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Avoid creating unnecessary strings in adjustExtension #9598

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Merged
merged 2 commits into from
Aug 20, 2020
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Avoid creating unnecessary strings in adjustExtension #9598

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a09e4b2
Avoid creating unnecessary strings in adjustExtension
odersky Jul 23, 2020
7e45458
Rename parameter for clarity
odersky Aug 20, 2020
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16 changes: 11 additions & 5 deletions compiler/src/dotty/tools/dotc/core/Names.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -146,7 +146,9 @@ object Names {
def startsWith(str: String, start: Int = 0): Boolean = firstPart.startsWith(str, start)

/** Does (the last part of) this name end with `str`? */
def endsWith(str: String): Boolean = lastPart.endsWith(str)
def endsWith(suffix: String): Boolean = lastPart.endsWith(suffix)

def endsWith(suffix: SimpleName): Boolean = lastPart.endsWith(suffix)

override def hashCode: Int = System.identityHashCode(this)
override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
Expand Down Expand Up @@ -363,11 +365,15 @@ object Names {
i == str.length
}

override def endsWith(str: String): Boolean = {
override def endsWith(suffix: String): Boolean =
var i = 1
while (i <= str.length && i <= length && apply(length - i) == str(str.length - i)) i += 1
i > str.length
}
while i <= suffix.length && i <= length && apply(length - i) == suffix(suffix.length - i) do i += 1
i > suffix.length

override def endsWith(suffix: SimpleName): Boolean =
var i = 1
while i <= suffix.length && i <= length && apply(length - i) == suffix(suffix.length - i) do i += 1
i > suffix.length

override def replace(from: Char, to: Char): SimpleName = {
val cs = new Array[Char](length)
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7 changes: 5 additions & 2 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Expand Up @@ -215,8 +215,11 @@ class Typer extends Namer
def namedImportRef(imp: ImportInfo)(using Context): Type = {
val termName = name.toTermName

def adjustExtension(name: Name) =
if required.is(ExtensionMethod) then name.toExtensionName else name
def adjustExtension(n: Name) =
if required.is(ExtensionMethod) && termName.endsWith(n.lastPart)
// pre-check to avoid forming a new string; form extension only if it has a chance of matching `termName`
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Will termName.endsWith(name.lastPart) be always true, given that termName = name.toTermName?

then n.toExtensionName
else n

def recur(selectors: List[untpd.ImportSelector]): Type = selectors match
case selector :: rest =>
Expand Down