Merge pull request #80090 from swiftlang/egorzhdan/std-string-interpolation

[cxx-interop] Conform `std::string` to `ExpressibleByStringInterpolation`

Author: egorzhdan

stdlib/public/Cxx/std/String.swift

@@ -82,21 +82,27 @@ extension std.u32string {
 
 // MARK: Initializing C++ string from a Swift String literal
 
-extension std.string: ExpressibleByStringLiteral {
+extension std.string: ExpressibleByStringLiteral,
+  ExpressibleByStringInterpolation {
+
   @_alwaysEmitIntoClient
   public init(stringLiteral value: String) {
     unsafe self.init(value)
   }
 }
 
-extension std.u16string: ExpressibleByStringLiteral {
+extension std.u16string: ExpressibleByStringLiteral,
+  ExpressibleByStringInterpolation {
+
   @_alwaysEmitIntoClient
   public init(stringLiteral value: String) {
     unsafe self.init(value)
   }
 }
 
-extension std.u32string: ExpressibleByStringLiteral {
+extension std.u32string: ExpressibleByStringLiteral,
+  ExpressibleByStringInterpolation {
+
   @_alwaysEmitIntoClient
   public init(stringLiteral value: String) {
     unsafe self.init(value)

test/Interop/Cxx/stdlib/use-std-string-typechecker.swift

@@ -4,3 +4,6 @@ import CxxStdlib
 import StdString
 
 let _ = HasMethodThatReturnsString().getString()
+
+let x: std.string = "Hello"
+let y: std.string = "\(x), World!" 

test/Interop/Cxx/stdlib/use-std-string.swift

@@ -65,6 +65,12 @@ StdStringTestSuite.test("std::string <=> Swift.String") {
     }
     let swift7 = String(cxx7)
     expectEqual(swift7, "���")
+
+    let cxxLiteral: std.string = "Hello"
+    let cxx8: std.string = "\(cxxLiteral), World!"
+    expectEqual(cxx8.size(), 13)
+    let swift8 = String(cxx8)
+    expectEqual(swift8, "Hello, World!")
 }
 
 StdStringTestSuite.test("std::string operators") {
@@ -287,6 +293,12 @@ StdStringTestSuite.test("std::u16string <=> Swift.String") {
     expectEqual(cxx6.size(), 7)
     let swift6 = String(cxx6)
     expectEqual(swift6, "xyz\0abc")
+
+    let cxxLiteral: std.u16string = "Hello"
+    let cxx8: std.u16string = "\(cxxLiteral), World!"
+    expectEqual(cxx8.size(), 13)
+    let swift8 = String(cxx8)
+    expectEqual(swift8, "Hello, World!")
 }
 
 StdStringTestSuite.test("std::u32string <=> Swift.String") {
@@ -317,6 +329,12 @@ StdStringTestSuite.test("std::u32string <=> Swift.String") {
     expectEqual(cxx6.size(), 7)
     let swift6 = String(cxx6)
     expectEqual(swift6, "xyz\0abc")
+
+    let cxxLiteral: std.u32string = "Hello"
+    let cxx8: std.u32string = "\(cxxLiteral), World!"
+    expectEqual(cxx8.size(), 13)
+    let swift8 = String(cxx8)
+    expectEqual(swift8, "Hello, World!")
 }
 
 StdStringTestSuite.test("std::string as Swift.CustomDebugStringConvertible") {