Auto merge of #85993 - bjorn3:serde_json, r=wesleywiser

Remove all json handling from rustc_serialize

Json is now handled using serde_json. Where appropriate I have replaced json usage with binary serialization (rmeta files) or manual string formatting (emcc linker arg generation).

This allowed for removing and simplifying a lot of code, which hopefully results in faster serialization/deserialization and faster compiles of rustc itself.

Where sensible we now use serde. Metadata and incr cache serialization keeps using a heavily modified (compared to crates.io) rustc-serialize version that in the future could probably be extended with zero-copy deserialization or other perf tricks that serde can't support due to supporting more than one serialization format.

Note that I had to remove `-Zast-json` and `-Zast-json-noexpand` as the relevant AST types don't implement `serde::Serialize`.

Fixes #40177

See also https://github.com/rust-lang/compiler-team/issues/418

1 files changed, 6 insertions, 7 deletions

diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index 904d6f8cfd8..179a184536e 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -30,7 +30,6 @@ use rustc_log::stdout_isatty;
 use rustc_metadata::locator;
 use rustc_save_analysis as save;
 use rustc_save_analysis::DumpHandler;
-use rustc_serialize::json::ToJson;
 use rustc_session::config::{nightly_options, CG_OPTIONS, DB_OPTIONS};
 use rustc_session::config::{ErrorOutputType, Input, OutputType, PrintRequest, TrimmedDefPaths};
 use rustc_session::cstore::MetadataLoader;
@@ -40,6 +39,7 @@ use rustc_session::{config, DiagnosticOutput, Session};
 use rustc_session::{early_error, early_error_no_abort, early_warn};
 use rustc_span::source_map::{FileLoader, FileName};
 use rustc_span::symbol::sym;
+use rustc_target::json::ToJson;
 
 use std::borrow::Cow;
 use std::cmp::max;
@@ -343,10 +343,7 @@ fn run_compiler(
                 return early_exit();
             }
 
-            if sess.opts.debugging_opts.parse_only
-                || sess.opts.debugging_opts.show_span.is_some()
-                || sess.opts.debugging_opts.ast_json_noexpand
-            {
+            if sess.opts.debugging_opts.parse_only || sess.opts.debugging_opts.show_span.is_some() {
                 return early_exit();
             }
 
@@ -375,7 +372,7 @@ fn run_compiler(
 
             queries.global_ctxt()?;
 
-            if sess.opts.debugging_opts.no_analysis || sess.opts.debugging_opts.ast_json {
+            if sess.opts.debugging_opts.no_analysis {
                 return early_exit();
             }
 
@@ -665,7 +662,9 @@ fn print_crate_info(
             }
             Sysroot => println!("{}", sess.sysroot.display()),
             TargetLibdir => println!("{}", sess.target_tlib_path.dir.display()),
-            TargetSpec => println!("{}", sess.target.to_json().pretty()),
+            TargetSpec => {
+                println!("{}", serde_json::to_string_pretty(&sess.target.to_json()).unwrap());
+            }
             FileNames | CrateName => {
                 let input = input.unwrap_or_else(|| {
                     early_error(ErrorOutputType::default(), "no input file provided")