Remove serialization of diagnostics to files

This is no longer used by the index generator and was always an unstable
compiler detail, so strip it out.

This also leaves in RUSTC_ERROR_METADATA_DST since the stage0 compiler
still needs it to be set.

6 files changed, 13 insertions, 132 deletions

diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 36229720e42..4f96c12fc1d 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -825,8 +825,7 @@ impl Step for ErrorIndex {
         index.arg(crate::channel::CFG_RELEASE_NUM);
 
         // FIXME: shouldn't have to pass this env var
-        index.env("CFG_BUILD", &builder.config.build)
-             .env("RUSTC_ERROR_METADATA_DST", builder.extended_error_dir());
+        index.env("CFG_BUILD", &builder.config.build);
 
         builder.run(&mut index);
     }
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index c2c134bfd1d..87bd5cbacff 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1535,8 +1535,7 @@ impl Step for ErrorIndex {
         );
         tool.arg("markdown")
             .arg(&output)
-            .env("CFG_BUILD", &builder.config.build)
-            .env("RUSTC_ERROR_METADATA_DST", builder.extended_error_dir());
+            .env("CFG_BUILD", &builder.config.build);
 
         builder.info(&format!("Testing error-index stage{}", compiler.stage));
         let _time = util::timeit(&builder);
diff --git a/src/libsyntax/diagnostics/metadata.rs b/src/libsyntax/diagnostics/metadata.rs
deleted file mode 100644
index 53f37bb10bd..00000000000
--- a/src/libsyntax/diagnostics/metadata.rs
+++ /dev/null
@@ -1,93 +0,0 @@
-//! This module contains utilities for outputting metadata for diagnostic errors.
-//!
-//! Each set of errors is mapped to a metadata file by a name, which is
-//! currently always a crate name.
-
-use std::collections::BTreeMap;
-use std::env;
-use std::fs::{remove_file, create_dir_all, File};
-use std::io::Write;
-use std::path::PathBuf;
-use std::error::Error;
-use rustc_serialize::json::as_json;
-
-use syntax_pos::{Span, FileName};
-
-use crate::ext::base::ExtCtxt;
-use crate::diagnostics::plugin::{ErrorMap, ErrorInfo};
-
-/// JSON encodable/decodable version of `ErrorInfo`.
-#[derive(PartialEq, RustcDecodable, RustcEncodable)]
-pub struct ErrorMetadata {
-    pub description: Option<String>,
-    pub use_site: Option<ErrorLocation>
-}
-
-/// Mapping from error codes to metadata that can be (de)serialized.
-pub type ErrorMetadataMap = BTreeMap<String, ErrorMetadata>;
-
-/// JSON encodable error location type with filename and line number.
-#[derive(PartialEq, RustcDecodable, RustcEncodable)]
-pub struct ErrorLocation {
-    pub filename: FileName,
-    pub line: usize
-}
-
-impl ErrorLocation {
-    /// Creates an error location from a span.
-    pub fn from_span(ecx: &ExtCtxt<'_>, sp: Span) -> ErrorLocation {
-        let loc = ecx.source_map().lookup_char_pos(sp.lo());
-        ErrorLocation {
-            filename: loc.file.name.clone(),
-            line: loc.line
-        }
-    }
-}
-
-/// Gets the directory where metadata for a given `prefix` should be stored.
-///
-/// See `output_metadata`.
-pub fn get_metadata_dir(prefix: &str) -> PathBuf {
-    env::var_os("RUSTC_ERROR_METADATA_DST")
-        .map(PathBuf::from)
-        .expect("env var `RUSTC_ERROR_METADATA_DST` isn't set")
-        .join(prefix)
-}
-
-/// Map `name` to a path in the given directory: <directory>/<name>.json
-fn get_metadata_path(directory: PathBuf, name: &str) -> PathBuf {
-    directory.join(format!("{}.json", name))
-}
-
-/// Write metadata for the errors in `err_map` to disk, to a file corresponding to `prefix/name`.
-///
-/// For our current purposes the prefix is the target architecture and the name is a crate name.
-/// If an error occurs steps will be taken to ensure that no file is created.
-pub fn output_metadata(ecx: &ExtCtxt<'_>, prefix: &str, name: &str, err_map: &ErrorMap)
-    -> Result<(), Box<dyn Error>>
-{
-    // Create the directory to place the file in.
-    let metadata_dir = get_metadata_dir(prefix);
-    create_dir_all(&metadata_dir)?;
-
-    // Open the metadata file.
-    let metadata_path = get_metadata_path(metadata_dir, name);
-    let mut metadata_file = File::create(&metadata_path)?;
-
-    // Construct a serializable map.
-    let json_map = err_map.iter().map(|(k, &ErrorInfo { description, use_site })| {
-        let key = k.as_str().to_string();
-        let value = ErrorMetadata {
-            description: description.map(|n| n.as_str().to_string()),
-            use_site: use_site.map(|sp| ErrorLocation::from_span(ecx, sp))
-        };
-        (key, value)
-    }).collect::<ErrorMetadataMap>();
-
-    // Write the data to the file, deleting it if the write fails.
-    let result = write!(&mut metadata_file, "{}", as_json(&json_map));
-    if result.is_err() {
-        remove_file(&metadata_path)?;
-    }
-    Ok(result?)
-}
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index 9618b5acfb0..e9a55af52e8 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -1,5 +1,4 @@
 use std::collections::BTreeMap;
-use std::env;
 
 use crate::ast::{self, Ident, Name};
 use crate::source_map;
@@ -12,8 +11,6 @@ use crate::tokenstream::{TokenTree};
 use smallvec::smallvec;
 use syntax_pos::Span;
 
-use crate::diagnostics::metadata::output_metadata;
-
 pub use errors::*;
 
 // Maximum width of any line in an extended error description (inclusive).
@@ -127,36 +124,13 @@ pub fn expand_build_diagnostic_array<'cx>(ecx: &'cx mut ExtCtxt<'_>,
                                           token_tree: &[TokenTree])
                                           -> Box<dyn MacResult+'cx> {
     assert_eq!(token_tree.len(), 3);
-    let (crate_name, ident) = match (&token_tree[0], &token_tree[2]) {
-        (
-            // Crate name.
-            &TokenTree::Token(Token { kind: token::Ident(crate_name, _), .. }),
-            // DIAGNOSTICS ident.
-            &TokenTree::Token(Token { kind: token::Ident(name, _), span })
-        ) => (crate_name, Ident::new(name, span)),
+    let ident = match &token_tree[2] {
+        // DIAGNOSTICS ident.
+        &TokenTree::Token(Token { kind: token::Ident(name, _), span })
+        => Ident::new(name, span),
         _ => unreachable!()
     };
 
-    // Output error metadata to `tmp/extended-errors/<target arch>/<crate name>.json`
-    if let Ok(target_triple) = env::var("CFG_COMPILER_HOST_TRIPLE") {
-        ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
-            if let Err(e) = output_metadata(ecx,
-                                            &target_triple,
-                                            &crate_name.as_str(),
-                                            diagnostics) {
-                ecx.span_bug(span, &format!(
-                    "error writing metadata for triple `{}` and crate `{}`, error: {}, \
-                     cause: {:?}",
-                    target_triple, crate_name, e.description(), e.source()
-                ));
-            }
-        });
-    } else {
-        ecx.span_err(span, &format!(
-            "failed to write metadata for crate `{}` because $CFG_COMPILER_HOST_TRIPLE is not set",
-            crate_name));
-    }
-
     // Construct the output expression.
     let (count, expr) =
         ecx.parse_sess.registered_diagnostics.with_lock(|diagnostics| {
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 8ac48d8d74a..1741932c1b8 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -124,7 +124,6 @@ pub mod diagnostics {
     #[macro_use]
     pub mod macros;
     pub mod plugin;
-    pub mod metadata;
 }
 
 // N.B., this module needs to be declared first so diagnostics are
diff --git a/src/tools/error_index_generator/main.rs b/src/tools/error_index_generator/main.rs
index b35d304e760..c4826a0c31d 100644
--- a/src/tools/error_index_generator/main.rs
+++ b/src/tools/error_index_generator/main.rs
@@ -13,10 +13,16 @@ use std::path::PathBuf;
 use std::cell::RefCell;
 
 use syntax::edition::DEFAULT_EDITION;
-use syntax::diagnostics::metadata::{ErrorMetadataMap, ErrorMetadata};
 
 use rustdoc::html::markdown::{Markdown, IdMap, ErrorCodes, Playground};
 
+pub struct ErrorMetadata {
+    pub description: Option<String>,
+}
+
+/// Mapping from error codes to metadata that can be (de)serialized.
+pub type ErrorMetadataMap = BTreeMap<String, ErrorMetadata>;
+
 enum OutputFormat {
     HTML(HTMLFormatter),
     Markdown(MarkdownFormatter),
@@ -214,9 +220,6 @@ fn main_with_result(format: OutputFormat, dst: &Path) -> Result<(), Box<dyn Erro
     for (code, desc) in long_codes {
         err_map.insert(code.to_string(), ErrorMetadata {
             description: desc.map(String::from),
-            // FIXME: this indicates that the error code is not used, which may not be true.
-            // We currently do not use this information.
-            use_site: None,
         });
     }
     match format {