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>

Author: davidtwco

Cargo.lock

@@ -3645,13 +3645,23 @@ dependencies = [
 name = "rustc_error_codes"
 version = "0.0.0"
 
+[[package]]
+name = "rustc_error_messages"
+version = "0.0.0"
+dependencies = [
+ "rustc_macros",
+ "rustc_serialize",
+ "rustc_span",
+]
+
 [[package]]
 name = "rustc_errors"
 version = "0.0.0"
 dependencies = [
  "annotate-snippets",
  "atty",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_lint_defs",
  "rustc_macros",
  "rustc_serialize",
@@ -3708,6 +3718,7 @@ dependencies = [
  "odht",
  "rustc_ast",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_feature",
  "rustc_index",
  "rustc_macros",
@@ -3864,6 +3875,7 @@ version = "0.0.0"
 dependencies = [
  "rustc_ast",
  "rustc_data_structures",
+ "rustc_error_messages",
  "rustc_hir",
  "rustc_macros",
  "rustc_serialize",

compiler/rustc_borrowck/src/borrowck_errors.rs

@@ -1,6 +1,6 @@
-use rustc_errors::{struct_span_err, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
+use rustc_errors::{struct_span_err, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed, MultiSpan};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::{MultiSpan, Span};
+use rustc_span::Span;
 
 impl<'cx, 'tcx> crate::MirBorrowckCtxt<'cx, 'tcx> {
     crate fn cannot_move_when_borrowed(

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1,7 +1,7 @@
 use either::Either;
 use rustc_const_eval::util::CallKind;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind};
@@ -15,7 +15,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::{self, subst::Subst, suggest_constraining_type_params, PredicateKind, Ty};
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::symbol::sym;
-use rustc_span::{BytePos, MultiSpan, Span};
+use rustc_span::{BytePos, Span};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::TraitEngineExt as _;
 

compiler/rustc_builtin_macros/src/format.rs

@@ -7,11 +7,11 @@ use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{token, BlockCheckMode, UnsafeSource};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_errors::{pluralize, Applicability, PResult};
+use rustc_errors::{pluralize, Applicability, MultiSpan, PResult};
 use rustc_expand::base::{self, *};
 use rustc_parse_format as parse;
 use rustc_span::symbol::{sym, Ident, Symbol};
-use rustc_span::{InnerSpan, MultiSpan, Span};
+use rustc_span::{InnerSpan, Span};
 use smallvec::SmallVec;
 
 use std::borrow::Cow;
@@ -446,7 +446,9 @@ impl<'a, 'b> Context<'a, 'b> {
                                 .iter()
                                 .filter(|fmt| fmt.precision_span.is_some())
                                 .count();
-                        e.span_label(span, &format!(
+                        e.span_label(
+                            span,
+                            &format!(
                             "this precision flag adds an extra required argument at position {}, \
                              which is why there {} expected",
                             pos,
@@ -455,7 +457,8 @@ impl<'a, 'b> Context<'a, 'b> {
                             } else {
                                 format!("are {} arguments", count)
                             },
-                        ));
+                        ),
+                        );
                         if let Some(arg) = self.args.get(pos) {
                             e.span_label(
                                 arg.span,

compiler/rustc_error_messages/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "rustc_error_messages"
+version = "0.0.0"
+edition = "2021"
+
+[lib]
+doctest = false
+
+[dependencies]
+rustc_serialize = { path = "../rustc_serialize" }
+rustc_span = { path = "../rustc_span" }
+rustc_macros = { path = "../rustc_macros" }

compiler/rustc_error_messages/src/lib.rs

@@ -0,0 +1,171 @@
+use rustc_macros::{Decodable, Encodable};
+use rustc_span::Span;
+
+/// Abstraction over a message in a diagnostic to support both translatable and non-translatable
+/// diagnostic messages.
+#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
+pub enum DiagnosticMessage {
+    /// Non-translatable diagnostic message.
+    Str(String),
+    /// Identifier for a Fluent message corresponding to the diagnostic message.
+    FluentIdentifier(String),
+}
+
+impl DiagnosticMessage {
+    /// Convert `DiagnosticMessage` to a `&str`.
+    pub fn as_str(&self) -> &str {
+        match self {
+            DiagnosticMessage::Str(msg) => msg,
+            DiagnosticMessage::FluentIdentifier(..) => unimplemented!(),
+        }
+    }
+
+    /// Convert `DiagnosticMessage` to an owned `String`.
+    pub fn to_string(self) -> String {
+        match self {
+            DiagnosticMessage::Str(msg) => msg,
+            DiagnosticMessage::FluentIdentifier(..) => unimplemented!(),
+        }
+    }
+}
+
+/// A span together with some additional data.
+#[derive(Clone, Debug)]
+pub struct SpanLabel {
+    /// The span we are going to include in the final snippet.
+    pub span: Span,
+
+    /// Is this a primary span? This is the "locus" of the message,
+    /// and is indicated with a `^^^^` underline, versus `----`.
+    pub is_primary: bool,
+
+    /// What label should we attach to this span (if any)?
+    pub label: Option<DiagnosticMessage>,
+}
+
+/// A collection of `Span`s.
+///
+/// Spans have two orthogonal attributes:
+///
+/// - They can be *primary spans*. In this case they are the locus of
+///   the error, and would be rendered with `^^^`.
+/// - They can have a *label*. In this case, the label is written next
+///   to the mark in the snippet when we render.
+#[derive(Clone, Debug, Hash, PartialEq, Eq, Encodable, Decodable)]
+pub struct MultiSpan {
+    primary_spans: Vec<Span>,
+    span_labels: Vec<(Span, DiagnosticMessage)>,
+}
+
+impl MultiSpan {
+    #[inline]
+    pub fn new() -> MultiSpan {
+        MultiSpan { primary_spans: vec![], span_labels: vec![] }
+    }
+
+    pub fn from_span(primary_span: Span) -> MultiSpan {
+        MultiSpan { primary_spans: vec![primary_span], span_labels: vec![] }
+    }
+
+    pub fn from_spans(mut vec: Vec<Span>) -> MultiSpan {
+        vec.sort();
+        MultiSpan { primary_spans: vec, span_labels: vec![] }
+    }
+
+    pub fn push_span_label(&mut self, span: Span, label: String) {
+        self.span_labels.push((span, DiagnosticMessage::Str(label)));
+    }
+
+    pub fn push_span_message(&mut self, span: Span, message: DiagnosticMessage) {
+        self.span_labels.push((span, message));
+    }
+
+    /// Selects the first primary span (if any).
+    pub fn primary_span(&self) -> Option<Span> {
+        self.primary_spans.first().cloned()
+    }
+
+    /// Returns all primary spans.
+    pub fn primary_spans(&self) -> &[Span] {
+        &self.primary_spans
+    }
+
+    /// Returns `true` if any of the primary spans are displayable.
+    pub fn has_primary_spans(&self) -> bool {
+        self.primary_spans.iter().any(|sp| !sp.is_dummy())
+    }
+
+    /// Returns `true` if this contains only a dummy primary span with any hygienic context.
+    pub fn is_dummy(&self) -> bool {
+        let mut is_dummy = true;
+        for span in &self.primary_spans {
+            if !span.is_dummy() {
+                is_dummy = false;
+            }
+        }
+        is_dummy
+    }
+
+    /// Replaces all occurrences of one Span with another. Used to move `Span`s in areas that don't
+    /// display well (like std macros). Returns whether replacements occurred.
+    pub fn replace(&mut self, before: Span, after: Span) -> bool {
+        let mut replacements_occurred = false;
+        for primary_span in &mut self.primary_spans {
+            if *primary_span == before {
+                *primary_span = after;
+                replacements_occurred = true;
+            }
+        }
+        for span_label in &mut self.span_labels {
+            if span_label.0 == before {
+                span_label.0 = after;
+                replacements_occurred = true;
+            }
+        }
+        replacements_occurred
+    }
+
+    /// Returns the strings to highlight. We always ensure that there
+    /// is an entry for each of the primary spans -- for each primary
+    /// span `P`, if there is at least one label with span `P`, we return
+    /// those labels (marked as primary). But otherwise we return
+    /// `SpanLabel` instances with empty labels.
+    pub fn span_labels(&self) -> Vec<SpanLabel> {
+        let is_primary = |span| self.primary_spans.contains(&span);
+
+        let mut span_labels = self
+            .span_labels
+            .iter()
+            .map(|&(span, ref label)| SpanLabel {
+                span,
+                is_primary: is_primary(span),
+                label: Some(label.clone()),
+            })
+            .collect::<Vec<_>>();
+
+        for &span in &self.primary_spans {
+            if !span_labels.iter().any(|sl| sl.span == span) {
+                span_labels.push(SpanLabel { span, is_primary: true, label: None });
+            }
+        }
+
+        span_labels
+    }
+
+    /// Returns `true` if any of the span labels is displayable.
+    pub fn has_span_labels(&self) -> bool {
+        self.span_labels.iter().any(|(sp, _)| !sp.is_dummy())
+    }
+}
+
+impl From<Span> for MultiSpan {
+    fn from(span: Span) -> MultiSpan {
+        MultiSpan::from_span(span)
+    }
+}
+
+impl From<Vec<Span>> for MultiSpan {
+    fn from(spans: Vec<Span>) -> MultiSpan {
+        MultiSpan::from_spans(spans)
+    }
+}

compiler/rustc_errors/Cargo.toml

@@ -8,6 +8,7 @@ doctest = false
 
 [dependencies]
 tracing = "0.1"
+rustc_error_messages = { path = "../rustc_error_messages" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_macros = { path = "../rustc_macros" }

compiler/rustc_errors/src/annotate_snippet_emitter_writer.rs

@@ -7,12 +7,12 @@
 
 use crate::emitter::FileWithAnnotatedLines;
 use crate::snippet::Line;
-use crate::{CodeSuggestion, Diagnostic, DiagnosticId, Emitter, Level, SubDiagnostic};
+use crate::{CodeSuggestion, Diagnostic, DiagnosticId, Emitter, Level, MultiSpan, SubDiagnostic};
 use annotate_snippets::display_list::{DisplayList, FormatOptions};
 use annotate_snippets::snippet::*;
 use rustc_data_structures::sync::Lrc;
 use rustc_span::source_map::SourceMap;
-use rustc_span::{MultiSpan, SourceFile};
+use rustc_span::SourceFile;
 
 /// Generates diagnostics using annotate-snippet
 pub struct AnnotateSnippetEmitterWriter {

compiler/rustc_errors/src/diagnostic.rs

@@ -1,15 +1,13 @@
 use crate::snippet::Style;
-use crate::CodeSuggestion;
-use crate::Level;
-use crate::Substitution;
-use crate::SubstitutionPart;
-use crate::SuggestionStyle;
-use crate::ToolMetadata;
+use crate::{
+    CodeSuggestion, DiagnosticMessage, Level, MultiSpan, Substitution, SubstitutionPart,
+    SuggestionStyle, ToolMetadata,
+};
 use rustc_data_structures::stable_map::FxHashMap;
 use rustc_lint_defs::{Applicability, LintExpectationId};
 use rustc_serialize::json::Json;
 use rustc_span::edition::LATEST_STABLE_EDITION;
-use rustc_span::{MultiSpan, Span, DUMMY_SP};
+use rustc_span::{Span, DUMMY_SP};
 use std::fmt;
 use std::hash::{Hash, Hasher};
 
@@ -18,34 +16,6 @@ use std::hash::{Hash, Hasher};
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 pub struct SuggestionsDisabled;
 
-/// Abstraction over a message in a diagnostic to support both translatable and non-translatable
-/// diagnostic messages.
-#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
-pub enum DiagnosticMessage {
-    /// Non-translatable diagnostic message.
-    Str(String),
-    /// Identifier for a Fluent message corresponding to the diagnostic message.
-    FluentIdentifier(String),
-}
-
-impl DiagnosticMessage {
-    /// Convert `DiagnosticMessage` to a `&str`.
-    pub fn as_str(&self) -> &str {
-        match self {
-            DiagnosticMessage::Str(msg) => msg,
-            DiagnosticMessage::FluentIdentifier(..) => unimplemented!(),
-        }
-    }
-
-    /// Convert `DiagnosticMessage` to an owned `String`.
-    pub fn to_string(self) -> String {
-        match self {
-            DiagnosticMessage::Str(msg) => msg,
-            DiagnosticMessage::FluentIdentifier(..) => unimplemented!(),
-        }
-    }
-}
-
 #[must_use]
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub struct Diagnostic {
@@ -262,7 +232,7 @@ impl Diagnostic {
         self.set_span(after);
         for span_label in before.span_labels() {
             if let Some(label) = span_label.label {
-                self.span_label(after, label);
+                self.span.push_span_message(after, label);
             }
         }
         self

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -1,8 +1,8 @@
 use crate::{Diagnostic, DiagnosticId, DiagnosticStyledString, ErrorGuaranteed};
-use crate::{Handler, Level, StashKey};
+use crate::{Handler, Level, MultiSpan, StashKey};
 use rustc_lint_defs::Applicability;
 
-use rustc_span::{MultiSpan, Span};
+use rustc_span::Span;
 use std::fmt::{self, Debug};
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};