SIL: allow inserting specific instruction classes into an InstructionSet

Instead, remove `Operand.users(ofType:)` which returned a sequence of `Instruction` - which was a kind of replacement for the missing `InstructionSet` API

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/DataStructures/Set.swift

@@ -268,6 +268,14 @@ struct OperandSet : IntrusiveSet {
   }
 }
 
+extension InstructionSet {
+  mutating func insert<I: Instruction>(contentsOf source: some Sequence<I>) {
+    for inst in source {
+      _ = insert(inst)
+    }
+  }
+}
+
 extension IntrusiveSet {
   mutating func insert(contentsOf source: some Sequence<Element>) {
     for element in source {

SwiftCompilerSources/Sources/SIL/Instruction.swift

@@ -1366,7 +1366,7 @@ final public class AllocStackInst : SingleValueInstruction, Allocation, DebugVar
     return bridged.AllocStack_hasVarInfo() ? bridged.AllocStack_getVarInfo() : nil
   }
 
-  public var deallocations: LazyMapSequence<LazyFilterSequence<UseList>, Instruction> {
+  public var deallocations: LazyMapSequence<LazyFilterSequence<UseList>, DeallocStackInst> {
     uses.users(ofType: DeallocStackInst.self)
   }
 }
@@ -1484,7 +1484,7 @@ final public class StoreBorrowInst : SingleValueInstruction, StoringInstruction,
     return self.uses.lazy.filter { $0.instruction is EndBorrowInst }
   }
 
-  public var endBorrows: LazyMapSequence<LazyFilterSequence<UseList>, Instruction> {
+  public var endBorrows: LazyMapSequence<LazyFilterSequence<UseList>, EndBorrowInst> {
     // A `store_borrow` is an address value.
     // Only `end_borrow`s (with this address operand) can end such a borrow scope.
     uses.users(ofType: EndBorrowInst.self)

SwiftCompilerSources/Sources/SIL/Operand.swift

@@ -185,12 +185,6 @@ extension Sequence where Element == Operand {
   public func users<I: Instruction>(ofType: I.Type) -> LazyMapSequence<LazyFilterSequence<Self>, I> {
     self.lazy.filter{ $0.instruction is I }.lazy.map { $0.instruction as! I }
   }
-
-  // This overload which returns a Sequence of `Instruction` and not a Sequence of `I` is used for APIs, like
-  // `InstructionSet.insert(contentsOf:)`, which require a sequence of `Instruction`.
-  public func users<I: Instruction>(ofType: I.Type) -> LazyMapSequence<LazyFilterSequence<Self>, Instruction> {
-    self.lazy.filter{ $0.instruction is I }.users
-  }
 }
 
 extension Value {