Handle diagnostics with multiple primary spans

11 files changed, 554 insertions, 527 deletions

diff --git a/crates/ra_cargo_watch/src/conv.rs b/crates/ra_cargo_watch/src/conv.rs
index a3f05bede..c6f8ca329 100644
--- a/crates/ra_cargo_watch/src/conv.rs
+++ b/crates/ra_cargo_watch/src/conv.rs
@@ -180,13 +180,13 @@ pub(crate) struct MappedRustDiagnostic {
 pub(crate) fn map_rust_diagnostic_to_lsp(
     rd: &RustDiagnostic,
     workspace_root: &PathBuf,
-) -> Option<MappedRustDiagnostic> {
-    let primary_span = rd.spans.iter().find(|s| s.is_primary)?;
-
-    let location = map_span_to_location(&primary_span, workspace_root);
+) -> Vec<MappedRustDiagnostic> {
+    let primary_spans: Vec<&DiagnosticSpan> = rd.spans.iter().filter(|s| s.is_primary).collect();
+    if primary_spans.is_empty() {
+        return vec![];
+    }
 
     let severity = map_level_to_severity(rd.level);
-    let mut primary_span_label = primary_span.label.as_ref();
 
     let mut source = String::from("rustc");
     let mut code = rd.code.as_ref().map(|c| c.code.clone());
@@ -199,19 +199,10 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
         }
     }
 
+    let mut needs_primary_span_label = true;
     let mut related_information = vec![];
     let mut tags = vec![];
 
-    // If error occurs from macro expansion, add related info pointing to
-    // where the error originated
-    if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
-        let def_loc = map_span_to_location_naive(&primary_span, workspace_root);
-        related_information.push(DiagnosticRelatedInformation {
-            location: def_loc,
-            message: "Error originated from macro here".to_string(),
-        });
-    }
-
     for secondary_span in rd.spans.iter().filter(|s| !s.is_primary) {
         let related = map_secondary_span_to_related(secondary_span, workspace_root);
         if let Some(related) = related {
@@ -231,15 +222,11 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
 
                 // These secondary messages usually duplicate the content of the
                 // primary span label.
-                primary_span_label = None;
+                needs_primary_span_label = false;
             }
         }
     }
 
-    if let Some(primary_span_label) = primary_span_label {
-        write!(&mut message, "\n{}", primary_span_label).unwrap();
-    }
-
     if is_unused_or_unnecessary(rd) {
         tags.push(DiagnosticTag::Unnecessary);
     }
@@ -248,21 +235,45 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
         tags.push(DiagnosticTag::Deprecated);
     }
 
-    let diagnostic = Diagnostic {
-        range: location.range,
-        severity,
-        code: code.map(NumberOrString::String),
-        source: Some(source),
-        message,
-        related_information: if !related_information.is_empty() {
-            Some(related_information)
-        } else {
-            None
-        },
-        tags: if !tags.is_empty() { Some(tags) } else { None },
-    };
-
-    Some(MappedRustDiagnostic { location, diagnostic, fixes })
+    primary_spans
+        .iter()
+        .map(|primary_span| {
+            let location = map_span_to_location(&primary_span, workspace_root);
+
+            let mut message = message.clone();
+            if needs_primary_span_label {
+                if let Some(primary_span_label) = &primary_span.label {
+                    write!(&mut message, "\n{}", primary_span_label).unwrap();
+                }
+            }
+
+            // If error occurs from macro expansion, add related info pointing to
+            // where the error originated
+            if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
+                let def_loc = map_span_to_location_naive(&primary_span, workspace_root);
+                related_information.push(DiagnosticRelatedInformation {
+                    location: def_loc,
+                    message: "Error originated from macro here".to_string(),
+                });
+            }
+
+            let diagnostic = Diagnostic {
+                range: location.range,
+                severity,
+                code: code.clone().map(NumberOrString::String),
+                source: Some(source.clone()),
+                message,
+                related_information: if !related_information.is_empty() {
+                    Some(related_information.clone())
+                } else {
+                    None
+                },
+                tags: if !tags.is_empty() { Some(tags.clone()) } else { None },
+            };
+
+            MappedRustDiagnostic { location, diagnostic, fixes: fixes.clone() }
+        })
+        .collect()
 }
 
 /// Returns a `Url` object from a given path, will lowercase drive letters if present.
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
index 47801ae79..9e8f4eff4 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_clippy_pass_by_ref.snap
@@ -2,98 +2,100 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/compiler/mir/tagset.rs",
-        range: Range {
-            start: Position {
-                line: 41,
-                character: 23,
-            },
-            end: Position {
-                line: 41,
-                character: 28,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/compiler/mir/tagset.rs",
+            range: Range {
+                start: Position {
+                    line: 41,
+                    character: 23,
+                },
+                end: Position {
+                    line: 41,
+                    character: 28,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 41,
-                character: 23,
-            },
-            end: Position {
-                line: 41,
-                character: 28,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 41,
+                    character: 23,
+                },
+                end: Position {
+                    line: 41,
+                    character: 28,
+                },
             },
-        },
-        severity: Some(
-            Warning,
-        ),
-        code: Some(
-            String(
-                "trivially_copy_pass_by_ref",
+            severity: Some(
+                Warning,
             ),
-        ),
-        source: Some(
-            "clippy",
-        ),
-        message: "this argument is passed by reference, but would be more efficient if passed by value\n#[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]\nfor further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref",
-        related_information: Some(
-            [
-                DiagnosticRelatedInformation {
-                    location: Location {
-                        uri: "file:///test/compiler/lib.rs",
-                        range: Range {
-                            start: Position {
-                                line: 0,
-                                character: 8,
-                            },
-                            end: Position {
-                                line: 0,
-                                character: 19,
+            code: Some(
+                String(
+                    "trivially_copy_pass_by_ref",
+                ),
+            ),
+            source: Some(
+                "clippy",
+            ),
+            message: "this argument is passed by reference, but would be more efficient if passed by value\n#[warn(clippy::trivially_copy_pass_by_ref)] implied by #[warn(clippy::all)]\nfor further information visit https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: "file:///test/compiler/lib.rs",
+                            range: Range {
+                                start: Position {
+                                    line: 0,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 0,
+                                    character: 19,
+                                },
                             },
                         },
+                        message: "lint level defined here",
                     },
-                    message: "lint level defined here",
-                },
-            ],
-        ),
-        tags: None,
-    },
-    fixes: [
-        CodeAction {
-            title: "consider passing by value instead",
-            kind: Some(
-                "quickfix",
+                ],
             ),
-            diagnostics: None,
-            edit: Some(
-                WorkspaceEdit {
-                    changes: Some(
-                        {
-                            "file:///test/compiler/mir/tagset.rs": [
-                                TextEdit {
-                                    range: Range {
-                                        start: Position {
-                                            line: 41,
-                                            character: 23,
-                                        },
-                                        end: Position {
-                                            line: 41,
-                                            character: 28,
+            tags: None,
+        },
+        fixes: [
+            CodeAction {
+                title: "consider passing by value instead",
+                kind: Some(
+                    "quickfix",
+                ),
+                diagnostics: None,
+                edit: Some(
+                    WorkspaceEdit {
+                        changes: Some(
+                            {
+                                "file:///test/compiler/mir/tagset.rs": [
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 41,
+                                                character: 23,
+                                            },
+                                            end: Position {
+                                                line: 41,
+                                                character: 28,
+                                            },
                                         },
+                                        new_text: "self",
                                     },
-                                    new_text: "self",
-                                },
-                            ],
-                        },
-                    ),
-                    document_changes: None,
-                },
-            ),
-            command: None,
-            is_preferred: None,
-        },
-    ],
-}
+                                ],
+                            },
+                        ),
+                        document_changes: None,
+                    },
+                ),
+                command: None,
+                is_preferred: None,
+            },
+        ],
+    },
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
index 12eb32df4..61ae0c9ae 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_handles_macro_location.snap
@@ -2,45 +2,47 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/src/main.rs",
-        range: Range {
-            start: Position {
-                line: 1,
-                character: 4,
-            },
-            end: Position {
-                line: 1,
-                character: 26,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/src/main.rs",
+            range: Range {
+                start: Position {
+                    line: 1,
+                    character: 4,
+                },
+                end: Position {
+                    line: 1,
+                    character: 26,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 1,
-                character: 4,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 1,
+                    character: 4,
+                },
+                end: Position {
+                    line: 1,
+                    character: 26,
+                },
             },
-            end: Position {
-                line: 1,
-                character: 26,
-            },
-        },
-        severity: Some(
-            Error,
-        ),
-        code: Some(
-            String(
-                "E0277",
+            severity: Some(
+                Error,
             ),
-        ),
-        source: Some(
-            "rustc",
-        ),
-        message: "can\'t compare `{integer}` with `&str`\nthe trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`",
-        related_information: None,
-        tags: None,
+            code: Some(
+                String(
+                    "E0277",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "can\'t compare `{integer}` with `&str`\nthe trait `std::cmp::PartialEq<&str>` is not implemented for `{integer}`",
+            related_information: None,
+            tags: None,
+        },
+        fixes: [],
     },
-    fixes: [],
-}
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
index 7b83a7cd0..641da1a58 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_macro_compiler_error.snap
@@ -2,60 +2,62 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/crates/ra_hir_def/src/data.rs",
-        range: Range {
-            start: Position {
-                line: 79,
-                character: 15,
-            },
-            end: Position {
-                line: 79,
-                character: 41,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/crates/ra_hir_def/src/data.rs",
+            range: Range {
+                start: Position {
+                    line: 79,
+                    character: 15,
+                },
+                end: Position {
+                    line: 79,
+                    character: 41,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 79,
-                character: 15,
-            },
-            end: Position {
-                line: 79,
-                character: 41,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 79,
+                    character: 15,
+                },
+                end: Position {
+                    line: 79,
+                    character: 41,
+                },
             },
-        },
-        severity: Some(
-            Error,
-        ),
-        code: None,
-        source: Some(
-            "rustc",
-        ),
-        message: "Please register your known path in the path module",
-        related_information: Some(
-            [
-                DiagnosticRelatedInformation {
-                    location: Location {
-                        uri: "file:///test/crates/ra_hir_def/src/path.rs",
-                        range: Range {
-                            start: Position {
-                                line: 264,
-                                character: 8,
-                            },
-                            end: Position {
-                                line: 264,
-                                character: 76,
+            severity: Some(
+                Error,
+            ),
+            code: None,
+            source: Some(
+                "rustc",
+            ),
+            message: "Please register your known path in the path module",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: "file:///test/crates/ra_hir_def/src/path.rs",
+                            range: Range {
+                                start: Position {
+                                    line: 264,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 264,
+                                    character: 76,
+                                },
                             },
                         },
+                        message: "Error originated from macro here",
                     },
-                    message: "Error originated from macro here",
-                },
-            ],
-        ),
-        tags: None,
+                ],
+            ),
+            tags: None,
+        },
+        fixes: [],
     },
-    fixes: [],
-}
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap
index 23c4f5a2c..0557a2e79 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_multi_line_fix.snap
@@ -2,111 +2,113 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/src/main.rs",
-        range: Range {
-            start: Position {
-                line: 3,
-                character: 4,
-            },
-            end: Position {
-                line: 3,
-                character: 5,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/src/main.rs",
+            range: Range {
+                start: Position {
+                    line: 3,
+                    character: 4,
+                },
+                end: Position {
+                    line: 3,
+                    character: 5,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 3,
-                character: 4,
-            },
-            end: Position {
-                line: 3,
-                character: 5,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 3,
+                    character: 4,
+                },
+                end: Position {
+                    line: 3,
+                    character: 5,
+                },
             },
-        },
-        severity: Some(
-            Warning,
-        ),
-        code: Some(
-            String(
-                "let_and_return",
+            severity: Some(
+                Warning,
             ),
-        ),
-        source: Some(
-            "clippy",
-        ),
-        message: "returning the result of a let binding from a block\n`#[warn(clippy::let_and_return)]` on by default\nfor further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return",
-        related_information: Some(
-            [
-                DiagnosticRelatedInformation {
-                    location: Location {
-                        uri: "file:///test/src/main.rs",
-                        range: Range {
-                            start: Position {
-                                line: 2,
-                                character: 4,
-                            },
-                            end: Position {
-                                line: 2,
-                                character: 30,
+            code: Some(
+                String(
+                    "let_and_return",
+                ),
+            ),
+            source: Some(
+                "clippy",
+            ),
+            message: "returning the result of a let binding from a block\n`#[warn(clippy::let_and_return)]` on by default\nfor further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: "file:///test/src/main.rs",
+                            range: Range {
+                                start: Position {
+                                    line: 2,
+                                    character: 4,
+                                },
+                                end: Position {
+                                    line: 2,
+                                    character: 30,
+                                },
                             },
                         },
+                        message: "unnecessary let binding",
                     },
-                    message: "unnecessary let binding",
-                },
-            ],
-        ),
-        tags: None,
-    },
-    fixes: [
-        CodeAction {
-            title: "return the expression directly",
-            kind: Some(
-                "quickfix",
+                ],
             ),
-            diagnostics: None,
-            edit: Some(
-                WorkspaceEdit {
-                    changes: Some(
-                        {
-                            "file:///test/src/main.rs": [
-                                TextEdit {
-                                    range: Range {
-                                        start: Position {
-                                            line: 2,
-                                            character: 4,
-                                        },
-                                        end: Position {
-                                            line: 2,
-                                            character: 30,
+            tags: None,
+        },
+        fixes: [
+            CodeAction {
+                title: "return the expression directly",
+                kind: Some(
+                    "quickfix",
+                ),
+                diagnostics: None,
+                edit: Some(
+                    WorkspaceEdit {
+                        changes: Some(
+                            {
+                                "file:///test/src/main.rs": [
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 2,
+                                                character: 4,
+                                            },
+                                            end: Position {
+                                                line: 2,
+                                                character: 30,
+                                            },
                                         },
+                                        new_text: "",
                                     },
-                                    new_text: "",
-                                },
-                                TextEdit {
-                                    range: Range {
-                                        start: Position {
-                                            line: 3,
-                                            character: 4,
-                                        },
-                                        end: Position {
-                                            line: 3,
-                                            character: 5,
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 3,
+                                                character: 4,
+                                            },
+                                            end: Position {
+                                                line: 3,
+                                                character: 5,
+                                            },
                                         },
+                                        new_text: "(0..10).collect()",
                                     },
-                                    new_text: "(0..10).collect()",
-                                },
-                            ],
-                        },
-                    ),
-                    document_changes: None,
-                },
-            ),
-            command: None,
-            is_preferred: None,
-        },
-    ],
-}
+                                ],
+                            },
+                        ),
+                        document_changes: None,
+                    },
+                ),
+                command: None,
+                is_preferred: None,
+            },
+        ],
+    },
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
index 54679c5db..754bc33a4 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_incompatible_type_for_trait.snap
@@ -2,45 +2,47 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/compiler/ty/list_iter.rs",
-        range: Range {
-            start: Position {
-                line: 51,
-                character: 4,
-            },
-            end: Position {
-                line: 51,
-                character: 47,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/compiler/ty/list_iter.rs",
+            range: Range {
+                start: Position {
+                    line: 51,
+                    character: 4,
+                },
+                end: Position {
+                    line: 51,
+                    character: 47,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 51,
-                character: 4,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 51,
+                    character: 4,
+                },
+                end: Position {
+                    line: 51,
+                    character: 47,
+                },
             },
-            end: Position {
-                line: 51,
-                character: 47,
-            },
-        },
-        severity: Some(
-            Error,
-        ),
-        code: Some(
-            String(
-                "E0053",
+            severity: Some(
+                Error,
             ),
-        ),
-        source: Some(
-            "rustc",
-        ),
-        message: "method `next` has an incompatible type for trait\nexpected type `fn(&mut ty::list_iter::ListIterator<\'list, M>) -> std::option::Option<&ty::Ref<M>>`\n   found type `fn(&ty::list_iter::ListIterator<\'list, M>) -> std::option::Option<&\'list ty::Ref<M>>`",
-        related_information: None,
-        tags: None,
+            code: Some(
+                String(
+                    "E0053",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "method `next` has an incompatible type for trait\nexpected type `fn(&mut ty::list_iter::ListIterator<\'list, M>) -> std::option::Option<&ty::Ref<M>>`\n   found type `fn(&ty::list_iter::ListIterator<\'list, M>) -> std::option::Option<&\'list ty::Ref<M>>`",
+            related_information: None,
+            tags: None,
+        },
+        fixes: [],
     },
-    fixes: [],
-}
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
index 57df4ceaf..78b7f7cc8 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_mismatched_type.snap
@@ -2,45 +2,47 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/runtime/compiler_support.rs",
-        range: Range {
-            start: Position {
-                line: 47,
-                character: 64,
-            },
-            end: Position {
-                line: 47,
-                character: 69,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/runtime/compiler_support.rs",
+            range: Range {
+                start: Position {
+                    line: 47,
+                    character: 64,
+                },
+                end: Position {
+                    line: 47,
+                    character: 69,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 47,
-                character: 64,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 47,
+                    character: 64,
+                },
+                end: Position {
+                    line: 47,
+                    character: 69,
+                },
             },
-            end: Position {
-                line: 47,
-                character: 69,
-            },
-        },
-        severity: Some(
-            Error,
-        ),
-        code: Some(
-            String(
-                "E0308",
+            severity: Some(
+                Error,
             ),
-        ),
-        source: Some(
-            "rustc",
-        ),
-        message: "mismatched types\nexpected usize, found u32",
-        related_information: None,
-        tags: None,
+            code: Some(
+                String(
+                    "E0308",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "mismatched types\nexpected usize, found u32",
+            related_information: None,
+            tags: None,
+        },
+        fixes: [],
     },
-    fixes: [],
-}
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
index 8bab09540..5989ed202 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_unused_variable.snap
@@ -2,83 +2,85 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/driver/subcommand/repl.rs",
-        range: Range {
-            start: Position {
-                line: 290,
-                character: 8,
-            },
-            end: Position {
-                line: 290,
-                character: 11,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/driver/subcommand/repl.rs",
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 290,
-                character: 8,
-            },
-            end: Position {
-                line: 290,
-                character: 11,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 290,
+                    character: 8,
+                },
+                end: Position {
+                    line: 290,
+                    character: 11,
+                },
             },
-        },
-        severity: Some(
-            Warning,
-        ),
-        code: Some(
-            String(
-                "unused_variables",
+            severity: Some(
+                Warning,
             ),
-        ),
-        source: Some(
-            "rustc",
-        ),
-        message: "unused variable: `foo`\n#[warn(unused_variables)] on by default",
-        related_information: None,
-        tags: Some(
-            [
-                Unnecessary,
-            ],
-        ),
-    },
-    fixes: [
-        CodeAction {
-            title: "consider prefixing with an underscore",
-            kind: Some(
-                "quickfix",
+            code: Some(
+                String(
+                    "unused_variables",
+                ),
             ),
-            diagnostics: None,
-            edit: Some(
-                WorkspaceEdit {
-                    changes: Some(
-                        {
-                            "file:///test/driver/subcommand/repl.rs": [
-                                TextEdit {
-                                    range: Range {
-                                        start: Position {
-                                            line: 290,
-                                            character: 8,
-                                        },
-                                        end: Position {
-                                            line: 290,
-                                            character: 11,
-                                        },
-                                    },
-                                    new_text: "_foo",
-                                },
-                            ],
-                        },
-                    ),
-                    document_changes: None,
-                },
+            source: Some(
+                "rustc",
+            ),
+            message: "unused variable: `foo`\n#[warn(unused_variables)] on by default",
+            related_information: None,
+            tags: Some(
+                [
+                    Unnecessary,
+                ],
             ),
-            command: None,
-            is_preferred: None,
         },
-    ],
-}
+        fixes: [
+            CodeAction {
+                title: "consider prefixing with an underscore",
+                kind: Some(
+                    "quickfix",
+                ),
+                diagnostics: None,
+                edit: Some(
+                    WorkspaceEdit {
+                        changes: Some(
+                            {
+                                "file:///test/driver/subcommand/repl.rs": [
+                                    TextEdit {
+                                        range: Range {
+                                            start: Position {
+                                                line: 290,
+                                                character: 8,
+                                            },
+                                            end: Position {
+                                                line: 290,
+                                                character: 11,
+                                            },
+                                        },
+                                        new_text: "_foo",
+                                    },
+                                ],
+                            },
+                        ),
+                        document_changes: None,
+                    },
+                ),
+                command: None,
+                is_preferred: None,
+            },
+        ],
+    },
+]
diff --git a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
index 69301078d..e34b546dc 100644
--- a/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
+++ b/crates/ra_cargo_watch/src/conv/snapshots/ra_cargo_watch__conv__test__snap_rustc_wrong_number_of_parameters.snap
@@ -2,64 +2,66 @@
 source: crates/ra_cargo_watch/src/conv/test.rs
 expression: diag
 ---
-MappedRustDiagnostic {
-    location: Location {
-        uri: "file:///test/compiler/ty/select.rs",
-        range: Range {
-            start: Position {
-                line: 103,
-                character: 17,
-            },
-            end: Position {
-                line: 103,
-                character: 29,
+[
+    MappedRustDiagnostic {
+        location: Location {
+            uri: "file:///test/compiler/ty/select.rs",
+            range: Range {
+                start: Position {
+                    line: 103,
+                    character: 17,
+                },
+                end: Position {
+                    line: 103,
+                    character: 29,
+                },
             },
         },
-    },
-    diagnostic: Diagnostic {
-        range: Range {
-            start: Position {
-                line: 103,
-                character: 17,
-            },
-            end: Position {
-                line: 103,
-                character: 29,
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 103,
+                    character: 17,
+                },
+                end: Position {
+                    line: 103,
+                    character: 29,
+                },
             },
-        },
-        severity: Some(
-            Error,
-        ),
-        code: Some(
-            String(
-                "E0061",
+            severity: Some(
+                Error,
             ),
-        ),
-        source: Some(
-            "rustc",
-        ),
-        message: "this function takes 2 parameters but 3 parameters were supplied\nexpected 2 parameters",
-        related_information: Some(
-            [
-                DiagnosticRelatedInformation {
-                    location: Location {
-                        uri: "file:///test/compiler/ty/select.rs",
-                        range: Range {
-                            start: Position {
-                                line: 218,
-                                character: 4,
-                            },
-                            end: Position {
-                                line: 230,
-                                character: 5,
+            code: Some(
+                String(
+                    "E0061",
+                ),
+            ),
+            source: Some(
+                "rustc",
+            ),
+            message: "this function takes 2 parameters but 3 parameters were supplied\nexpected 2 parameters",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: "file:///test/compiler/ty/select.rs",
+                            range: Range {
+                                start: Position {
+                                    line: 218,
+                                    character: 4,
+                                },
+                                end: Position {
+                                    line: 230,
+                                    character: 5,
+                                },
                             },
                         },
+                        message: "defined here",
                     },
-                    message: "defined here",
-                },
-            ],
-        ),
-        tags: None,
+                ],
+            ),
+            tags: None,
+        },
+        fixes: [],
     },
-    fixes: [],
-}
+]
diff --git a/crates/ra_cargo_watch/src/conv/test.rs b/crates/ra_cargo_watch/src/conv/test.rs
index c880dcdc3..4e81455ca 100644
--- a/crates/ra_cargo_watch/src/conv/test.rs
+++ b/crates/ra_cargo_watch/src/conv/test.rs
@@ -58,7 +58,7 @@ fn snap_rustc_incompatible_type_for_trait() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -141,7 +141,7 @@ fn snap_rustc_unused_variable() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -266,7 +266,7 @@ fn snap_rustc_wrong_number_of_parameters() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -387,7 +387,7 @@ fn snap_clippy_pass_by_ref() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -431,7 +431,7 @@ fn snap_rustc_mismatched_type() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -703,7 +703,7 @@ fn snap_handles_macro_location() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -933,7 +933,7 @@ fn snap_macro_compiler_error() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
 
@@ -1067,6 +1067,6 @@ fn snap_multi_line_fix() {
     );
 
     let workspace_root = PathBuf::from("/test/");
-    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root).expect("couldn't map diagnostic");
+    let diag = map_rust_diagnostic_to_lsp(&diag, &workspace_root);
     insta::assert_debug_snapshot!(diag);
 }
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
index f07c34549..94b9c03d0 100644
--- a/crates/ra_cargo_watch/src/lib.rs
+++ b/crates/ra_cargo_watch/src/lib.rs
@@ -197,23 +197,23 @@ impl CheckWatcherThread {
             }
 
             CheckEvent::Msg(Message::CompilerMessage(msg)) => {
-                let map_result =
-                    match map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root) {
-                        Some(map_result) => map_result,
-                        None => return,
-                    };
-
-                let MappedRustDiagnostic { location, diagnostic, fixes } = map_result;
-                let fixes = fixes
-                    .into_iter()
-                    .map(|fix| {
-                        CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
-                    })
-                    .collect();
+                let map_result = map_rust_diagnostic_to_lsp(&msg.message, &self.workspace_root);
+                if map_result.is_empty() {
+                    return;
+                }
 
-                task_send
-                    .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
-                    .unwrap();
+                for MappedRustDiagnostic { location, diagnostic, fixes } in map_result {
+                    let fixes = fixes
+                        .into_iter()
+                        .map(|fix| {
+                            CodeAction { diagnostics: Some(vec![diagnostic.clone()]), ..fix }.into()
+                        })
+                        .collect();
+
+                    task_send
+                        .send(CheckTask::AddDiagnostic { url: location.uri, diagnostic, fixes })
+                        .unwrap();
+                }
             }
 
             CheckEvent::Msg(Message::BuildScriptExecuted(_msg)) => {}