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Performance optimization: only compute stack traces when needed #16616

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Merged
merged 2 commits into from
Jan 6, 2023
Merged

Performance optimization: only compute stack traces when needed #16616

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108a3c6
TypeError: only compute the stack trace when needed
smarter Jan 4, 2023
49947f9
SuspendException: Do not compute the stack trace since we never use it
smarter Jan 4, 2023
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3 changes: 2 additions & 1 deletion compiler/src/dotty/tools/dotc/CompilationUnit.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ import core.Decorators._
import config.{SourceVersion, Feature}
import StdNames.nme
import scala.annotation.internal.sharable
import scala.util.control.NoStackTrace
import transform.MacroAnnotations

class CompilationUnit protected (val source: SourceFile) {
Expand Down Expand Up @@ -105,7 +106,7 @@ class CompilationUnit protected (val source: SourceFile) {

object CompilationUnit {

class SuspendException extends Exception
class SuspendException extends Exception with NoStackTrace

/** Make a compilation unit for top class `clsd` with the contents of the `unpickled` tree */
def apply(clsd: ClassDenotation, unpickled: Tree, forceTrees: Boolean)(using Context): CompilationUnit =
Expand Down
16 changes: 14 additions & 2 deletions compiler/src/dotty/tools/dotc/core/TypeErrors.scala
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Expand Up @@ -12,10 +12,22 @@ import Denotations._
import Decorators._
import reporting._
import ast.untpd
import config.Printers.cyclicErrors
import config.Printers.{cyclicErrors, noPrinter}

import scala.annotation.constructorOnly

abstract class TypeError(using creationContext: Context) extends Exception(""):

/** Will the stack trace of this exception be filled in?
* This is expensive and only useful for debugging purposes.
*/
def computeStackTrace: Boolean =
ctx.debug || (cyclicErrors != noPrinter && this.isInstanceOf[CyclicReference] && !(ctx.mode is Mode.CheckCyclic))

override def fillInStackTrace(): Throwable =
if computeStackTrace then super.fillInStackTrace().nn
else this

/** Convert to message. This takes an additional Context, so that we
* use the context when the message is first produced, i.e. when the TypeError
* is handled. This makes a difference for CyclicErrors since we need to know
Expand Down Expand Up @@ -164,7 +176,7 @@ class CyclicReference private (val denot: SymDenotation)(using Context) extends
object CyclicReference:
def apply(denot: SymDenotation)(using Context): CyclicReference =
val ex = new CyclicReference(denot)
if !(ctx.mode is Mode.CheckCyclic) || ctx.settings.Ydebug.value then
if ex.computeStackTrace then
cyclicErrors.println(s"Cyclic reference involving! $denot")
val sts = ex.getStackTrace.asInstanceOf[Array[StackTraceElement]]
for (elem <- sts take 200)
Expand Down