Merge branch 'master' into rusty-hermit

5 files changed, 166 insertions, 78 deletions

diff --git a/src/librustc_errors/annotate_snippet_emitter_writer.rs b/src/librustc_errors/annotate_snippet_emitter_writer.rs
index 0281d10fd93..491bc2aa6a2 100644
--- a/src/librustc_errors/annotate_snippet_emitter_writer.rs
+++ b/src/librustc_errors/annotate_snippet_emitter_writer.rs
@@ -31,24 +31,28 @@ pub struct AnnotateSnippetEmitterWriter {
 
 impl Emitter for AnnotateSnippetEmitterWriter {
     /// The entry point for the diagnostics generation
-    fn emit_diagnostic(&mut self, db: &Diagnostic) {
-        let mut children = db.children.clone();
-        let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        let mut children = diag.children.clone();
+        let (mut primary_span, suggestions) = self.primary_span_formatted(&diag);
 
         self.fix_multispans_in_std_macros(&self.source_map,
                                           &mut primary_span,
                                           &mut children,
-                                          &db.level,
+                                          &diag.level,
                                           self.external_macro_backtrace);
 
-        self.emit_messages_default(&db.level,
-                                   db.message(),
-                                   &db.code,
+        self.emit_messages_default(&diag.level,
+                                   diag.message(),
+                                   &diag.code,
                                    &primary_span,
                                    &children,
                                    &suggestions);
     }
 
+    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> {
+        self.source_map.as_ref()
+    }
+
     fn should_show_explain(&self) -> bool {
         !self.short_message
     }
diff --git a/src/librustc_errors/diagnostic.rs b/src/librustc_errors/diagnostic.rs
index 3f1b91256c4..fd74d8673da 100644
--- a/src/librustc_errors/diagnostic.rs
+++ b/src/librustc_errors/diagnostic.rs
@@ -298,9 +298,31 @@ impl Diagnostic {
     /// * may contain a name of a function, variable, or type, but not whole expressions
     ///
     /// See `CodeSuggestion` for more information.
-    pub fn span_suggestion(&mut self, sp: Span, msg: &str,
-                                       suggestion: String,
-                                       applicability: Applicability) -> &mut Self {
+    pub fn span_suggestion(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.span_suggestion_with_style(
+            sp,
+            msg,
+            suggestion,
+            applicability,
+            SuggestionStyle::ShowCode,
+        );
+        self
+    }
+
+    pub fn span_suggestion_with_style(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+        style: SuggestionStyle,
+    ) -> &mut Self {
         self.suggestions.push(CodeSuggestion {
             substitutions: vec![Substitution {
                 parts: vec![SubstitutionPart {
@@ -309,16 +331,37 @@ impl Diagnostic {
                 }],
             }],
             msg: msg.to_owned(),
-            style: SuggestionStyle::ShowCode,
+            style,
             applicability,
         });
         self
     }
 
+    pub fn span_suggestion_verbose(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.span_suggestion_with_style(
+            sp,
+            msg,
+            suggestion,
+            applicability,
+            SuggestionStyle::ShowAlways,
+        );
+        self
+    }
+
     /// Prints out a message with multiple suggested edits of the code.
-    pub fn span_suggestions(&mut self, sp: Span, msg: &str,
-        suggestions: impl Iterator<Item = String>, applicability: Applicability) -> &mut Self
-    {
+    pub fn span_suggestions(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestions: impl Iterator<Item = String>,
+        applicability: Applicability,
+    ) -> &mut Self {
         self.suggestions.push(CodeSuggestion {
             substitutions: suggestions.map(|snippet| Substitution {
                 parts: vec![SubstitutionPart {
@@ -340,17 +383,13 @@ impl Diagnostic {
     pub fn span_suggestion_short(
         &mut self, sp: Span, msg: &str, suggestion: String, applicability: Applicability
     ) -> &mut Self {
-        self.suggestions.push(CodeSuggestion {
-            substitutions: vec![Substitution {
-                parts: vec![SubstitutionPart {
-                    snippet: suggestion,
-                    span: sp,
-                }],
-            }],
-            msg: msg.to_owned(),
-            style: SuggestionStyle::HideCodeInline,
+        self.span_suggestion_with_style(
+            sp,
+            msg,
+            suggestion,
             applicability,
-        });
+            SuggestionStyle::HideCodeInline,
+        );
         self
     }
 
@@ -363,17 +402,13 @@ impl Diagnostic {
     pub fn span_suggestion_hidden(
         &mut self, sp: Span, msg: &str, suggestion: String, applicability: Applicability
     ) -> &mut Self {
-        self.suggestions.push(CodeSuggestion {
-            substitutions: vec![Substitution {
-                parts: vec![SubstitutionPart {
-                    snippet: suggestion,
-                    span: sp,
-                }],
-            }],
-            msg: msg.to_owned(),
-            style: SuggestionStyle::HideCodeAlways,
+        self.span_suggestion_with_style(
+            sp,
+            msg,
+            suggestion,
             applicability,
-        });
+            SuggestionStyle::HideCodeAlways,
+        );
         self
     }
 
@@ -384,17 +419,13 @@ impl Diagnostic {
     pub fn tool_only_span_suggestion(
         &mut self, sp: Span, msg: &str, suggestion: String, applicability: Applicability
     ) -> &mut Self {
-        self.suggestions.push(CodeSuggestion {
-            substitutions: vec![Substitution {
-                parts: vec![SubstitutionPart {
-                    snippet: suggestion,
-                    span: sp,
-                }],
-            }],
-            msg: msg.to_owned(),
-            style: SuggestionStyle::CompletelyHidden,
+        self.span_suggestion_with_style(
+            sp,
+            msg,
+            suggestion,
             applicability,
-        });
+            SuggestionStyle::CompletelyHidden,
+        );
         self
     }
 
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 9aea46da68b..1e486786f68 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -13,7 +13,7 @@ use syntax_pos::{SourceFile, Span, MultiSpan};
 
 use crate::{
     Level, CodeSuggestion, Diagnostic, SubDiagnostic,
-    SuggestionStyle, SourceMapperDyn, DiagnosticId,
+    SuggestionStyle, SourceMapper, SourceMapperDyn, DiagnosticId,
 };
 use crate::Level::Error;
 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
@@ -180,7 +180,7 @@ const ANONYMIZED_LINE_NUM: &str = "LL";
 /// Emitter trait for emitting errors.
 pub trait Emitter {
     /// Emit a structured diagnostic.
-    fn emit_diagnostic(&mut self, db: &Diagnostic);
+    fn emit_diagnostic(&mut self, diag: &Diagnostic);
 
     /// Emit a notification that an artifact has been output.
     /// This is currently only supported for the JSON format,
@@ -192,6 +192,8 @@ pub trait Emitter {
         true
     }
 
+    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>>;
+
     /// Formats the substitutions of the primary_span
     ///
     /// The are a lot of conditions to this method, but in short:
@@ -204,10 +206,10 @@ pub trait Emitter {
     ///   we return the original `primary_span` and the original suggestions.
     fn primary_span_formatted<'a>(
         &mut self,
-        db: &'a Diagnostic
+        diag: &'a Diagnostic,
     ) -> (MultiSpan, &'a [CodeSuggestion]) {
-        let mut primary_span = db.span.clone();
-        if let Some((sugg, rest)) = db.suggestions.split_first() {
+        let mut primary_span = diag.span.clone();
+        if let Some((sugg, rest)) = diag.suggestions.split_first() {
             if rest.is_empty() &&
                // ^ if there is only one suggestion
                // don't display multi-suggestions as labels
@@ -218,10 +220,14 @@ pub trait Emitter {
                sugg.msg.split_whitespace().count() < 10 &&
                // don't display multiline suggestions as labels
                !sugg.substitutions[0].parts[0].snippet.contains('\n') &&
-               // when this style is set we want the suggestion to be a message, not inline
-               sugg.style != SuggestionStyle::HideCodeAlways &&
-               // trivial suggestion for tooling's sake, never shown
-               sugg.style != SuggestionStyle::CompletelyHidden
+               ![
+                    // when this style is set we want the suggestion to be a message, not inline
+                    SuggestionStyle::HideCodeAlways,
+                    // trivial suggestion for tooling's sake, never shown
+                    SuggestionStyle::CompletelyHidden,
+                    // subtle suggestion, never shown inline
+                    SuggestionStyle::ShowAlways,
+               ].contains(&sugg.style)
             {
                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
@@ -230,7 +236,20 @@ pub trait Emitter {
                     format!("help: {}", sugg.msg)
                 } else {
                     // Show the default suggestion text with the substitution
-                    format!("help: {}: `{}`", sugg.msg, substitution)
+                    format!(
+                        "help: {}{}: `{}`",
+                        sugg.msg,
+                        if self.source_map().map(|sm| is_case_difference(
+                            &**sm,
+                            substitution,
+                            sugg.substitutions[0].parts[0].span,
+                        )).unwrap_or(false) {
+                            " (notice the capitalization)"
+                        } else {
+                            ""
+                        },
+                        substitution,
+                    )
                 };
                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
 
@@ -241,10 +260,10 @@ pub trait Emitter {
                 // to be consistent. We could try to figure out if we can
                 // make one (or the first one) inline, but that would give
                 // undue importance to a semi-random suggestion
-                (primary_span, &db.suggestions)
+                (primary_span, &diag.suggestions)
             }
         } else {
-            (primary_span, &db.suggestions)
+            (primary_span, &diag.suggestions)
         }
     }
 
@@ -378,19 +397,23 @@ pub trait Emitter {
 }
 
 impl Emitter for EmitterWriter {
-    fn emit_diagnostic(&mut self, db: &Diagnostic) {
-        let mut children = db.children.clone();
-        let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
+    fn source_map(&self) -> Option<&Lrc<SourceMapperDyn>> {
+        self.sm.as_ref()
+    }
+
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        let mut children = diag.children.clone();
+        let (mut primary_span, suggestions) = self.primary_span_formatted(&diag);
 
         self.fix_multispans_in_std_macros(&self.sm,
                                           &mut primary_span,
                                           &mut children,
-                                          &db.level,
+                                          &diag.level,
                                           self.external_macro_backtrace);
 
-        self.emit_messages_default(&db.level,
-                                   &db.styled_message(),
-                                   &db.code,
+        self.emit_messages_default(&diag.level,
+                                   &diag.styled_message(),
+                                   &diag.code,
                                    &primary_span,
                                    &children,
                                    &suggestions);
@@ -1457,7 +1480,9 @@ impl EmitterWriter {
         let suggestions = suggestion.splice_lines(&**sm);
 
         let mut row_num = 2;
-        for &(ref complete, ref parts) in suggestions.iter().take(MAX_SUGGESTIONS) {
+        let mut notice_capitalization = false;
+        for (complete, parts, only_capitalization) in suggestions.iter().take(MAX_SUGGESTIONS) {
+            notice_capitalization |= only_capitalization;
             // Only show underline if the suggestion spans a single line and doesn't cover the
             // entirety of the code output. If you have multiple replacements in the same line
             // of code, show the underline.
@@ -1548,7 +1573,10 @@ impl EmitterWriter {
         }
         if suggestions.len() > MAX_SUGGESTIONS {
             let msg = format!("and {} other candidates", suggestions.len() - MAX_SUGGESTIONS);
-            buffer.puts(row_num, 0, &msg, Style::NoStyle);
+            buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
+        } else if notice_capitalization {
+            let msg = "notice the capitalization difference";
+            buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
         }
         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
         Ok(())
@@ -2030,3 +2058,18 @@ impl<'a> Drop for WritableDst<'a> {
         }
     }
 }
+
+/// Whether the original and suggested code are visually similar enough to warrant extra wording.
+pub fn is_case_difference(sm: &dyn SourceMapper, suggested: &str, sp: Span) -> bool {
+    // FIXME: this should probably be extended to also account for `FO0` → `FOO` and unicode.
+    let found = sm.span_to_snippet(sp).unwrap();
+    let ascii_confusables = &['c', 'f', 'i', 'k', 'o', 's', 'u', 'v', 'w', 'x', 'y', 'z'];
+    // All the chars that differ in capitalization are confusable (above):
+    let confusable = found.chars().zip(suggested.chars()).filter(|(f, s)| f != s).all(|(f, s)| {
+        (ascii_confusables.contains(&f) || ascii_confusables.contains(&s))
+    });
+    confusable && found.to_lowercase() == suggested.to_lowercase()
+            // FIXME: We sometimes suggest the same thing we already have, which is a
+            //        bug, but be defensive against that here.
+            && found != suggested
+}
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index f9dc13ce97e..63df052a225 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -13,7 +13,7 @@ pub use emitter::ColorConfig;
 
 use Level::*;
 
-use emitter::{Emitter, EmitterWriter};
+use emitter::{Emitter, EmitterWriter, is_case_difference};
 use registry::Registry;
 
 use rustc_data_structures::sync::{self, Lrc, Lock};
@@ -37,13 +37,16 @@ pub mod registry;
 mod styled_buffer;
 mod lock;
 
-use syntax_pos::{BytePos,
-                 Loc,
-                 FileLinesResult,
-                 SourceFile,
-                 FileName,
-                 MultiSpan,
-                 Span};
+use syntax_pos::{
+    BytePos,
+    FileLinesResult,
+    FileName,
+    Loc,
+    MultiSpan,
+    SourceFile,
+    Span,
+    SpanSnippetError,
+};
 
 /// Indicates the confidence in the correctness of a suggestion.
 ///
@@ -81,6 +84,8 @@ pub enum SuggestionStyle {
     /// This will *not* show the code if the suggestion is inline *and* the suggested code is
     /// empty.
     ShowCode,
+    /// Always show the suggested code independently.
+    ShowAlways,
 }
 
 impl SuggestionStyle {
@@ -145,6 +150,7 @@ pub trait SourceMapper {
     fn lookup_char_pos(&self, pos: BytePos) -> Loc;
     fn span_to_lines(&self, sp: Span) -> FileLinesResult;
     fn span_to_string(&self, sp: Span) -> String;
+    fn span_to_snippet(&self, sp: Span) -> Result<String, SpanSnippetError>;
     fn span_to_filename(&self, sp: Span) -> FileName;
     fn merge_spans(&self, sp_lhs: Span, sp_rhs: Span) -> Option<Span>;
     fn call_span_if_macro(&self, sp: Span) -> Span;
@@ -153,9 +159,12 @@ pub trait SourceMapper {
 }
 
 impl CodeSuggestion {
-    /// Returns the assembled code suggestions and whether they should be shown with an underline.
-    pub fn splice_lines(&self, cm: &SourceMapperDyn)
-                        -> Vec<(String, Vec<SubstitutionPart>)> {
+    /// Returns the assembled code suggestions, whether they should be shown with an underline
+    /// and whether the substitution only differs in capitalization.
+    pub fn splice_lines(
+        &self,
+        cm: &SourceMapperDyn,
+    ) -> Vec<(String, Vec<SubstitutionPart>, bool)> {
         use syntax_pos::{CharPos, Pos};
 
         fn push_trailing(buf: &mut String,
@@ -230,6 +239,7 @@ impl CodeSuggestion {
                 prev_hi = cm.lookup_char_pos(part.span.hi());
                 prev_line = fm.get_line(prev_hi.line - 1);
             }
+            let only_capitalization = is_case_difference(cm, &buf, bounding_span);
             // if the replacement already ends with a newline, don't print the next line
             if !buf.ends_with('\n') {
                 push_trailing(&mut buf, prev_line.as_ref(), &prev_hi, None);
@@ -238,7 +248,7 @@ impl CodeSuggestion {
             while buf.ends_with('\n') {
                 buf.pop();
             }
-            (buf, substitution.parts)
+            (buf, substitution.parts, only_capitalization)
         }).collect()
     }
 }
diff --git a/src/librustc_errors/styled_buffer.rs b/src/librustc_errors/styled_buffer.rs
index 6e03618d2b0..b12ab9e4576 100644
--- a/src/librustc_errors/styled_buffer.rs
+++ b/src/librustc_errors/styled_buffer.rs
@@ -111,7 +111,7 @@ impl StyledBuffer {
 
     pub fn prepend(&mut self, line: usize, string: &str, style: Style) {
         self.ensure_lines(line);
-        let string_len = string.len();
+        let string_len = string.chars().count();
 
         // Push the old content over to make room for new content
         for _ in 0..string_len {