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, 12 insertions, 14 deletions

diff --git a/compiler/rustc_errors/src/json/tests.rs b/compiler/rustc_errors/src/json/tests.rs
index 7eb6a4975fe..d940d14e1db 100644
--- a/compiler/rustc_errors/src/json/tests.rs
+++ b/compiler/rustc_errors/src/json/tests.rs
@@ -5,12 +5,18 @@ use rustc_span::source_map::{FilePathMapping, SourceMap};
 
 use crate::emitter::{ColorConfig, HumanReadableErrorType};
 use crate::Handler;
-use rustc_serialize::json;
 use rustc_span::{BytePos, Span};
 
 use std::str;
 
-#[derive(Debug, PartialEq, Eq)]
+use serde::Deserialize;
+
+#[derive(Deserialize, Debug, PartialEq, Eq)]
+struct TestData {
+    spans: Vec<SpanTestData>,
+}
+
+#[derive(Deserialize, Debug, PartialEq, Eq)]
 struct SpanTestData {
     pub byte_start: u32,
     pub byte_end: u32,
@@ -61,19 +67,11 @@ fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
 
         let bytes = output.lock().unwrap();
         let actual_output = str::from_utf8(&bytes).unwrap();
-        let actual_output = json::from_str(&actual_output).unwrap();
-        let spans = actual_output["spans"].as_array().unwrap();
+        let actual_output: TestData = serde_json::from_str(actual_output).unwrap();
+        let spans = actual_output.spans;
         assert_eq!(spans.len(), 1);
-        let obj = &spans[0];
-        let actual_output = SpanTestData {
-            byte_start: obj["byte_start"].as_u64().unwrap() as u32,
-            byte_end: obj["byte_end"].as_u64().unwrap() as u32,
-            line_start: obj["line_start"].as_u64().unwrap() as u32,
-            line_end: obj["line_end"].as_u64().unwrap() as u32,
-            column_start: obj["column_start"].as_u64().unwrap() as u32,
-            column_end: obj["column_end"].as_u64().unwrap() as u32,
-        };
-        assert_eq!(expected_output, actual_output);
+
+        assert_eq!(expected_output, spans[0])
     })
 }