Rollup merge of rust-lang#119566 - Zalathar:remove-spanview, r=Swatin…

…em,Nilstrieb

Remove `-Zdump-mir-spanview`

The `-Zdump-mir-spanview` flag was added back in rust-lang#76074, as a development/debugging aid for the initial work on what would eventually become `-Cinstrument-coverage`. It causes the compiler to emit an HTML file containing a function's source code, with various spans highlighted based on the contents of MIR.

When the suggestion was made to [triage and remove unnecessary `-Z` flags (Zulip)](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/.60-Z.60.20option.20triage), I noted that this flag could potentially be worth removing, but I wanted to keep it around to see whether I found it useful for my own coverage work.

But when I actually tried to use it, I ran into various issues (e.g. it crashes on `tests/coverage/closure.rs`). If I can't trust it to work properly without a full overhaul, then instead of diving down a rabbit hole of trying to fix arcane span-handling bugs, it seems better to just remove this obscure old code entirely.

---

````@rustbot```` label +A-code-coverage

compiler/rustc_interface/src/tests.rs

@@ -6,8 +6,8 @@ use rustc_session::config::{
     build_configuration, build_session_options, rustc_optgroups, BranchProtection, CFGuard, Cfg,
     DebugInfo, DumpMonoStatsFormat, ErrorOutputType, ExternEntry, ExternLocation, Externs,
     FunctionReturn, InliningThreshold, Input, InstrumentCoverage, InstrumentXRay,
-    LinkSelfContained, LinkerPluginLto, LocationDetail, LtoCli, MirSpanview, NextSolverConfig,
-    OomStrategy, Options, OutFileName, OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius,
+    LinkSelfContained, LinkerPluginLto, LocationDetail, LtoCli, NextSolverConfig, OomStrategy,
+    Options, OutFileName, OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius,
     ProcMacroExecutionStrategy, Strip, SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
 };
 use rustc_session::lint::Level;
@@ -666,7 +666,6 @@ fn test_unstable_options_tracking_hash() {
     untracked!(dump_mir_dir, String::from("abc"));
     untracked!(dump_mir_exclude_pass_number, true);
     untracked!(dump_mir_graphviz, true);
-    untracked!(dump_mir_spanview, Some(MirSpanview::Statement));
     untracked!(dump_mono_stats, SwitchWithOptPath::Enabled(Some("mono-items-dir/".into())));
     untracked!(dump_mono_stats_format, DumpMonoStatsFormat::Json);
     untracked!(dylib_lto, true);

compiler/rustc_middle/src/mir/mod.rs

@@ -55,7 +55,6 @@ pub mod mono;
 pub mod patch;
 pub mod pretty;
 mod query;
-pub mod spanview;
 mod statement;
 mod syntax;
 pub mod tcx;

compiler/rustc_middle/src/mir/pretty.rs

@@ -5,7 +5,6 @@ use std::io::{self, Write as _};
 use std::path::{Path, PathBuf};
 
 use super::graphviz::write_mir_fn_graphviz;
-use super::spanview::write_mir_fn_spanview;
 use rustc_ast::InlineAsmTemplatePiece;
 use rustc_middle::mir::interpret::{
     alloc_range, read_target_uint, AllocBytes, AllocId, Allocation, GlobalAlloc, Pointer,
@@ -141,16 +140,6 @@ fn dump_matched_mir_node<'tcx, F>(
             write_mir_fn_graphviz(tcx, body, false, &mut file)?;
         };
     }
-
-    if let Some(spanview) = tcx.sess.opts.unstable_opts.dump_mir_spanview {
-        let _: io::Result<()> = try {
-            let file_basename = dump_file_basename(tcx, pass_num, pass_name, disambiguator, body);
-            let mut file = create_dump_file_with_basename(tcx, &file_basename, "html")?;
-            if body.source.def_id().is_local() {
-                write_mir_fn_spanview(tcx, body, spanview, &file_basename, &mut file)?;
-            }
-        };
-    }
 }
 
 /// Returns the file basename portion (without extension) of a filename path