3 files changed, 121 insertions, 29 deletions

diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index 1fbb7131d..3d05dd093 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -6,6 +6,7 @@
 
 mod unresolved_module;
 mod unresolved_extern_crate;
+mod unresolved_import;
 mod missing_fields;
 
 mod fixes;
@@ -43,17 +44,39 @@ pub struct Diagnostic {
     pub fixes: Option<Vec<Assist>>,
     pub unused: bool,
     pub code: Option<DiagnosticCode>,
+    pub experimental: bool,
 }
 
 impl Diagnostic {
     fn new(code: &'static str, message: impl Into<String>, range: TextRange) -> Diagnostic {
         let message = message.into();
         let code = Some(DiagnosticCode(code));
-        Self { message, range, severity: Severity::Error, fixes: None, unused: false, code }
+        Self {
+            message,
+            range,
+            severity: Severity::Error,
+            fixes: None,
+            unused: false,
+            code,
+            experimental: false,
+        }
+    }
+
+    fn experimental(mut self) -> Diagnostic {
+        self.experimental = true;
+        self
     }
 
     fn error(range: TextRange, message: String) -> Self {
-        Self { message, range, severity: Severity::Error, fixes: None, unused: false, code: None }
+        Self {
+            message,
+            range,
+            severity: Severity::Error,
+            fixes: None,
+            unused: false,
+            code: None,
+            experimental: false,
+        }
     }
 
     fn hint(range: TextRange, message: String) -> Self {
@@ -64,6 +87,7 @@ impl Diagnostic {
             fixes: None,
             unused: false,
             code: None,
+            experimental: false,
         }
     }
 
@@ -234,6 +258,7 @@ pub(crate) fn diagnostics(
         let d = match diag {
             AnyDiagnostic::UnresolvedModule(d) => unresolved_module::unresolved_module(&ctx, &d),
             AnyDiagnostic::UnresolvedExternCrate(d) => unresolved_extern_crate::unresolved_extern_crate(&ctx, &d),
+            AnyDiagnostic::UnresolvedImport(d) => unresolved_import::unresolved_import(&ctx, &d),
             AnyDiagnostic::MissingFields(d) => missing_fields::missing_fields(&ctx, &d),
         };
         if let Some(code) = d.code {
@@ -241,6 +266,9 @@ pub(crate) fn diagnostics(
                 continue;
             }
         }
+        if ctx.config.disable_experimental && d.experimental {
+            continue;
+        }
         res.push(d)
     }
 
@@ -463,33 +491,6 @@ foo::bar!(92);
     }
 
     #[test]
-    fn unresolved_import_in_use_tree() {
-        // Only the relevant part of a nested `use` item should be highlighted.
-        check_diagnostics(
-            r#"
-use does_exist::{Exists, DoesntExist};
-                       //^^^^^^^^^^^ unresolved import
-
-use {does_not_exist::*, does_exist};
-   //^^^^^^^^^^^^^^^^^ unresolved import
-
-use does_not_exist::{
-    a,
-  //^ unresolved import
-    b,
-  //^ unresolved import
-    c,
-  //^ unresolved import
-};
-
-mod does_exist {
-    pub struct Exists;
-}
-"#,
-        );
-    }
-
-    #[test]
     fn range_mapping_out_of_macros() {
         // FIXME: this is very wrong, but somewhat tricky to fix.
         check_fix(
diff --git a/crates/ide/src/diagnostics/unresolved_import.rs b/crates/ide/src/diagnostics/unresolved_import.rs
new file mode 100644
index 000000000..1cbf96ba1
--- /dev/null
+++ b/crates/ide/src/diagnostics/unresolved_import.rs
@@ -0,0 +1,90 @@
+use crate::diagnostics::{Diagnostic, DiagnosticsContext};
+
+// Diagnostic: unresolved-import
+//
+// This diagnostic is triggered if rust-analyzer is unable to resolve a path in
+// a `use` declaration.
+pub(super) fn unresolved_import(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::UnresolvedImport,
+) -> Diagnostic {
+    Diagnostic::new(
+        "unresolved-import",
+        "unresolved import",
+        ctx.sema.diagnostics_display_range(d.decl.clone().map(|it| it.into())).range,
+    )
+    // This currently results in false positives in the following cases:
+    // - `cfg_if!`-generated code in libstd (we don't load the sysroot correctly)
+    // - `core::arch` (we don't handle `#[path = "../<path>"]` correctly)
+    // - proc macros and/or proc macro generated code
+    .experimental()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::diagnostics::tests::check_diagnostics;
+
+    #[test]
+    fn unresolved_import() {
+        check_diagnostics(
+            r#"
+use does_exist;
+use does_not_exist;
+  //^^^^^^^^^^^^^^ unresolved import
+
+mod does_exist {}
+"#,
+        );
+    }
+
+    #[test]
+    fn unresolved_import_in_use_tree() {
+        // Only the relevant part of a nested `use` item should be highlighted.
+        check_diagnostics(
+            r#"
+use does_exist::{Exists, DoesntExist};
+                       //^^^^^^^^^^^ unresolved import
+
+use {does_not_exist::*, does_exist};
+   //^^^^^^^^^^^^^^^^^ unresolved import
+
+use does_not_exist::{
+    a,
+  //^ unresolved import
+    b,
+  //^ unresolved import
+    c,
+  //^ unresolved import
+};
+
+mod does_exist {
+    pub struct Exists;
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn dedup_unresolved_import_from_unresolved_crate() {
+        check_diagnostics(
+            r#"
+//- /main.rs crate:main
+mod a {
+    extern crate doesnotexist;
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+
+    // Should not error, since we already errored for the missing crate.
+    use doesnotexist::{self, bla, *};
+
+    use crate::doesnotexist;
+      //^^^^^^^^^^^^^^^^^^^ unresolved import
+}
+
+mod m {
+    use super::doesnotexist;
+      //^^^^^^^^^^^^^^^^^^^ unresolved import
+}
+"#,
+        );
+    }
+}
diff --git a/crates/ide/src/diagnostics/unresolved_module.rs b/crates/ide/src/diagnostics/unresolved_module.rs
index 4c8c74ff7..b1da8f0e1 100644
--- a/crates/ide/src/diagnostics/unresolved_module.rs
+++ b/crates/ide/src/diagnostics/unresolved_module.rs
@@ -104,6 +104,7 @@ mod baz {}
                                 "unresolved-module",
                             ),
                         ),
+                        experimental: false,
                     },
                 ]
             "#]],