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Don't emit line number for synthetic unit value (#18717)
Synthetic `()` values are added to blocks without an expression. Don't emit a line number for them. Implemented by checking the `SyntheticUnit` attachment. This seems simpler than trying to control the position assigned to synthetic unit trees, as they are created in many places. Fixes #18320. Forward port of scala/scala#10577
2 parents f62429b + e204e30 commit b71c2d0

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16 files changed

+60
-40
lines changed

16 files changed

+60
-40
lines changed

‎compiler/src/dotty/tools/backend/jvm/BCodeSkelBuilder.scala‎

Lines changed: 22 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -3,26 +3,24 @@ package backend
33
package jvm
44

55
import scala.language.unsafeNulls
6-
76
import scala.annotation.tailrec
8-
9-
import scala.collection.{ mutable, immutable }
10-
7+
import scala.collection.{immutable, mutable}
118
import scala.tools.asm
129
import dotty.tools.dotc.ast.tpd
1310
import dotty.tools.dotc.ast.TreeTypeMap
1411
import dotty.tools.dotc.CompilationUnit
15-
import dotty.tools.dotc.core.Decorators._
16-
import dotty.tools.dotc.core.Flags._
17-
import dotty.tools.dotc.core.StdNames._
18-
import dotty.tools.dotc.core.NameKinds._
12+
import dotty.tools.dotc.ast.Trees.SyntheticUnit
13+
import dotty.tools.dotc.core.Decorators.*
14+
import dotty.tools.dotc.core.Flags.*
15+
import dotty.tools.dotc.core.StdNames.*
16+
import dotty.tools.dotc.core.NameKinds.*
1917
import dotty.tools.dotc.core.Names.TermName
20-
import dotty.tools.dotc.core.Symbols._
21-
import dotty.tools.dotc.core.Types._
22-
import dotty.tools.dotc.core.Contexts._
23-
import dotty.tools.dotc.util.Spans._
18+
import dotty.tools.dotc.core.Symbols.*
19+
import dotty.tools.dotc.core.Types.*
20+
import dotty.tools.dotc.core.Contexts.*
21+
import dotty.tools.dotc.util.Spans.*
2422
import dotty.tools.dotc.report
25-
import dotty.tools.dotc.transform.SymUtils._
23+
import dotty.tools.dotc.transform.SymUtils.*
2624

2725
/*
2826
*
@@ -624,16 +622,17 @@ trait BCodeSkelBuilder extends BCodeHelpers {
624622
case _ => a
625623
}
626624

627-
if (!emitLines || !tree.span.exists) return;
628-
val nr = ctx.source.offsetToLine(tree.span.point) + 1
629-
if (nr != lastEmittedLineNr) {
630-
lastEmittedLineNr = nr
631-
getNonLabelNode(lastInsn) match {
632-
case lnn: asm.tree.LineNumberNode =>
633-
// overwrite previous landmark as no instructions have been emitted for it
634-
lnn.line = nr
635-
case _ =>
636-
mnode.visitLineNumber(nr, currProgramPoint())
625+
if (emitLines && tree.span.exists && !tree.hasAttachment(SyntheticUnit)) {
626+
val nr = ctx.source.offsetToLine(tree.span.point) + 1
627+
if (nr != lastEmittedLineNr) {
628+
lastEmittedLineNr = nr
629+
getNonLabelNode(lastInsn) match {
630+
case lnn: asm.tree.LineNumberNode =>
631+
// overwrite previous landmark as no instructions have been emitted for it
632+
lnn.line = nr
633+
case _ =>
634+
mnode.visitLineNumber(nr, currProgramPoint())
635+
}
637636
}
638637
}
639638
}

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

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1844,7 +1844,7 @@ object desugar {
18441844
case ts: Thicket => ts.trees.tail
18451845
case t => Nil
18461846
} map {
1847-
case Block(Nil, EmptyTree) => Literal(Constant(())) // for s"... ${} ..."
1847+
case Block(Nil, EmptyTree) => unitLiteral // for s"... ${} ..."
18481848
case Block(Nil, expr) => expr // important for interpolated string as patterns, see i1773.scala
18491849
case t => t
18501850
}
@@ -1872,7 +1872,7 @@ object desugar {
18721872
val pats1 = if (tpt.isEmpty) pats else pats map (Typed(_, tpt))
18731873
flatTree(pats1 map (makePatDef(tree, mods, _, rhs)))
18741874
case ext: ExtMethods =>
1875-
Block(List(ext), Literal(Constant(())).withSpan(ext.span))
1875+
Block(List(ext), unitLiteral.withSpan(ext.span))
18761876
case f: FunctionWithMods if f.hasErasedParams => makeFunctionWithValDefs(f, pt)
18771877
}
18781878
desugared.withSpan(tree.span)

‎compiler/src/dotty/tools/dotc/ast/Trees.scala‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -31,6 +31,8 @@ object Trees {
3131

3232
/** Property key for backquoted identifiers and definitions */
3333
val Backquoted: Property.StickyKey[Unit] = Property.StickyKey()
34+
35+
val SyntheticUnit: Property.StickyKey[Unit] = Property.StickyKey()
3436

3537
/** Trees take a parameter indicating what the type of their `tpe` field
3638
* is. Two choices: `Type` or `Untyped`.

‎compiler/src/dotty/tools/dotc/ast/tpd.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -64,7 +64,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
6464
ta.assignType(untpd.Literal(const))
6565

6666
def unitLiteral(using Context): Literal =
67-
Literal(Constant(()))
67+
Literal(Constant(())).withAttachment(SyntheticUnit, ())
6868

6969
def nullLiteral(using Context): Literal =
7070
Literal(Constant(null))

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

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -492,7 +492,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
492492
def InferredTypeTree(tpe: Type)(using Context): TypedSplice =
493493
TypedSplice(new InferredTypeTree().withTypeUnchecked(tpe))
494494

495-
def unitLiteral(implicit src: SourceFile): Literal = Literal(Constant(()))
495+
def unitLiteral(implicit src: SourceFile): Literal = Literal(Constant(())).withAttachment(SyntheticUnit, ())
496496

497497
def ref(tp: NamedType)(using Context): Tree =
498498
TypedSplice(tpd.ref(tp))

‎compiler/src/dotty/tools/dotc/inlines/Inliner.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -793,7 +793,7 @@ class Inliner(val call: tpd.Tree)(using Context):
793793
typed(tree.cond, defn.BooleanType)(using condCtx) match {
794794
case cond1 @ ConstantValue(b: Boolean) =>
795795
val selected0 = if (b) tree.thenp else tree.elsep
796-
val selected = if (selected0.isEmpty) tpd.Literal(Constant(())) else typed(selected0, pt)
796+
val selected = if (selected0.isEmpty) tpd.unitLiteral else typed(selected0, pt)
797797
if (isIdempotentExpr(cond1)) selected
798798
else Block(cond1 :: Nil, selected)
799799
case cond1 =>

‎compiler/src/dotty/tools/dotc/inlines/Inlines.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -408,7 +408,7 @@ object Inlines:
408408
arg match
409409
case ConstantValue(_) | Inlined(_, Nil, Typed(ConstantValue(_), _)) => // ok
410410
case _ => report.error(em"expected a constant value but found: $arg", arg.srcPos)
411-
return Literal(Constant(())).withSpan(call.span)
411+
return unitLiteral.withSpan(call.span)
412412
else if inlinedMethod == defn.Compiletime_codeOf then
413413
return Intrinsics.codeOf(arg, call.srcPos)
414414
case _ =>

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

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -2211,7 +2211,7 @@ object Parsers {
22112211
case _ =>
22122212
}
22132213
patch(source, cond.span.endPos, "}) ()")
2214-
WhileDo(Block(body, cond), Literal(Constant(())))
2214+
WhileDo(Block(body, cond), unitLiteral)
22152215
}
22162216
case TRY =>
22172217
val tryOffset = in.offset
@@ -2241,7 +2241,7 @@ object Parsers {
22412241
in.nextToken();
22422242
val expr = subExpr()
22432243
if expr.span.exists then expr
2244-
else Literal(Constant(())) // finally without an expression
2244+
else unitLiteral // finally without an expression
22452245
}
22462246
else {
22472247
if handler.isEmpty then
@@ -3728,10 +3728,10 @@ object Parsers {
37283728
val stats = selfInvocation() :: (
37293729
if (isStatSep) { in.nextToken(); blockStatSeq() }
37303730
else Nil)
3731-
Block(stats, Literal(Constant(())))
3731+
Block(stats, unitLiteral)
37323732
}
37333733
}
3734-
else Block(selfInvocation() :: Nil, Literal(Constant(())))
3734+
else Block(selfInvocation() :: Nil, unitLiteral)
37353735

37363736
/** SelfInvocation ::= this ArgumentExprs {ArgumentExprs}
37373737
*/

‎compiler/src/dotty/tools/dotc/transform/DropBreaks.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -122,7 +122,7 @@ class DropBreaks extends MiniPhase:
122122
case id: Ident =>
123123
val arg = (args: @unchecked) match
124124
case arg :: Nil => arg
125-
case Nil => Literal(Constant(())).withSpan(tree.span)
125+
case Nil => unitLiteral.withSpan(tree.span)
126126
Some((id.symbol, arg))
127127
case _ => None
128128
case _ => None

‎compiler/src/dotty/tools/dotc/transform/Erasure.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -319,7 +319,7 @@ object Erasure {
319319
cast(tree1, pt)
320320
case _ =>
321321
val cls = pt.classSymbol
322-
if (cls eq defn.UnitClass) constant(tree, Literal(Constant(())))
322+
if (cls eq defn.UnitClass) constant(tree, unitLiteral)
323323
else {
324324
assert(cls ne defn.ArrayClass)
325325
ref(unboxMethod(cls.asClass)).appliedTo(tree)

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