From 722f543b58837621ba731e10dfbf1a7d2804431a Mon Sep 17 00:00:00 2001
From: Justus Adam <dev@justus.science>
Date: Wed, 6 Sep 2023 15:47:36 -0700
Subject: [PATCH] A much simpler way to set the sysroot. (#34)

## What Changed?

Reimplements #32 in a simpler manner. Partially reverts those changes
but with the same overall outcome.

Also added documentation for what is happening.

## Why Does It Need To?

The other version to achieve this needed more changes to `rustc_plugin`
that were haphazard and would have been annoying to try and get merged
eventually. This way is slightly more hacky but with a *significantly*
reduced footprint. Everything is now contained in `dfpp` alone.

## Checklist

- [x] Above description has been filled out so that upon quash merge we
have a
  good record of what changed.
- [x] New functions, methods, types are documented. Old documentation is
updated
  if necessary
- [x] Documentation in Notion has been updated
- [x] Tests for new behaviors are provided
  - [x] New test suites (if any) ave been added to the CI tests (in
`.github/workflows/rust.yml`) either as compiler test or integration
test.
*Or* justification for their omission from CI has been provided in this
PR
    description.
---
 Cargo.lock |  8 ++++----
 Cargo.toml |  4 ++--
 src/lib.rs | 11 ++++++++++-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index a699613bb9..cfcf06d9a0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -901,12 +901,12 @@ name = "rustc_plugin"
 version = "0.6.0-nightly-2023-04-12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "79b172d929863ef84797b5592af9b58160f954a484938991f5a6b2829e3c163a"
-replace = "rustc_plugin 0.6.0-nightly-2023-04-12 (git+https://github.com/JustusAdam/rustc_plugin?rev=a50617487e129623df946c42d554bd8080765096)"
+replace = "rustc_plugin 0.6.0-nightly-2023-04-12 (git+https://github.com/JustusAdam/rustc_plugin?rev=344ecb3bc056c641eaf9d06792571b3d81c8eb33)"
 
 [[package]]
 name = "rustc_plugin"
 version = "0.6.0-nightly-2023-04-12"
-source = "git+https://github.com/JustusAdam/rustc_plugin?rev=a50617487e129623df946c42d554bd8080765096#a50617487e129623df946c42d554bd8080765096"
+source = "git+https://github.com/JustusAdam/rustc_plugin?rev=344ecb3bc056c641eaf9d06792571b3d81c8eb33#344ecb3bc056c641eaf9d06792571b3d81c8eb33"
 dependencies = [
  "cargo_metadata",
  "log",
@@ -927,12 +927,12 @@ name = "rustc_utils"
 version = "0.6.0-nightly-2023-04-12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3935b4a82abe6904308c9273afba6160cf36f20044e720c43839a08519eadfd8"
-replace = "rustc_utils 0.6.0-nightly-2023-04-12 (git+https://github.com/JustusAdam/rustc_plugin?rev=a50617487e129623df946c42d554bd8080765096)"
+replace = "rustc_utils 0.6.0-nightly-2023-04-12 (git+https://github.com/JustusAdam/rustc_plugin?rev=344ecb3bc056c641eaf9d06792571b3d81c8eb33)"
 
 [[package]]
 name = "rustc_utils"
 version = "0.6.0-nightly-2023-04-12"
-source = "git+https://github.com/JustusAdam/rustc_plugin?rev=a50617487e129623df946c42d554bd8080765096#a50617487e129623df946c42d554bd8080765096"
+source = "git+https://github.com/JustusAdam/rustc_plugin?rev=344ecb3bc056c641eaf9d06792571b3d81c8eb33#344ecb3bc056c641eaf9d06792571b3d81c8eb33"
 dependencies = [
  "anyhow",
  "cfg-if",
diff --git a/Cargo.toml b/Cargo.toml
index bb77517368..4c8b3ab2dd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -69,5 +69,5 @@ debug = true
 
 [replace]
 
-"rustc_utils:0.6.0-nightly-2023-04-12" = { git = "https://github.com/JustusAdam/rustc_plugin", rev = "a50617487e129623df946c42d554bd8080765096" }
-"rustc_plugin:0.6.0-nightly-2023-04-12" = { git = "https://github.com/JustusAdam/rustc_plugin", rev = "a50617487e129623df946c42d554bd8080765096" }
\ No newline at end of file
+"rustc_utils:0.6.0-nightly-2023-04-12" = { git = "https://github.com/JustusAdam/rustc_plugin", rev = "344ecb3bc056c641eaf9d06792571b3d81c8eb33" }
+"rustc_plugin:0.6.0-nightly-2023-04-12" = { git = "https://github.com/JustusAdam/rustc_plugin", rev = "344ecb3bc056c641eaf9d06792571b3d81c8eb33" }
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 860b820701..95e2673d52 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -227,10 +227,19 @@ impl rustc_plugin::RustcPlugin for DfppPlugin {
     ) -> rustc_plugin::RustcPluginArgs<Self::Args> {
         use clap::Parser;
         let args = ArgWrapper::parse();
+
+        // Override the SYSROOT so that it points to the version we were
+        // compiled against.
+        //
+        // This is actually not necessary for *this* binary, but it will bne
+        // inherited by the calls to `cargo` and `rustc` does by `rustc_plugin`
+        // and thus those will link against the version of `std` that we
+        // require.
+        std::env::set_var("SYSROOT", env!("SYSROOT_PATH"));
+
         rustc_plugin::RustcPluginArgs {
             args: Args::from_parseable(args.args).unwrap(),
             filter: CrateFilter::OnlyWorkspace,
-            env: vec![("SYSROOT".into(), env!("SYSROOT_PATH").into())],
         }
     }