From a0c9bc7167891d7522270f19b971b3a25d7ed807 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 31 Oct 2020 14:37:14 -0700
Subject: [PATCH] Decouple Error from Str::Repr

It was misleading to use Str (which ordinarily represents borrowed
strings) also for owned error messages.
---
 gen/src/write.rs | 25 ++++++++++++++++++++++---
 include/cxx.h    |  6 ++++--
 src/cxx.cc       | 15 +++++++--------
 3 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/gen/src/write.rs b/gen/src/write.rs
index 25f1b0b6..8de422d9 100644
--- a/gen/src/write.rs
+++ b/gen/src/write.rs
@@ -315,6 +315,25 @@ fn write_include_cxxbridge(out: &mut OutFile, apis: &[Api]) {
         writeln!(out, "}};");
     }
 
+    if needs_rust_error {
+        out.begin_block("namespace repr");
+        writeln!(out, "struct PtrLen final {{");
+        writeln!(out, "  const char *ptr;");
+        writeln!(out, "  size_t len;");
+        writeln!(out, "}};");
+        out.end_block("namespace repr");
+
+        writeln!(out, "class impl final {{");
+        writeln!(out, "public:");
+        writeln!(out, "  static Error error(repr::PtrLen ptrlen) noexcept {{");
+        writeln!(out, "    Error error;");
+        writeln!(out, "    error.msg = ptrlen.ptr;");
+        writeln!(out, "    error.len = ptrlen.len;");
+        writeln!(out, "    return error;");
+        writeln!(out, "  }}");
+        writeln!(out, "}};");
+    }
+
     out.end_block("namespace cxxbridge05");
 
     if needs_trycatch {
@@ -685,7 +704,7 @@ fn write_rust_function_decl_impl(
     indirect_call: bool,
 ) {
     if sig.throws {
-        write!(out, "::rust::Str::Repr ");
+        write!(out, "::rust::repr::PtrLen ");
     } else {
         write_extern_return_type_space(out, &sig.ret);
     }
@@ -823,7 +842,7 @@ fn write_rust_function_shim_impl(
         }
     }
     if sig.throws {
-        write!(out, "::rust::Str::Repr error$ = ");
+        write!(out, "::rust::repr::PtrLen error$ = ");
     }
     write!(out, "{}(", invoke);
     if sig.receiver.is_some() {
@@ -871,7 +890,7 @@ fn write_rust_function_shim_impl(
     writeln!(out, ";");
     if sig.throws {
         writeln!(out, "  if (error$.ptr) {{");
-        writeln!(out, "    throw ::rust::Error(error$);");
+        writeln!(out, "    throw ::rust::impl::error(error$);");
         writeln!(out, "  }}");
     }
     if indirect_return {
diff --git a/include/cxx.h b/include/cxx.h
index bf16dd05..d044111b 100644
--- a/include/cxx.h
+++ b/include/cxx.h
@@ -251,12 +251,14 @@ class Error final : public std::exception {
 public:
   Error(const Error &);
   Error(Error &&) noexcept;
-  Error(Str::Repr) noexcept;
   ~Error() noexcept;
   const char *what() const noexcept override;
 
 private:
-  Str::Repr msg;
+  Error() noexcept = default;
+  friend class impl;
+  const char *msg;
+  size_t len;
 };
 #endif // CXXBRIDGE05_RUST_ERROR
 
diff --git a/src/cxx.cc b/src/cxx.cc
index 43bf245b..077f8ced 100644
--- a/src/cxx.cc
+++ b/src/cxx.cc
@@ -172,22 +172,21 @@ const char *cxxbridge05$error(const char *ptr, size_t len) {
 }
 } // extern "C"
 
-Error::Error(Str::Repr msg) noexcept : msg(msg) {}
-
 Error::Error(const Error &other) {
-  this->msg.ptr = cxxbridge05$error(other.msg.ptr, other.msg.len);
-  this->msg.len = other.msg.len;
+  this->msg = cxxbridge05$error(other.msg, other.len);
+  this->len = other.len;
 }
 
 Error::Error(Error &&other) noexcept {
   this->msg = other.msg;
-  other.msg.ptr = nullptr;
-  other.msg.len = 0;
+  this->len = other.len;
+  other.msg = nullptr;
+  other.len = 0;
 }
 
-Error::~Error() noexcept { delete[] this->msg.ptr; }
+Error::~Error() noexcept { delete[] this->msg; }
 
-const char *Error::what() const noexcept { return this->msg.ptr; }
+const char *Error::what() const noexcept { return this->msg; }
 
 } // namespace cxxbridge05
 } // namespace rust