Use smaller spans for some structured suggestions

Use more accurate suggestion spans for

* argument parse error
* fully qualified path
* missing code block type
* numeric casts
* E0212

Author: estebank

Diff for: compiler/rustc_errors/src/diagnostic.rs

@@ -298,6 +298,21 @@ impl Diagnostic {
         )
     }
 
+    /// Show a suggestion that has multiple parts to it, always as it's own subdiagnostic.
+    /// In other words, multiple changes need to be applied as part of this suggestion.
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.multipart_suggestion_with_style(
+            msg,
+            suggestion,
+            applicability,
+            SuggestionStyle::ShowAlways,
+        )
+    }
     /// [`Diagnostic::multipart_suggestion()`] but you can set the [`SuggestionStyle`].
     pub fn multipart_suggestion_with_style(
         &mut self,

Diff for: compiler/rustc_errors/src/diagnostic_builder.rs

@@ -257,6 +257,20 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::multipart_suggestion()`].
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.0.allow_suggestions {
+            return self;
+        }
+        self.0.diagnostic.multipart_suggestion_verbose(msg, suggestion, applicability);
+        self
+    }
+
     /// See [`Diagnostic::tool_only_multipart_suggestion()`].
     pub fn tool_only_multipart_suggestion(
         &mut self,

Diff for: compiler/rustc_parse/src/parser/diagnostics.rs

@@ -1618,50 +1618,57 @@ impl<'a> Parser<'a> {
         {
             let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
 
-            let (ident, self_sugg, param_sugg, type_sugg) = match pat.kind {
-                PatKind::Ident(_, ident, _) => (
-                    ident,
-                    format!("self: {}", ident),
-                    format!("{}: TypeName", ident),
-                    format!("_: {}", ident),
-                ),
-                // Also catches `fn foo(&a)`.
-                PatKind::Ref(ref pat, mutab)
-                    if matches!(pat.clone().into_inner().kind, PatKind::Ident(..)) =>
-                {
-                    match pat.clone().into_inner().kind {
-                        PatKind::Ident(_, ident, _) => {
-                            let mutab = mutab.prefix_str();
-                            (
-                                ident,
-                                format!("self: &{}{}", mutab, ident),
-                                format!("{}: &{}TypeName", ident, mutab),
-                                format!("_: &{}{}", mutab, ident),
-                            )
+            let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
+                match pat.kind {
+                    PatKind::Ident(_, ident, _) => (
+                        ident,
+                        "self: ".to_string(),
+                        ": TypeName".to_string(),
+                        "_: ".to_string(),
+                        pat.span.shrink_to_lo(),
+                        pat.span.shrink_to_hi(),
+                        pat.span.shrink_to_lo(),
+                    ),
+                    // Also catches `fn foo(&a)`.
+                    PatKind::Ref(ref inner_pat, mutab)
+                        if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
+                    {
+                        match inner_pat.clone().into_inner().kind {
+                            PatKind::Ident(_, ident, _) => {
+                                let mutab = mutab.prefix_str();
+                                (
+                                    ident,
+                                    "self: ".to_string(),
+                                    format!("{}: &{}TypeName", ident, mutab),
+                                    "_: ".to_string(),
+                                    pat.span.shrink_to_lo(),
+                                    pat.span,
+                                    pat.span.shrink_to_lo(),
+                                )
+                            }
+                            _ => unreachable!(),
                         }
-                        _ => unreachable!(),
-                    }
-                }
-                _ => {
-                    // Otherwise, try to get a type and emit a suggestion.
-                    if let Some(ty) = pat.to_ty() {
-                        err.span_suggestion_verbose(
-                            pat.span,
-                            "explicitly ignore the parameter name",
-                            format!("_: {}", pprust::ty_to_string(&ty)),
-                            Applicability::MachineApplicable,
-                        );
-                        err.note(rfc_note);
                     }
+                    _ => {
+                        // Otherwise, try to get a type and emit a suggestion.
+                        if let Some(ty) = pat.to_ty() {
+                            err.span_suggestion_verbose(
+                                pat.span,
+                                "explicitly ignore the parameter name",
+                                format!("_: {}", pprust::ty_to_string(&ty)),
+                                Applicability::MachineApplicable,
+                            );
+                            err.note(rfc_note);
+                        }
 
-                    return None;
-                }
-            };
+                        return None;
+                    }
+                };
 
             // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
             if first_param {
                 err.span_suggestion(
-                    pat.span,
+                    self_span,
                     "if this is a `self` type, give it a parameter name",
                     self_sugg,
                     Applicability::MaybeIncorrect,
@@ -1671,14 +1678,14 @@ impl<'a> Parser<'a> {
             // `fn foo(HashMap: TypeName<u32>)`.
             if self.token != token::Lt {
                 err.span_suggestion(
-                    pat.span,
+                    param_span,
                     "if this is a parameter name, give it a type",
                     param_sugg,
                     Applicability::HasPlaceholders,
                 );
             }
             err.span_suggestion(
-                pat.span,
+                type_span,
                 "if this is a type, explicitly ignore the parameter name",
                 type_sugg,
                 Applicability::MachineApplicable,

Diff for: compiler/rustc_resolve/src/late/diagnostics.rs

@@ -12,7 +12,7 @@ use rustc_ast::{
 };
 use rustc_ast_pretty::pprust::path_segment_to_string;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, SuggestionStyle};
+use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
@@ -1950,11 +1950,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                             introduce_suggestion.push((*span, formatter(&lt_name)));
                         }
                     }
-                    err.multipart_suggestion_with_style(
+                    err.multipart_suggestion_verbose(
                         &msg,
                         introduce_suggestion,
                         Applicability::MaybeIncorrect,
-                        SuggestionStyle::ShowAlways,
                     );
                 }
 
@@ -1966,14 +1965,13 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                     })
                     .map(|(formatter, span)| (*span, formatter(name)))
                     .collect();
-                err.multipart_suggestion_with_style(
+                err.multipart_suggestion_verbose(
                     &format!(
                         "consider using the `{}` lifetime",
                         lifetime_names.iter().next().unwrap()
                     ),
                     spans_suggs,
                     Applicability::MaybeIncorrect,
-                    SuggestionStyle::ShowAlways,
                 );
             };
         let suggest_new = |err: &mut DiagnosticBuilder<'_>, suggs: Vec<Option<String>>| {
@@ -2064,11 +2062,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                             };
                             spans_suggs.push((span, sugg.to_string()));
                         }
-                        err.multipart_suggestion_with_style(
+                        err.multipart_suggestion_verbose(
                             "consider using the `'static` lifetime",
                             spans_suggs,
                             Applicability::MaybeIncorrect,
-                            SuggestionStyle::ShowAlways,
                         );
                         continue;
                     }
@@ -2088,11 +2085,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                         introduce_suggestion.push((span, sugg.to_string()));
                     }
                 }
-                err.multipart_suggestion_with_style(
+                err.multipart_suggestion_verbose(
                     &msg,
                     introduce_suggestion,
                     Applicability::MaybeIncorrect,
-                    SuggestionStyle::ShowAlways,
                 );
                 if should_break {
                     break;
@@ -2167,11 +2163,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                 if spans_suggs.len() > 0 {
                     // This happens when we have `Foo<T>` where we point at the space before `T`,
                     // but this can be confusing so we give a suggestion with placeholders.
-                    err.multipart_suggestion_with_style(
+                    err.multipart_suggestion_verbose(
                         "consider using one of the available lifetimes here",
                         spans_suggs,
                         Applicability::HasPlaceholders,
-                        SuggestionStyle::ShowAlways,
                     );
                 }
             }

Diff for: compiler/rustc_typeck/src/astconv/mod.rs

@@ -1648,14 +1648,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             constraint=constraint,
                         ));
                     } else {
-                        err.span_suggestion(
-                            span,
+                        err.span_suggestion_verbose(
+                            span.with_hi(assoc_name.span.lo()),
                             "use fully qualified syntax to disambiguate",
                             format!(
-                                "<{} as {}>::{}",
+                                "<{} as {}>::",
                                 ty_param_name(),
                                 bound.print_only_trait_path(),
-                                assoc_name,
                             ),
                             Applicability::MaybeIncorrect,
                         );