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Commit c4c48e3

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Explain no expansion of ContextFunction0 (#23844)
Fixes #21321 Just an edge case. I tried emitting `TypeMismatch` with addenda, but it didn't render, so that was too much hassle just to add a string. This is the existing notice; it doesn't indicate why it doesn't work. ``` 2 |val v1: scala.ContextFunction0[String] = "x" // error | ^^^ | Found: ("x" : String) | Required: () ?=> String ```
2 parents 7762b23 + 3fdc94f commit c4c48e3

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4 files changed

+32
-3
lines changed

4 files changed

+32
-3
lines changed

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

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3751,12 +3751,18 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
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val ifpt = defn.asContextFunctionType(pt)
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val result =
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if ifpt.exists
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&& defn.functionArity(ifpt) > 0 // ContextFunction0 is only used after ElimByName
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&& !ctx.isAfterTyper
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&& {
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// ContextFunction0 is only used after ElimByName
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val arity = defn.functionArity(ifpt)
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if arity == 0 then
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report.error(em"context function types require at least one parameter", xtree.srcPos)
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arity > 0
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}
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&& xtree.isTerm
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&& !untpd.isContextualClosure(xtree)
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&& !ctx.mode.is(Mode.Pattern)
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&& !xtree.isInstanceOf[SplicePattern]
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&& !ctx.isAfterTyper
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&& !ctx.isInlineContext
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then
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makeContextualFunction(xtree, ifpt)

‎tests/neg/context-function-syntax.scala

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ val test =
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(using x: Int) => x // error // error // error
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val f = () ?=> 23 // error
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val g: ContextFunction0[Int] = ??? // ok
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val g: ContextFunction0[Int] = ??? // error at typer for RHS not expanded
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val h: () ?=> Int = ??? // error
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object Example3 extends App {

‎tests/neg/i21321.check

Lines changed: 19 additions & 0 deletions
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@@ -0,0 +1,19 @@
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-- Error: tests/neg/i21321.scala:3:42 ----------------------------------------------------------------------------------
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3 |val v1b: scala.ContextFunction0[String] = () ?=> "x" // error
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| ^^
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| context function literals require at least one formal parameter
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-- Error: tests/neg/i21321.scala:4:8 -----------------------------------------------------------------------------------
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4 |val v2: () ?=> String = "y" // error // error in parser
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| ^^
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| context function types require at least one parameter
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-- Error: tests/neg/i21321.scala:2:41 ----------------------------------------------------------------------------------
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2 |val v1: scala.ContextFunction0[String] = "x" // error
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| ^^^
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| context function types require at least one parameter
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-- [E007] Type Mismatch Error: tests/neg/i21321.scala:4:24 -------------------------------------------------------------
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4 |val v2: () ?=> String = "y" // error // error in parser
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| ^^^
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| Found: ("y" : String)
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| Required: () => String
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|
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| longer explanation available when compiling with `-explain`

‎tests/neg/i21321.scala

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
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val v1: scala.ContextFunction0[String] = "x" // error
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val v1b: scala.ContextFunction0[String] = () ?=> "x" // error
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val v2: () ?=> String = "y" // error // error in parser

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