span: move MultiSpan

`MultiSpan` contains labels, which are more complicated with the
introduction of diagnostic translation and will use types from
`rustc_errors` - however, `rustc_errors` depends on `rustc_span` so
`rustc_span` cannot use types like `DiagnosticMessage` without
dependency cycles. Introduce a new `rustc_error_messages` crate that can
contain `DiagnosticMessage` and `MultiSpan`.

Signed-off-by: David Wood <david.wood@huawei.com>

clippy_lints/src/collapsible_match.rs

@@ -3,11 +3,12 @@ use clippy_utils::higher::IfLetOrMatch;
 use clippy_utils::visitors::is_local_used;
 use clippy_utils::{is_lang_ctor, is_unit_expr, path_to_local, peel_blocks_with_stmt, peel_ref_operators, SpanlessEq};
 use if_chain::if_chain;
+use rustc_errors::MultiSpan;
 use rustc_hir::LangItem::OptionNone;
 use rustc_hir::{Arm, Expr, Guard, HirId, Pat, PatKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::{MultiSpan, Span};
+use rustc_span::Span;
 
 declare_clippy_lint! {
     /// ### What it does

clippy_lints/src/doc.rs

@@ -11,7 +11,7 @@ use rustc_ast::token::CommentKind;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::emitter::EmitterWriter;
-use rustc_errors::{Applicability, Handler, SuggestionStyle};
+use rustc_errors::{Applicability, Handler, MultiSpan, SuggestionStyle};
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{AnonConst, Expr};
@@ -25,7 +25,7 @@ use rustc_session::parse::ParseSess;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::edition::Edition;
-use rustc_span::source_map::{BytePos, FilePathMapping, MultiSpan, SourceMap, Span};
+use rustc_span::source_map::{BytePos, FilePathMapping, SourceMap, Span};
 use rustc_span::{sym, FileName, Pos};
 use std::io;
 use std::ops::Range;

clippy_lints/src/loops/needless_collect.rs

@@ -6,7 +6,7 @@ use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::{can_move_expr_to_closure, is_trait_method, path_to_local, path_to_local_id, CaptureKind};
 use if_chain::if_chain;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::Applicability;
+use rustc_errors::{Applicability, MultiSpan};
 use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
 use rustc_hir::{Block, Expr, ExprKind, HirId, HirIdSet, Local, Mutability, Node, PatKind, Stmt, StmtKind};
 use rustc_lint::LateContext;
@@ -14,7 +14,7 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, Ty};
 use rustc_span::sym;
-use rustc_span::{MultiSpan, Span};
+use rustc_span::Span;
 
 const NEEDLESS_COLLECT_MSG: &str = "avoid using `collect()` when not needed";
 

clippy_lints/src/ptr.rs

@@ -5,7 +5,7 @@ use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::expr_sig;
 use clippy_utils::{get_expr_use_or_unification_node, is_lint_allowed, path_def_id, path_to_local, paths};
 use if_chain::if_chain;
-use rustc_errors::Applicability;
+use rustc_errors::{Applicability, MultiSpan};
 use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::HirIdMap;
 use rustc_hir::intravisit::{walk_expr, Visitor};
@@ -19,8 +19,8 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Span;
+use rustc_span::sym;
 use rustc_span::symbol::Symbol;
-use rustc_span::{sym, MultiSpan};
 use std::fmt;
 use std::iter;
 

clippy_utils/src/diagnostics.rs

@@ -8,10 +8,10 @@
 //! Thank you!
 //! ~The `INTERNAL_METADATA_COLLECTOR` lint
 
-use rustc_errors::{emitter::MAX_SUGGESTION_HIGHLIGHT_LINES, Applicability, Diagnostic};
+use rustc_errors::{emitter::MAX_SUGGESTION_HIGHLIGHT_LINES, Applicability, Diagnostic, MultiSpan};
 use rustc_hir::HirId;
 use rustc_lint::{LateContext, Lint, LintContext};
-use rustc_span::source_map::{MultiSpan, Span};
+use rustc_span::source_map::Span;
 use std::env;
 
 fn docs_link(diag: &mut Diagnostic, lint: &'static Lint) {
@@ -155,7 +155,13 @@ where
     });
 }
 
-pub fn span_lint_hir(cx: &LateContext<'_>, lint: &'static Lint, hir_id: HirId, sp: Span, msg: &str) {
+pub fn span_lint_hir(
+    cx: &LateContext<'_>,
+    lint: &'static Lint,
+    hir_id: HirId,
+    sp: Span,
+    msg: &str,
+) {
     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, |diag| {
         let mut diag = diag.build(msg);
         docs_link(&mut diag, lint);
@@ -272,9 +278,14 @@ pub fn span_lint_and_sugg_for_edges(
         let sugg_lines_count = sugg.lines().count();
         if sugg_lines_count > MAX_SUGGESTION_HIGHLIGHT_LINES {
             let sm = cx.sess().source_map();
-            if let (Ok(line_upper), Ok(line_bottom)) = (sm.lookup_line(sp.lo()), sm.lookup_line(sp.hi())) {
+            if let (Ok(line_upper), Ok(line_bottom)) =
+                (sm.lookup_line(sp.lo()), sm.lookup_line(sp.hi()))
+            {
                 let split_idx = MAX_SUGGESTION_HIGHLIGHT_LINES / 2;
-                let span_upper = sm.span_until_char(sp.with_hi(line_upper.sf.lines[line_upper.line + split_idx]), '\n');
+                let span_upper = sm.span_until_char(
+                    sp.with_hi(line_upper.sf.lines[line_upper.line + split_idx]),
+                    '\n',
+                );
                 let span_bottom = sp.with_lo(line_bottom.sf.lines[line_bottom.line - split_idx]);
 
                 let sugg_lines_vec = sugg.lines().collect::<Vec<&str>>();