Make InstructionTranslator non-copyable

This avoids unintentional possible ARC traffic if `InstructionTranslator` is accidentally copied, as it stores references to classes like `ISeqAllocator`.

Author: MaxDesiatov

Sources/WasmKit/Execution/Function.swift

@@ -253,19 +253,18 @@ struct WasmFunctionEntity {
         let store = store.value
         let engine = store.engine
         let type = self.type
-        var translator = try InstructionTranslator(
-            allocator: store.allocator.iseqAllocator,
-            engineConfiguration: engine.configuration,
-            funcTypeInterner: engine.funcTypeInterner,
-            module: instance,
-            type: engine.resolveType(type),
-            locals: code.locals,
-            functionIndex: index,
-            codeSize: code.expression.count,
-            isIntercepting: engine.interceptor != nil
-        )
         let iseq = try code.withValue { code in
-            try translator.translate(code: code)
+            try InstructionTranslator(
+                allocator: store.allocator.iseqAllocator,
+                engineConfiguration: engine.configuration,
+                funcTypeInterner: engine.funcTypeInterner,
+                module: instance,
+                type: engine.resolveType(type),
+                locals: code.locals,
+                functionIndex: index,
+                codeSize: code.expression.count,
+                isIntercepting: engine.interceptor != nil
+            ).translate(code: code)
         }
         self.code = .compiled(iseq)
         return iseq

Sources/WasmKit/Translator.swift

@@ -293,7 +293,7 @@ struct StackLayout {
     }
 }
 
-struct InstructionTranslator: InstructionVisitor {
+struct InstructionTranslator: ~Copyable, InstructionVisitor {
     typealias Output = Void
 
     typealias LabelRef = Int
@@ -526,15 +526,15 @@ struct InstructionTranslator: InstructionVisitor {
         }
     }
 
-    fileprivate struct ISeqBuilder {
+    fileprivate struct ISeqBuilder: ~Copyable {
         typealias InstructionFactoryWithLabel = (
-            ISeqBuilder,
+            borrowing ISeqBuilder,
             // The position of the next slot of the creating instruction
             _ source: MetaProgramCounter,
             // The position of the resolved label
             _ target: MetaProgramCounter
         ) -> (WasmKit.Instruction)
-        typealias BrTableEntryFactory = (ISeqBuilder, MetaProgramCounter) -> Instruction.BrTableOperand.Entry
+        typealias BrTableEntryFactory = (borrowing ISeqBuilder, MetaProgramCounter) -> Instruction.BrTableOperand.Entry
         typealias BuildingBrTable = UnsafeMutableBufferPointer<Instruction.BrTableOperand.Entry>
 
         enum OnPinAction {
@@ -639,7 +639,7 @@ struct InstructionTranslator: InstructionVisitor {
             }
         }
 
-        func finalize() -> [UInt64] {
+        consuming func finalize() -> [UInt64] {
             return instructions
         }
 
@@ -707,7 +707,7 @@ struct InstructionTranslator: InstructionVisitor {
             line: UInt = #line,
             make:
                 @escaping (
-                    ISeqBuilder,
+                    borrowing ISeqBuilder,
                     // The position of the next slot of the creating instruction
                     _ source: MetaProgramCounter,
                     // The position of the resolved label
@@ -1077,7 +1077,7 @@ struct InstructionTranslator: InstructionVisitor {
         try valueStack.truncate(height: currentFrame.stackHeight)
     }
 
-    private mutating func finalize() throws -> InstructionSequence {
+    private consuming func finalize() throws -> InstructionSequence {
         if controlStack.numberOfFrames > 1 {
             throw ValidationError(.expectedMoreEndInstructions(count: controlStack.numberOfFrames - 1))
         }
@@ -1102,7 +1102,7 @@ struct InstructionTranslator: InstructionVisitor {
     // MARK: Main entry point
 
     /// Translate a Wasm expression into a sequence of instructions.
-    mutating func translate(code: Code) throws -> InstructionSequence {
+    consuming func translate(code: Code) throws -> InstructionSequence {
         if isIntercepting {
             // Emit `onEnter` instruction at the beginning of the function
             emit(.onEnter(functionIndex))

Sources/WasmParser/BinaryInstructionDecoder.swift

@@ -90,7 +90,7 @@ protocol BinaryInstructionDecoder {
 }
 
 @inlinable
-func parseBinaryInstruction(visitor: inout some InstructionVisitor, decoder: inout some BinaryInstructionDecoder) throws -> Bool {
+func parseBinaryInstruction(visitor: inout some InstructionVisitor & ~Copyable, decoder: inout some BinaryInstructionDecoder) throws -> Bool {
     let opcode0 = try decoder.claimNextByte()
     switch opcode0 {
     case 0x00:

Sources/WasmParser/InstructionVisitor.swift

@@ -309,7 +309,7 @@ extension AnyInstructionVisitor {
 ///
 /// The visitor pattern is used while parsing WebAssembly expressions to allow for easy extensibility.
 /// See the expression parsing method ``Code/parseExpression(visitor:)``
-public protocol InstructionVisitor {
+public protocol InstructionVisitor: ~Copyable {
     /// Visiting `unreachable` instruction.
     mutating func visitUnreachable() throws
     /// Visiting `nop` instruction.
@@ -482,7 +482,7 @@ extension InstructionVisitor {
 }
 
 // MARK: - Placeholder implementations
-extension InstructionVisitor {
+extension InstructionVisitor where Self: ~Copyable {
     public mutating func visitUnreachable() throws {}
     public mutating func visitNop() throws {}
     public mutating func visitBlock(blockType: BlockType) throws {}

Sources/WasmParser/WasmParser.swift

@@ -160,7 +160,7 @@ public struct ExpressionParser {
     }
 
     @inlinable
-    public mutating func visit<V: InstructionVisitor>(visitor: inout V) throws -> Bool {
+    public mutating func visit(visitor: inout some InstructionVisitor & ~Copyable) throws -> Bool {
         isLastEnd = try parser.parseInstruction(visitor: &visitor)
         let shouldContinue = try !parser.stream.hasReachedEnd()
         if !shouldContinue {
@@ -751,7 +751,7 @@ extension Parser: BinaryInstructionDecoder {
     /// Returns: `true` if the parsed instruction is the block end instruction.
     @inline(__always)
     @inlinable
-    mutating func parseInstruction<V: InstructionVisitor>(visitor v: inout V) throws -> Bool {
+    mutating func parseInstruction(visitor v: inout some InstructionVisitor & ~Copyable) throws -> Bool {
         return try parseBinaryInstruction(visitor: &v, decoder: &self)
     }