Hidden suggestion support

src/librustc/lint/builtin.rs

@@ -557,7 +557,7 @@ impl BuiltinLintDiagnostics {
             }
             BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
                 if !replaces.is_empty() {
-                    db.multipart_suggestion(
+                    db.tool_only_multipart_suggestion(
                         &message,
                         replaces,
                         Applicability::MachineApplicable,

src/librustc_errors/diagnostic.rs

@@ -1,4 +1,5 @@
 use crate::CodeSuggestion;
+use crate::SuggestionStyle;
 use crate::SubstitutionPart;
 use crate::Substitution;
 use crate::Applicability;
@@ -243,7 +244,33 @@ impl Diagnostic {
                     .collect(),
             }],
             msg: msg.to_owned(),
-            show_code_when_inline: true,
+            style: SuggestionStyle::ShowCode,
+            applicability,
+        });
+        self
+    }
+
+    /// Prints out a message with for a multipart suggestion without showing the suggested code.
+    ///
+    /// This is intended to be used for suggestions that are obvious in what the changes need to
+    /// be from the message, showing the span label inline would be visually unpleasant
+    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
+    /// improve understandability.
+    pub fn tool_only_multipart_suggestion(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.suggestions.push(CodeSuggestion {
+            substitutions: vec![Substitution {
+                parts: suggestion
+                    .into_iter()
+                    .map(|(span, snippet)| SubstitutionPart { snippet, span })
+                    .collect(),
+            }],
+            msg: msg.to_owned(),
+            style: SuggestionStyle::CompletelyHidden,
             applicability,
         });
         self
@@ -277,7 +304,7 @@ impl Diagnostic {
                 }],
             }],
             msg: msg.to_owned(),
-            show_code_when_inline: true,
+            style: SuggestionStyle::ShowCode,
             applicability,
         });
         self
@@ -295,7 +322,7 @@ impl Diagnostic {
                 }],
             }).collect(),
             msg: msg.to_owned(),
-            show_code_when_inline: true,
+            style: SuggestionStyle::ShowCode,
             applicability,
         });
         self
@@ -316,7 +343,51 @@ impl Diagnostic {
                 }],
             }],
             msg: msg.to_owned(),
-            show_code_when_inline: false,
+            style: SuggestionStyle::HideCodeInline,
+            applicability,
+        });
+        self
+    }
+
+    /// Prints out a message with for a suggestion without showing the suggested code.
+    ///
+    /// This is intended to be used for suggestions that are obvious in what the changes need to
+    /// be from the message, showing the span label inline would be visually unpleasant
+    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
+    /// improve understandability.
+    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::HideCodeInline,
+            applicability,
+        });
+        self
+    }
+
+    /// Adds a suggestion to the json output, but otherwise remains silent/undisplayed in the cli.
+    ///
+    /// This is intended to be used for suggestions that are *very* obvious in what the changes
+    /// need to be from the message, but we still want other tools to be able to apply them.
+    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,
             applicability: applicability,
         });
         self

src/librustc_errors/diagnostic_builder.rs

@@ -205,6 +205,24 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    pub fn tool_only_multipart_suggestion(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.allow_suggestions {
+            return self
+        }
+        self.diagnostic.tool_only_multipart_suggestion(
+            msg,
+            suggestion,
+            applicability,
+        );
+        self
+    }
+
+
     pub fn span_suggestion(
         &mut self,
         sp: Span,
@@ -261,6 +279,45 @@ impl<'a> DiagnosticBuilder<'a> {
         );
         self
     }
+
+    pub fn span_suggestion_hidden(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.allow_suggestions {
+            return self
+        }
+        self.diagnostic.span_suggestion_hidden(
+            sp,
+            msg,
+            suggestion,
+            applicability,
+        );
+        self
+    }
+
+    pub fn tool_only_span_suggestion(
+        &mut self,
+        sp: Span,
+        msg: &str,
+        suggestion: String,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.allow_suggestions {
+            return self
+        }
+        self.diagnostic.tool_only_span_suggestion(
+            sp,
+            msg,
+            suggestion,
+            applicability,
+        );
+        self
+    }
+
     forward!(pub fn set_span<S: Into<MultiSpan>>(&mut self, sp: S) -> &mut Self);
     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 

src/librustc_errors/emitter.rs

@@ -2,7 +2,10 @@ use Destination::*;
 
 use syntax_pos::{SourceFile, Span, MultiSpan};
 
-use crate::{Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic, SourceMapperDyn, DiagnosticId};
+use crate::{
+    Level, CodeSuggestion, DiagnosticBuilder, SubDiagnostic,
+    SuggestionStyle, SourceMapperDyn, DiagnosticId,
+};
 use crate::snippet::{Annotation, AnnotationType, Line, MultilineAnnotation, StyledString, Style};
 use crate::styled_buffer::StyledBuffer;
 
@@ -43,9 +46,14 @@ impl Emitter for EmitterWriter {
                // don't display long messages as labels
                sugg.msg.split_whitespace().count() < 10 &&
                // don't display multiline suggestions as labels
-               !sugg.substitutions[0].parts[0].snippet.contains('\n') {
+               !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
+            {
                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
-                let msg = if substitution.len() == 0 || !sugg.show_code_when_inline {
+                let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
                     // This substitution is only removal or we explicitly don't want to show the
                     // code inline, don't show it
                     format!("help: {}", sugg.msg)
@@ -942,14 +950,15 @@ impl EmitterWriter {
         }
     }
 
-    fn emit_message_default(&mut self,
-                            msp: &MultiSpan,
-                            msg: &[(String, Style)],
-                            code: &Option<DiagnosticId>,
-                            level: &Level,
-                            max_line_num_len: usize,
-                            is_secondary: bool)
-                            -> io::Result<()> {
+    fn emit_message_default(
+        &mut self,
+        msp: &MultiSpan,
+        msg: &[(String, Style)],
+        code: &Option<DiagnosticId>,
+        level: &Level,
+        max_line_num_len: usize,
+        is_secondary: bool,
+    ) -> io::Result<()> {
         let mut buffer = StyledBuffer::new();
         let header_style = if is_secondary {
             Style::HeaderMsg
@@ -1184,11 +1193,12 @@ impl EmitterWriter {
 
     }
 
-    fn emit_suggestion_default(&mut self,
-                               suggestion: &CodeSuggestion,
-                               level: &Level,
-                               max_line_num_len: usize)
-                               -> io::Result<()> {
+    fn emit_suggestion_default(
+        &mut self,
+        suggestion: &CodeSuggestion,
+        level: &Level,
+        max_line_num_len: usize,
+    ) -> io::Result<()> {
         if let Some(ref sm) = self.sm {
             let mut buffer = StyledBuffer::new();
 
@@ -1198,11 +1208,13 @@ impl EmitterWriter {
                 buffer.append(0, &level_str, Style::Level(level.clone()));
                 buffer.append(0, ": ", Style::HeaderMsg);
             }
-            self.msg_to_buffer(&mut buffer,
-                               &[(suggestion.msg.to_owned(), Style::NoStyle)],
-                               max_line_num_len,
-                               "suggestion",
-                               Some(Style::HeaderMsg));
+            self.msg_to_buffer(
+                &mut buffer,
+                &[(suggestion.msg.to_owned(), Style::NoStyle)],
+                max_line_num_len,
+                "suggestion",
+                Some(Style::HeaderMsg),
+            );
 
             // Render the replacements for each suggestion
             let suggestions = suggestion.splice_lines(&**sm);
@@ -1340,22 +1352,42 @@ impl EmitterWriter {
                 if !self.short_message {
                     for child in children {
                         let span = child.render_span.as_ref().unwrap_or(&child.span);
-                        match self.emit_message_default(&span,
-                                                        &child.styled_message(),
-                                                        &None,
-                                                        &child.level,
-                                                        max_line_num_len,
-                                                        true) {
+                        match self.emit_message_default(
+                            &span,
+                            &child.styled_message(),
+                            &None,
+                            &child.level,
+                            max_line_num_len,
+                            true,
+                        ) {
                             Err(e) => panic!("failed to emit error: {}", e),
                             _ => ()
                         }
                     }
                     for sugg in suggestions {
-                        match self.emit_suggestion_default(sugg,
-                                                           &Level::Help,
-                                                           max_line_num_len) {
-                            Err(e) => panic!("failed to emit error: {}", e),
-                            _ => ()
+                        if sugg.style == SuggestionStyle::CompletelyHidden {
+                            // do not display this suggestion, it is meant only for tools
+                        } else if sugg.style == SuggestionStyle::HideCodeAlways {
+                            match self.emit_message_default(
+                                &MultiSpan::new(),
+                                &[(sugg.msg.to_owned(), Style::HeaderMsg)],
+                                &None,
+                                &Level::Help,
+                                max_line_num_len,
+                                true,
+                            ) {
+                                Err(e) => panic!("failed to emit error: {}", e),
+                                _ => ()
+                            }
+                        } else {
+                            match self.emit_suggestion_default(
+                                sugg,
+                                &Level::Help,
+                                max_line_num_len,
+                            ) {
+                                Err(e) => panic!("failed to emit error: {}", e),
+                                _ => ()
+                            }
                         }
                     }
                 }

src/librustc_errors/lib.rs

@@ -68,6 +68,29 @@ pub enum Applicability {
     Unspecified,
 }
 
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, RustcEncodable, RustcDecodable)]
+pub enum SuggestionStyle {
+    /// Hide the suggested code when displaying this suggestion inline.
+    HideCodeInline,
+    /// Always hide the suggested code but display the message.
+    HideCodeAlways,
+    /// Do not display this suggestion in the cli output, it is only meant for tools.
+    CompletelyHidden,
+    /// Always show the suggested code.
+    /// This will *not* show the code if the suggestion is inline *and* the suggested code is
+    /// empty.
+    ShowCode,
+}
+
+impl SuggestionStyle {
+    fn hide_inline(&self) -> bool {
+        match *self {
+            SuggestionStyle::ShowCode => false,
+            _ => true,
+        }
+    }
+}
+
 #[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub struct CodeSuggestion {
     /// Each substitute can have multiple variants due to multiple
@@ -93,7 +116,8 @@ pub struct CodeSuggestion {
     /// ```
     pub substitutions: Vec<Substitution>,
     pub msg: String,
-    pub show_code_when_inline: bool,
+    /// Visual representation of this suggestion.
+    pub style: SuggestionStyle,
     /// Whether or not the suggestion is approximate
     ///
     /// Sometimes we may show suggestions with placeholders,

src/test/ui/bad/bad-lint-cap2.stderr

@@ -2,7 +2,7 @@ error: unused import: `std::option`
   --> $DIR/bad-lint-cap2.rs:6:5
    |
 LL | use std::option; //~ ERROR
-   | ----^^^^^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/bad-lint-cap2.rs:4:9

src/test/ui/bad/bad-lint-cap3.stderr

@@ -2,7 +2,7 @@ warning: unused import: `std::option`
   --> $DIR/bad-lint-cap3.rs:7:5
    |
 LL | use std::option; //~ WARN
-   | ----^^^^^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/bad-lint-cap3.rs:4:9

src/test/ui/imports/unused.stderr

@@ -2,7 +2,7 @@ error: unused import: `super::f`
   --> $DIR/unused.rs:7:24
    |
 LL |         pub(super) use super::f; //~ ERROR unused
-   |         ---------------^^^^^^^^- help: remove the whole `use` item
+   |                        ^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/unused.rs:1:9

src/test/ui/issues/issue-30730.stderr

@@ -2,7 +2,7 @@ error: unused import: `std::thread`
   --> $DIR/issue-30730.rs:3:5
    |
 LL | use std::thread;
-   | ----^^^^^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/issue-30730.rs:2:9

src/test/ui/lint/lint-directives-on-use-items-issue-10534.stderr

@@ -2,7 +2,7 @@ error: unused import: `a::x`
   --> $DIR/lint-directives-on-use-items-issue-10534.rs:12:9
    |
 LL |     use a::x; //~ ERROR: unused import
-   |     ----^^^^- help: remove the whole `use` item
+   |         ^^^^
    |
 note: lint level defined here
   --> $DIR/lint-directives-on-use-items-issue-10534.rs:1:9
@@ -14,7 +14,7 @@ error: unused import: `a::y`
   --> $DIR/lint-directives-on-use-items-issue-10534.rs:21:9
    |
 LL |     use a::y; //~ ERROR: unused import
-   |     ----^^^^- help: remove the whole `use` item
+   |         ^^^^
    |
 note: lint level defined here
   --> $DIR/lint-directives-on-use-items-issue-10534.rs:20:12

src/test/ui/lint/lint-unused-imports.stderr

@@ -2,7 +2,7 @@ error: unused import: `std::fmt::{}`
   --> $DIR/lint-unused-imports.rs:8:5
    |
 LL | use std::fmt::{};
-   | ----^^^^^^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/lint-unused-imports.rs:1:9
@@ -14,39 +14,37 @@ error: unused imports: `None`, `Some`
   --> $DIR/lint-unused-imports.rs:12:27
    |
 LL | use std::option::Option::{Some, None};
-   | --------------------------^^^^--^^^^-- help: remove the whole `use` item
+   |                           ^^^^  ^^^^
 
 error: unused import: `test::A`
   --> $DIR/lint-unused-imports.rs:15:5
    |
 LL | use test::A;       //~ ERROR unused import: `test::A`
-   | ----^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^
 
 error: unused import: `bar`
   --> $DIR/lint-unused-imports.rs:24:18
    |
 LL | use test2::{foo, bar}; //~ ERROR unused import: `bar`
-   |                --^^^
-   |                |
-   |                help: remove the unused import
+   |                  ^^^
 
 error: unused import: `foo::Square`
   --> $DIR/lint-unused-imports.rs:52:13
    |
 LL |         use foo::Square; //~ ERROR unused import: `foo::Square`
-   |         ----^^^^^^^^^^^- help: remove the whole `use` item
+   |             ^^^^^^^^^^^
 
 error: unused import: `self::g`
   --> $DIR/lint-unused-imports.rs:68:9
    |
 LL |     use self::g; //~ ERROR unused import: `self::g`
-   |     ----^^^^^^^- help: remove the whole `use` item
+   |         ^^^^^^^
 
 error: unused import: `test2::foo`
   --> $DIR/lint-unused-imports.rs:77:9
    |
 LL |     use test2::foo; //~ ERROR unused import: `test2::foo`
-   |     ----^^^^^^^^^^- help: remove the whole `use` item
+   |         ^^^^^^^^^^
 
 error: unused import: `test::B2`
   --> $DIR/lint-unused-imports.rs:20:5

src/test/ui/lint/lints-in-foreign-macros.stderr

@@ -2,7 +2,7 @@ warning: unused import: `std::string::ToString`
   --> $DIR/lints-in-foreign-macros.rs:11:16
    |
 LL |     () => {use std::string::ToString;} //~ WARN: unused import
-   |            ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
+   |                ^^^^^^^^^^^^^^^^^^^^^
 ...
 LL | mod a { foo!(); }
    |         ------- in this macro invocation
@@ -17,13 +17,13 @@ warning: unused import: `std::string::ToString`
   --> $DIR/lints-in-foreign-macros.rs:16:18
    |
 LL | mod c { baz!(use std::string::ToString;); } //~ WARN: unused import
-   |              ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
+   |                  ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused import: `std::string::ToString`
   --> $DIR/lints-in-foreign-macros.rs:17:19
    |
 LL | mod d { baz2!(use std::string::ToString;); } //~ WARN: unused import
-   |               ----^^^^^^^^^^^^^^^^^^^^^- help: remove the whole `use` item
+   |                   ^^^^^^^^^^^^^^^^^^^^^
 
 warning: missing documentation for crate
   --> $DIR/lints-in-foreign-macros.rs:4:1

src/test/ui/rfc-2166-underscore-imports/basic.stderr

@@ -2,7 +2,7 @@ warning: unused import: `m::Tr1 as _`
   --> $DIR/basic.rs:26:9
    |
 LL |     use m::Tr1 as _; //~ WARN unused import
-   |     ----^^^^^^^^^^^- help: remove the whole `use` item
+   |         ^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/basic.rs:4:9
@@ -14,5 +14,5 @@ warning: unused import: `S as _`
   --> $DIR/basic.rs:27:9
    |
 LL |     use S as _; //~ WARN unused import
-   |     ----^^^^^^- help: remove the whole `use` item
+   |         ^^^^^^
 

src/test/ui/rfc-2166-underscore-imports/unused-2018.stderr

@@ -2,7 +2,7 @@ error: unused import: `core::any`
   --> $DIR/unused-2018.rs:6:9
    |
 LL |     use core::any; //~ ERROR unused import: `core::any`
-   |     ----^^^^^^^^^- help: remove the whole `use` item
+   |         ^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/unused-2018.rs:3:9
@@ -14,7 +14,7 @@ error: unused import: `core`
   --> $DIR/unused-2018.rs:10:9
    |
 LL |     use core; //~ ERROR unused import: `core`
-   |     ----^^^^- help: remove the whole `use` item
+   |         ^^^^
 
 error: aborting due to 2 previous errors
 

src/test/ui/span/multispan-import-lint.stderr

@@ -10,8 +10,4 @@ note: lint level defined here
 LL | #![warn(unused)]
    |         ^^^^^^
    = note: #[warn(unused_imports)] implied by #[warn(unused)]
-help: remove the unused imports
-   |
-LL | use std::cmp::{min};
-   |               -- --
 

src/test/ui/use/use-nested-groups-unused-imports.stderr

@@ -2,7 +2,7 @@ error: unused imports: `*`, `Foo`, `baz::{}`, `foobar::*`
   --> $DIR/use-nested-groups-unused-imports.rs:16:11
    |
 LL | use foo::{Foo, bar::{baz::{}, foobar::*}, *};
-   | ----------^^^--------^^^^^^^--^^^^^^^^^---^-- help: remove the whole `use` item
+   |           ^^^        ^^^^^^^  ^^^^^^^^^   ^
    |
 note: lint level defined here
   --> $DIR/use-nested-groups-unused-imports.rs:3:9
@@ -14,15 +14,13 @@ error: unused import: `*`
   --> $DIR/use-nested-groups-unused-imports.rs:18:24
    |
 LL | use foo::bar::baz::{*, *};
-   |                      --^
-   |                      |
-   |                      help: remove the unused import
+   |                        ^
 
 error: unused import: `foo::{}`
   --> $DIR/use-nested-groups-unused-imports.rs:20:5
    |
 LL | use foo::{};
-   | ----^^^^^^^- help: remove the whole `use` item
+   |     ^^^^^^^
 
 error: aborting due to 3 previous errors