMods(synthetic),
           Apply(Select(right, op), Ident(x)))
       }

src/dotty/tools/dotc/ast/untpd.scala

@@ -63,6 +63,16 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   class PolyTypeDef(name: TypeName, override val tparams: List[TypeDef], rhs: Tree)
     extends TypeDef(name, rhs)
 
+  /** A block arising from a right-associative infix operation, where, e.g.
+   *
+   *     a +: b
+   *
+   *  is expanded to
+   *
+   *     { val x = a; b.+:(x) }
+   */
+  class InfixOpBlock(leftOperand: Tree, rightOp: Tree) extends Block(leftOperand :: Nil, rightOp)
+
   // ----- TypeTrees that refer to other tree's symbols -------------------
 
   /** A type tree that gets its type from some other tree's symbol. Enters the

src/dotty/tools/dotc/core/Types.scala

@@ -927,14 +927,17 @@ object Types {
     def narrow(implicit ctx: Context): TermRef =
       TermRef(NoPrefix, ctx.newSkolem(this))
 
-    /** Useful for diagnsotics: The underlying type if this type is a type proxy,
+    /** Useful for diagnostics: The underlying type if this type is a type proxy,
      *  otherwise NoType
      */
     def underlyingIfProxy(implicit ctx: Context) = this match {
       case this1: TypeProxy => this1.underlying
       case _ => NoType
     }
 
+  	/** If this is a FunProto or PolyProto, WildcardType, otherwise this. */
+    def notApplied: Type = this
+
     // ----- Normalizing typerefs over refined types ----------------------------
 
     /** If this normalizes* to a refinement type that has a refinement for `name` (which might be followed

src/dotty/tools/dotc/typer/Applications.scala

@@ -652,7 +652,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
 
   /** Overridden in ReTyper to handle primitive operations that can be generated after erasure */
   protected def handleUnexpectedFunType(tree: untpd.Apply, fun: Tree)(implicit ctx: Context): Tree =
-    throw new Error(s"unexpected type.\n fun = $fun,\n methPart(fun) = ${methPart(fun)},\n methPart(fun).tpe = ${methPart(fun).tpe},\n tpe = ${fun.tpe}")
+    throw new Error(i"unexpected type.\n fun = $fun,\n methPart(fun) = ${methPart(fun)},\n methPart(fun).tpe = ${methPart(fun).tpe},\n tpe = ${fun.tpe}")
 
   def typedNamedArgs(args: List[untpd.Tree])(implicit ctx: Context) =
     for (arg @ NamedArg(id, argtpt) <- args) yield {

src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -182,6 +182,8 @@ object ProtoTypes {
       if ((args eq this.args) && (resultType eq this.resultType) && (typer eq this.typer)) this
       else new FunProto(args, resultType, typer)
 
+    override def notApplied = WildcardType
+
     /** Forget the types of any arguments that have been typed producing a constraint in a
      *  typer state that is not yet committed into the one of the current context `ctx`.
      *  This is necessary to avoid "orphan" PolyParams that are referred to from
@@ -319,6 +321,8 @@ object ProtoTypes {
       if ((targs eq this.targs) && (resType eq this.resType)) this
       else PolyProto(targs, resType)
 
+    override def notApplied = WildcardType
+
     def map(tm: TypeMap)(implicit ctx: Context): PolyProto =
       derivedPolyProto(targs mapConserve tm, tm(resultType))
 

src/dotty/tools/dotc/typer/Typer.scala

@@ -572,7 +572,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
   def typedBlock(tree: untpd.Block, pt: Type)(implicit ctx: Context) = track("typedBlock") {
     val exprCtx = index(tree.stats)
     val stats1 = typedStats(tree.stats, ctx.owner)
-    val expr1 = typedExpr(tree.expr, pt)(exprCtx)
+    val ept =
+      if (tree.isInstanceOf[untpd.InfixOpBlock])
+        // Right-binding infix operations are expanded to InfixBlocks, which may be followed by arguments.
+        // Example: `(a /: bs)(op)` expands to `{ val x = a; bs./:(x) } (op)` where `{...}` is an InfixBlock.
+        pt
+      else pt.notApplied
+    val expr1 = typedExpr(tree.expr, ept)(exprCtx)
     ensureNoLocalRefs(
         assignType(cpy.Block(tree)(stats1, expr1), stats1, expr1), pt, localSyms(stats1))
   }
@@ -619,8 +625,8 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
 
   def typedIf(tree: untpd.If, pt: Type)(implicit ctx: Context) = track("typedIf") {
     val cond1 = typed(tree.cond, defn.BooleanType)
-    val thenp1 = typed(tree.thenp, pt)
-    val elsep1 = typed(tree.elsep orElse (untpd.unitLiteral withPos tree.pos), pt)
+    val thenp1 = typed(tree.thenp, pt.notApplied)
+    val elsep1 = typed(tree.elsep orElse (untpd.unitLiteral withPos tree.pos), pt.notApplied)
     val thenp2 :: elsep2 :: Nil = harmonize(thenp1 :: elsep1 :: Nil)
     assignType(cpy.If(tree)(cond1, thenp2, elsep2), thenp2, elsep2)
   }
@@ -793,7 +799,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
         val selType = widenForMatchSelector(
             fullyDefinedType(sel1.tpe, "pattern selector", tree.pos))
 
-        val cases1 = typedCases(tree.cases, selType, pt)
+        val cases1 = typedCases(tree.cases, selType, pt.notApplied)
         val cases2 = harmonize(cases1).asInstanceOf[List[CaseDef]]
         assignType(cpy.Match(tree)(sel1, cases2), cases2)
     }
@@ -920,8 +926,8 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
   }
 
   def typedTry(tree: untpd.Try, pt: Type)(implicit ctx: Context): Try = track("typedTry") {
-    val expr1 = typed(tree.expr, pt)
-    val cases1 = typedCases(tree.cases, defn.ThrowableType, pt)
+    val expr1 = typed(tree.expr, pt.notApplied)
+    val cases1 = typedCases(tree.cases, defn.ThrowableType, pt.notApplied)
     val finalizer1 = typed(tree.finalizer, defn.UnitType)
     val expr2 :: cases2x = harmonize(expr1 :: cases1)
     val cases2 = cases2x.asInstanceOf[List[CaseDef]]
@@ -1535,8 +1541,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     }
 
   /** If this tree is a select node `qual.name`, try to insert an implicit conversion
-   *  `c` around `qual` so that `c(qual).name` conforms to `pt`. If that fails
-   *  return `tree` itself.
+   *  `c` around `qual` so that `c(qual).name` conforms to `pt`.
    */
   def tryInsertImplicitOnQualifier(tree: Tree, pt: Type)(implicit ctx: Context): Option[Tree] = ctx.traceIndented(i"try insert impl on qualifier $tree $pt") {
     tree match {

tests/neg/i1503.scala

@@ -0,0 +1,14 @@
+object Test {
+
+  val cond = true
+  def foo1() = println("hi")
+  def bar1() = println("there")
+
+  def foo2(x: Int) = println("hi")
+  def bar2(x: Int) = println("there")
+
+  def main(args: Array[String]) = {
+    (if (cond) foo1 else bar1)() // error: Unit does not take parameters
+    (if (cond) foo2 else bar2)(22) // error: missing arguments // error: missing arguments
+  }
+}

tests/run/i1503.check

@@ -0,0 +1,5 @@
+hello
+hi
+33
+hi
+hi

tests/run/i1503.scala

@@ -0,0 +1,38 @@
+object Test {
+
+  def test1() =
+    (new Function0[Unit] {
+      def apply() = println("hello")
+    })()
+
+  val cond = true
+  val foo = () => println("hi")
+  val bar = () => println("there")
+
+  val baz = (x: Int) => println(x)
+
+  def test2() =
+    (if (cond) foo else bar)()
+
+  def test2a() =
+    (if (cond) baz else baz)(33)
+
+  def test3() =
+    (try foo
+     catch { case ex: Exception => bar }
+     finally ())()
+
+  def test4() =
+    (cond match {
+      case true => foo
+      case false => bar
+    })()
+
+  def main(args: Array[String]) = {
+    test1()
+    test2()
+    test2a()
+    test3()
+    test4()
+  }
+}