[stdlib] [gardening] Remove whitespace, document growth issue

Author: milseman

stdlib/public/core/StringGutsRangeReplaceable.swift

@@ -58,7 +58,7 @@ extension _StringGuts {
   internal init(_initialCapacity capacity: Int) {
     self.init()
     if _slowPath(capacity > _SmallString.capacity) {
-      self.grow(capacity)
+      self.grow(capacity) // TODO: no factor should be applied
     }
   }
 
@@ -68,7 +68,7 @@ extension _StringGuts {
     if let currentCap = self.uniqueNativeCapacity, currentCap >= n { return }
 
     // Grow
-    self.grow(n)
+    self.grow(n) // TODO: no factor should be applied
   }
 
   // Grow to accomodate at least `n` code units
@@ -128,11 +128,11 @@ extension _StringGuts {
     } else {
       sufficientCapacity = false
     }
-        
+
     if self.isUniqueNative && sufficientCapacity {
       return
     }
-    
+
     // If we have to resize anyway, and we fit in smol, we should have made one
     _internalInvariant(totalCount > _SmallString.capacity)
 
@@ -145,7 +145,7 @@ extension _StringGuts {
       growthTarget = Swift.max(
         totalCount, _growArrayCapacity(nativeCapacity ?? 0))
     }
-    self.grow(growthTarget)
+    self.grow(growthTarget) // NOTE: this already has exponential growth...
   }
 
   internal mutating func append(_ other: _StringGuts) {
@@ -157,7 +157,7 @@ extension _StringGuts {
     }
     append(_StringGutsSlice(other))
   }
-  
+
   @inline(never)
   @_effects(readonly)
   private func _foreignConvertedToSmall() -> _SmallString {
@@ -170,7 +170,7 @@ extension _StringGuts {
     _internalInvariant(smol._guts.isSmall)
     return smol._guts.asSmall
   }
-  
+
   private func _convertedToSmall() -> _SmallString {
     _internalInvariant(utf8Count <= _SmallString.capacity)
     if _fastPath(isSmall) {
@@ -186,25 +186,25 @@ extension _StringGuts {
     defer { self._invariantCheck() }
 
     let otherCount = slicedOther.utf8Count
-    
+
     let totalCount = utf8Count + otherCount
-    
+
     /*
      Goal: determine if we need to allocate new native capacity
      Possible scenarios in which we need to allocate:
      • Not uniquely owned and native: we can't use the capacity to grow into,
         have to become unique + native by allocating
      • Not enough capacity: have to allocate to grow
-     
+
      Special case: a non-smol String that can fit in a smol String but doesn't
         meet the above criteria shouldn't throw away its buffer just to be smol.
         The reasoning here is that it may be bridged or have reserveCapacity'd
         in preparation for appending more later, in which case we would end up
         have to allocate anyway to convert back from smol.
-     
+
         If we would have to re-allocate anyway then that's not a problem and we
         should just be smol.
-     
+
         e.g. consider
         var str = "" // smol
         str.reserveCapacity(100) // large native unique
@@ -215,15 +215,15 @@ extension _StringGuts {
       nativeUnusedCapacity! >= otherCount
     let shouldBeSmol = totalCount <= _SmallString.capacity &&
       (isSmall || !hasEnoughUsableSpace)
-    
+
     if shouldBeSmol {
       let smolSelf = _convertedToSmall()
       let smolOther = String(Substring(slicedOther))._guts._convertedToSmall()
       // TODO: In-register slicing
       self = _StringGuts(_SmallString(smolSelf, appending: smolOther)!)
       return
     }
-    
+
     prepareForAppendInPlace(totalCount: totalCount, otherUTF8Count: otherCount)
 
     if slicedOther.isFastUTF8 {