[borrow-expr] Add support for borrow expr.

Author: gottesmm

Sources/SwiftParser/Expressions.swift

@@ -465,6 +465,20 @@ extension Parser {
           arena: self.arena
         )
       )
+    case (._borrowContextualKeyword, let handle)?:
+      let borrowTok = self.eat(handle)
+      let sub = self.parseSequenceExpressionElement(
+        flavor,
+        forDirective: forDirective,
+        pattern: pattern
+      )
+      return RawExprSyntax(
+        RawBorrowExprSyntax(
+          borrowKeyword: borrowTok,
+          expression: sub,
+          arena: self.arena
+        )
+      )
     case nil:
       return self.parseUnaryExpression(flavor, forDirective: forDirective, pattern: pattern)
     }

Sources/SwiftParser/RawTokenKindSubset.swift

@@ -583,13 +583,15 @@ public enum TypeSpecifier: RawTokenKindSubset {
 enum AwaitTryMove: RawTokenKindSubset {
   case awaitContextualKeyword
   case _moveContextualKeyword
+  case _borrowContextualKeyword
   case tryKeyword
 
   init?(lexeme: Lexer.Lexeme) {
     switch (lexeme.tokenKind, lexeme.tokenText) {
     case (.tryKeyword, _): self = .tryKeyword
     case (.identifier, "await"): self = .awaitContextualKeyword
     case (.identifier, "_move"): self = ._moveContextualKeyword
+    case (.identifier, "_borrow"): self = ._borrowContextualKeyword
     default: return nil
     }
   }
@@ -598,6 +600,7 @@ enum AwaitTryMove: RawTokenKindSubset {
     switch self {
     case .awaitContextualKeyword: return .identifier
     case ._moveContextualKeyword: return .identifier
+    case ._borrowContextualKeyword: return .identifier
     case .tryKeyword: return .tryKeyword
     }
   }
@@ -606,6 +609,7 @@ enum AwaitTryMove: RawTokenKindSubset {
     switch self {
     case .awaitContextualKeyword: return "await"
     case ._moveContextualKeyword: return "_move"
+    case ._borrowContextualKeyword: return "_borrow"
     default: return nil
     }
   }

Tests/SwiftParserTest/ExpressionTests.swift

@@ -727,6 +727,13 @@ final class ExpressionTests: XCTestCase {
     AssertParse("let b = (_move self).buffer")
   }
 
+  func testMoveExpression() {
+    AssertParse("_borrow msg")
+    AssertParse("use(_borrow msg)")
+    AssertParse("_borrow msg")
+    AssertParse("let b = (_borrow self).buffer")
+  }
+
   func testCodeCompletionExpressions() {
     AssertParse("if !<#b1#> && !<#b2#> {}")
     AssertParse("if <#test#> {}")

Tests/SwiftParserTest/translated/BorrowExprTests.swift

@@ -0,0 +1,43 @@
+d//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+// This test file has been translated from swift/test/Parse/borrow_expr.swift
+
+import XCTest
+
+final class BorrowExprTests: XCTestCase {
+  func testBorrowExpr1() {
+    AssertParse(
+      """
+      func useString(_ str: String) {}
+      var global: String = "123"
+      func testGlobal() {
+        useString(_borrow global)
+      }
+      """
+    )
+  }
+
+  func testBorrowExpr2() {
+    AssertParse(
+      """
+      func useString(_ str: String) {}
+      func testVar() {
+          var t = String()
+          t = String()
+          useString(_borrow t)
+      }
+      """
+    )
+  }
+
+}

gyb_syntax_support/ExprNodes.py

@@ -62,6 +62,14 @@
              Child('Expression', kind='Expr'),
          ]),
 
+    # The borow expr
+    Node('BorrowExpr', name_for_diagnostics="'_borrow' expression", kind='Expr',
+         children=[
+             Child('BorrowKeyword', kind='ContextualKeywordToken',
+                   text_choices=['_borrow']),
+             Child('Expression', kind='Expr'),
+         ]),
+
     # declname-arguments -> '(' declname-argument-list ')'
     # declname-argument-list -> declname-argument*
     # declname-argument -> identifier ':'