diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index 04e286780c..789c86a353 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -1,10 +1,6 @@
 //! This module provides the functionality needed to convert diagnostics from
 //! `cargo check` json format to the LSP diagnostic format.
-use std::{
-    collections::HashMap,
-    path::{Component, Path, Prefix},
-    str::FromStr,
-};
+use std::{collections::HashMap, path::Path};
 
 use lsp_types::{
     Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag, Location,
@@ -13,7 +9,7 @@ use lsp_types::{
 use ra_flycheck::{Applicability, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion};
 use stdx::format_to;
 
-use crate::{lsp_ext, Result};
+use crate::{lsp_ext, to_proto::url_from_abs_path};
 
 /// Converts a Rust level string to a LSP severity
 fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
@@ -65,7 +61,7 @@ fn map_span_to_location(span: &DiagnosticSpan, workspace_root: &Path) -> Locatio
 fn map_span_to_location_naive(span: &DiagnosticSpan, workspace_root: &Path) -> Location {
     let mut file_name = workspace_root.to_path_buf();
     file_name.push(&span.file_name);
-    let uri = url_from_path_with_drive_lowercasing(file_name).unwrap();
+    let uri = url_from_abs_path(&file_name);
 
     // FIXME: this doesn't handle UTF16 offsets correctly
     let range = Range::new(
@@ -275,70 +271,16 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
         .collect()
 }
 
-/// Returns a `Url` object from a given path, will lowercase drive letters if present.
-/// This will only happen when processing windows paths.
-///
-/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
-pub fn url_from_path_with_drive_lowercasing(path: impl AsRef<Path>) -> Result<Url> {
-    let component_has_windows_drive = path.as_ref().components().any(|comp| {
-        if let Component::Prefix(c) = comp {
-            return matches!(c.kind(), Prefix::Disk(_) | Prefix::VerbatimDisk(_));
-        }
-        false
-    });
-
-    // VSCode expects drive letters to be lowercased, where rust will uppercase the drive letters.
-    let res = if component_has_windows_drive {
-        let url_original = Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?;
-
-        let drive_partition: Vec<&str> = url_original.as_str().rsplitn(2, ':').collect();
-
-        // There is a drive partition, but we never found a colon.
-        // This should not happen, but in this case we just pass it through.
-        if drive_partition.len() == 1 {
-            return Ok(url_original);
-        }
-
-        let joined = drive_partition[1].to_ascii_lowercase() + ":" + drive_partition[0];
-        let url = Url::from_str(&joined).expect("This came from a valid `Url`");
-
-        url
-    } else {
-        Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.as_ref().display()))?
-    };
-    Ok(res)
-}
-
 #[cfg(test)]
+#[cfg(not(windows))]
 mod tests {
     use super::*;
 
-    // `Url` is not able to parse windows paths on unix machines.
-    #[test]
-    #[cfg(target_os = "windows")]
-    fn test_lowercase_drive_letter_with_drive() {
-        let url = url_from_path_with_drive_lowercasing("C:\\Test").unwrap();
-
-        assert_eq!(url.to_string(), "file:///c:/Test");
-    }
-
-    #[test]
-    #[cfg(target_os = "windows")]
-    fn test_drive_without_colon_passthrough() {
-        let url = url_from_path_with_drive_lowercasing(r#"\\localhost\C$\my_dir"#).unwrap();
-
-        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
-    }
-
-    #[cfg(not(windows))]
     fn parse_diagnostic(val: &str) -> ra_flycheck::Diagnostic {
         serde_json::from_str::<ra_flycheck::Diagnostic>(val).unwrap()
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_incompatible_type_for_trait() {
         let diag = parse_diagnostic(
             r##"{
@@ -392,7 +334,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_unused_variable() {
         let diag = parse_diagnostic(
             r##"{
@@ -475,7 +416,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_wrong_number_of_parameters() {
         let diag = parse_diagnostic(
             r##"{
@@ -600,7 +540,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_clippy_pass_by_ref() {
         let diag = parse_diagnostic(
             r##"{
@@ -721,7 +660,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_rustc_mismatched_type() {
         let diag = parse_diagnostic(
             r##"{
@@ -765,7 +703,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_handles_macro_location() {
         let diag = parse_diagnostic(
             r##"{
@@ -1037,7 +974,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_macro_compiler_error() {
         let diag = parse_diagnostic(
             r##"{
@@ -1267,7 +1203,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(not(windows))]
     fn snap_multi_line_fix() {
         let diag = parse_diagnostic(
             r##"{
diff --git a/crates/rust-analyzer/src/from_proto.rs b/crates/rust-analyzer/src/from_proto.rs
index 206673829c..40f856e6e8 100644
--- a/crates/rust-analyzer/src/from_proto.rs
+++ b/crates/rust-analyzer/src/from_proto.rs
@@ -17,7 +17,7 @@ pub(crate) fn text_range(line_index: &LineIndex, range: lsp_types::Range) -> Tex
 }
 
 pub(crate) fn file_id(world: &GlobalStateSnapshot, url: &lsp_types::Url) -> Result<FileId> {
-    world.uri_to_file_id(url)
+    world.url_to_file_id(url)
 }
 
 pub(crate) fn file_position(
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 21116e165e..9d5685d88e 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -22,10 +22,9 @@ use stdx::format_to;
 
 use crate::{
     config::Config,
-    diagnostics::{
-        to_proto::url_from_path_with_drive_lowercasing, CheckFixes, DiagnosticCollection,
-    },
+    diagnostics::{CheckFixes, DiagnosticCollection},
     main_loop::pending_requests::{CompletedRequest, LatestRequests},
+    to_proto::url_from_abs_path,
     vfs_glob::{Glob, RustPackageFilterBuilder},
     LspError, Result,
 };
@@ -274,8 +273,8 @@ impl GlobalStateSnapshot {
         &self.analysis
     }
 
-    pub fn uri_to_file_id(&self, uri: &Url) -> Result<FileId> {
-        let path = uri.to_file_path().map_err(|()| format!("invalid uri: {}", uri))?;
+    pub fn url_to_file_id(&self, url: &Url) -> Result<FileId> {
+        let path = url.to_file_path().map_err(|()| format!("invalid uri: {}", url))?;
         let file = self.vfs.read().path2file(&path).ok_or_else(|| {
             // Show warning as this file is outside current workspace
             // FIXME: just handle such files, and remove `LspError::UNKNOWN_FILE`.
@@ -287,11 +286,8 @@ impl GlobalStateSnapshot {
         Ok(FileId(file.0))
     }
 
-    pub fn file_id_to_uri(&self, id: FileId) -> Result<Url> {
-        let path = self.vfs.read().file2path(VfsFile(id.0));
-        let url = url_from_path_with_drive_lowercasing(path)?;
-
-        Ok(url)
+    pub fn file_id_to_url(&self, id: FileId) -> Url {
+        file_id_to_url(&self.vfs.read(), id)
     }
 
     pub fn file_id_to_path(&self, id: FileId) -> PathBuf {
@@ -302,12 +298,10 @@ impl GlobalStateSnapshot {
         self.vfs.read().file_line_endings(VfsFile(id.0))
     }
 
-    pub fn path_to_uri(&self, root: SourceRootId, path: &RelativePathBuf) -> Result<Url> {
+    pub fn path_to_url(&self, root: SourceRootId, path: &RelativePathBuf) -> Url {
         let base = self.vfs.read().root2path(VfsRoot(root.0));
         let path = path.to_path(base);
-        let url = Url::from_file_path(&path)
-            .map_err(|_| format!("can't convert path to url: {}", path.display()))?;
-        Ok(url)
+        url_from_abs_path(&path)
     }
 
     pub fn status(&self) -> String {
@@ -335,3 +329,8 @@ impl GlobalStateSnapshot {
         self.workspaces.iter().find_map(|ws| ws.workspace_root_for(&path))
     }
 }
+
+pub(crate) fn file_id_to_url(vfs: &Vfs, id: FileId) -> Url {
+    let path = vfs.file2path(VfsFile(id.0));
+    url_from_abs_path(&path)
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 752dbf1452..8ec571b709 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -27,7 +27,7 @@ use ra_flycheck::{CheckTask, Status};
 use ra_ide::{Canceled, FileId, LibraryData, LineIndex, SourceRootId};
 use ra_prof::profile;
 use ra_project_model::{PackageRoot, ProjectWorkspace};
-use ra_vfs::{VfsFile, VfsTask, Watch};
+use ra_vfs::{VfsTask, Watch};
 use relative_path::RelativePathBuf;
 use rustc_hash::FxHashSet;
 use serde::{de::DeserializeOwned, Serialize};
@@ -35,9 +35,9 @@ use threadpool::ThreadPool;
 
 use crate::{
     config::{Config, FilesWatcher, LinkedProject},
-    diagnostics::{to_proto::url_from_path_with_drive_lowercasing, DiagnosticTask},
+    diagnostics::DiagnosticTask,
     from_proto,
-    global_state::{GlobalState, GlobalStateSnapshot},
+    global_state::{file_id_to_url, GlobalState, GlobalStateSnapshot},
     lsp_ext,
     main_loop::{
         pending_requests::{PendingRequest, PendingRequests},
@@ -801,17 +801,9 @@ fn on_diagnostic_task(task: DiagnosticTask, msg_sender: &Sender<Message>, state:
     let subscriptions = state.diagnostics.handle_task(task);
 
     for file_id in subscriptions {
-        let path = state.vfs.read().file2path(VfsFile(file_id.0));
-        let uri = match url_from_path_with_drive_lowercasing(&path) {
-            Ok(uri) => uri,
-            Err(err) => {
-                log::error!("Couldn't convert path to url ({}): {}", err, path.display());
-                continue;
-            }
-        };
-
+        let url = file_id_to_url(&state.vfs.read(), file_id);
         let diagnostics = state.diagnostics.diagnostics_for(file_id).cloned().collect();
-        let params = lsp_types::PublishDiagnosticsParams { uri, diagnostics, version: None };
+        let params = lsp_types::PublishDiagnosticsParams { uri: url, diagnostics, version: None };
         let not = notification_new::<lsp_types::notification::PublishDiagnostics>(params);
         msg_sender.send(not.into()).unwrap();
     }
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index a41adf8b0b..b34b529b5c 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -258,7 +258,7 @@ pub fn handle_document_symbol(
     let res = if snap.config.client_caps.hierarchical_symbols {
         document_symbols.into()
     } else {
-        let url = to_proto::url(&snap, file_id)?;
+        let url = to_proto::url(&snap, file_id);
         let mut symbol_information = Vec::<SymbolInformation>::new();
         for symbol in document_symbols {
             flatten_document_symbol(&symbol, None, &url, &mut symbol_information);
@@ -1160,7 +1160,7 @@ fn show_impl_command_link(
 ) -> Option<lsp_ext::CommandLinkGroup> {
     if snap.config.hover.implementations {
         if let Some(nav_data) = snap.analysis().goto_implementation(*position).unwrap_or(None) {
-            let uri = to_proto::url(snap, position.file_id).ok()?;
+            let uri = to_proto::url(snap, position.file_id);
             let line_index = snap.analysis().file_line_index(position.file_id).ok()?;
             let position = to_proto::position(&line_index, position.offset);
             let locations: Vec<_> = nav_data
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 710df1fbde..881aa1c55f 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -1,4 +1,7 @@
 //! Conversion of rust-analyzer specific types to lsp_types equivalents.
+use std::path::{self, Path};
+
+use itertools::Itertools;
 use ra_db::{FileId, FileRange};
 use ra_ide::{
     Assist, CompletionItem, CompletionItemKind, Documentation, FileSystemEdit, Fold, FoldKind,
@@ -385,24 +388,55 @@ pub(crate) fn folding_range(
     }
 }
 
-pub(crate) fn url(snap: &GlobalStateSnapshot, file_id: FileId) -> Result<lsp_types::Url> {
-    snap.file_id_to_uri(file_id)
+pub(crate) fn url(snap: &GlobalStateSnapshot, file_id: FileId) -> lsp_types::Url {
+    snap.file_id_to_url(file_id)
+}
+
+/// Returns a `Url` object from a given path, will lowercase drive letters if present.
+/// This will only happen when processing windows paths.
+///
+/// When processing non-windows path, this is essentially the same as `Url::from_file_path`.
+pub(crate) fn url_from_abs_path(path: &Path) -> lsp_types::Url {
+    assert!(path.is_absolute());
+    let url = lsp_types::Url::from_file_path(path).unwrap();
+    match path.components().next() {
+        Some(path::Component::Prefix(prefix)) if matches!(prefix.kind(), path::Prefix::Disk(_) | path::Prefix::VerbatimDisk(_)) =>
+        {
+            // Need to lowercase driver letter
+        }
+        _ => return url,
+    }
+
+    let driver_letter_range = {
+        let (scheme, drive_letter, _rest) = match url.as_str().splitn(3, ':').collect_tuple() {
+            Some(it) => it,
+            None => return url,
+        };
+        let start = scheme.len() + ':'.len_utf8();
+        start..(start + drive_letter.len())
+    };
+
+    // Note: lowercasing the `path` itself doesn't help, the `Url::parse`
+    // machinery *also* canonicalizes the drive letter. So, just massage the
+    // string in place.
+    let mut url = url.into_string();
+    url[driver_letter_range].make_ascii_lowercase();
+    lsp_types::Url::parse(&url).unwrap()
 }
 
 pub(crate) fn versioned_text_document_identifier(
     snap: &GlobalStateSnapshot,
     file_id: FileId,
     version: Option<i64>,
-) -> Result<lsp_types::VersionedTextDocumentIdentifier> {
-    let res = lsp_types::VersionedTextDocumentIdentifier { uri: url(snap, file_id)?, version };
-    Ok(res)
+) -> lsp_types::VersionedTextDocumentIdentifier {
+    lsp_types::VersionedTextDocumentIdentifier { uri: url(snap, file_id), version }
 }
 
 pub(crate) fn location(
     snap: &GlobalStateSnapshot,
     frange: FileRange,
 ) -> Result<lsp_types::Location> {
-    let url = url(snap, frange.file_id)?;
+    let url = url(snap, frange.file_id);
     let line_index = snap.analysis().file_line_index(frange.file_id)?;
     let range = range(&line_index, frange.range);
     let loc = lsp_types::Location::new(url, range);
@@ -438,7 +472,7 @@ fn location_info(
 ) -> Result<(lsp_types::Url, lsp_types::Range, lsp_types::Range)> {
     let line_index = snap.analysis().file_line_index(target.file_id())?;
 
-    let target_uri = url(snap, target.file_id())?;
+    let target_uri = url(snap, target.file_id());
     let target_range = range(&line_index, target.full_range());
     let target_selection_range =
         target.focus_range().map(|it| range(&line_index, it)).unwrap_or(target_range);
@@ -478,7 +512,7 @@ pub(crate) fn snippet_text_document_edit(
     is_snippet: bool,
     source_file_edit: SourceFileEdit,
 ) -> Result<lsp_ext::SnippetTextDocumentEdit> {
-    let text_document = versioned_text_document_identifier(snap, source_file_edit.file_id, None)?;
+    let text_document = versioned_text_document_identifier(snap, source_file_edit.file_id, None);
     let line_index = snap.analysis().file_line_index(source_file_edit.file_id)?;
     let line_endings = snap.file_line_endings(source_file_edit.file_id);
     let edits = source_file_edit
@@ -492,19 +526,18 @@ pub(crate) fn snippet_text_document_edit(
 pub(crate) fn resource_op(
     snap: &GlobalStateSnapshot,
     file_system_edit: FileSystemEdit,
-) -> Result<lsp_types::ResourceOp> {
-    let res = match file_system_edit {
+) -> lsp_types::ResourceOp {
+    match file_system_edit {
         FileSystemEdit::CreateFile { source_root, path } => {
-            let uri = snap.path_to_uri(source_root, &path)?;
+            let uri = snap.path_to_url(source_root, &path);
             lsp_types::ResourceOp::Create(lsp_types::CreateFile { uri, options: None })
         }
         FileSystemEdit::MoveFile { src, dst_source_root, dst_path } => {
-            let old_uri = snap.file_id_to_uri(src)?;
-            let new_uri = snap.path_to_uri(dst_source_root, &dst_path)?;
+            let old_uri = snap.file_id_to_url(src);
+            let new_uri = snap.path_to_url(dst_source_root, &dst_path);
             lsp_types::ResourceOp::Rename(lsp_types::RenameFile { old_uri, new_uri, options: None })
         }
-    };
-    Ok(res)
+    }
 }
 
 pub(crate) fn snippet_workspace_edit(
@@ -513,7 +546,7 @@ pub(crate) fn snippet_workspace_edit(
 ) -> Result<lsp_ext::SnippetWorkspaceEdit> {
     let mut document_changes: Vec<lsp_ext::SnippetDocumentChangeOperation> = Vec::new();
     for op in source_change.file_system_edits {
-        let op = resource_op(&snap, op)?;
+        let op = resource_op(&snap, op);
         document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Op(op));
     }
     for edit in source_change.source_file_edits {
@@ -568,7 +601,7 @@ impl From<lsp_ext::SnippetWorkspaceEdit> for lsp_types::WorkspaceEdit {
     }
 }
 
-pub fn call_hierarchy_item(
+pub(crate) fn call_hierarchy_item(
     snap: &GlobalStateSnapshot,
     target: NavigationTarget,
 ) -> Result<lsp_types::CallHierarchyItem> {
@@ -579,50 +612,6 @@ pub fn call_hierarchy_item(
     Ok(lsp_types::CallHierarchyItem { name, kind, tags: None, detail, uri, range, selection_range })
 }
 
-#[cfg(test)]
-mod tests {
-    use test_utils::extract_ranges;
-
-    use super::*;
-
-    #[test]
-    fn conv_fold_line_folding_only_fixup() {
-        let text = r#"<fold>mod a;
-mod b;
-mod c;</fold>
-
-fn main() <fold>{
-    if cond <fold>{
-        a::do_a();
-    }</fold> else <fold>{
-        b::do_b();
-    }</fold>
-}</fold>"#;
-
-        let (ranges, text) = extract_ranges(text, "fold");
-        assert_eq!(ranges.len(), 4);
-        let folds = vec![
-            Fold { range: ranges[0], kind: FoldKind::Mods },
-            Fold { range: ranges[1], kind: FoldKind::Block },
-            Fold { range: ranges[2], kind: FoldKind::Block },
-            Fold { range: ranges[3], kind: FoldKind::Block },
-        ];
-
-        let line_index = LineIndex::new(&text);
-        let converted: Vec<lsp_types::FoldingRange> =
-            folds.into_iter().map(|it| folding_range(&text, &line_index, true, it)).collect();
-
-        let expected_lines = [(0, 2), (4, 10), (5, 6), (7, 9)];
-        assert_eq!(converted.len(), expected_lines.len());
-        for (folding_range, (start_line, end_line)) in converted.iter().zip(expected_lines.iter()) {
-            assert_eq!(folding_range.start_line, *start_line);
-            assert_eq!(folding_range.start_character, None);
-            assert_eq!(folding_range.end_line, *end_line);
-            assert_eq!(folding_range.end_character, None);
-        }
-    }
-}
-
 pub(crate) fn unresolved_code_action(
     snap: &GlobalStateSnapshot,
     assist: Assist,
@@ -676,3 +665,62 @@ pub(crate) fn runnable(
         },
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use test_utils::extract_ranges;
+
+    use super::*;
+
+    #[test]
+    fn conv_fold_line_folding_only_fixup() {
+        let text = r#"<fold>mod a;
+mod b;
+mod c;</fold>
+
+fn main() <fold>{
+    if cond <fold>{
+        a::do_a();
+    }</fold> else <fold>{
+        b::do_b();
+    }</fold>
+}</fold>"#;
+
+        let (ranges, text) = extract_ranges(text, "fold");
+        assert_eq!(ranges.len(), 4);
+        let folds = vec![
+            Fold { range: ranges[0], kind: FoldKind::Mods },
+            Fold { range: ranges[1], kind: FoldKind::Block },
+            Fold { range: ranges[2], kind: FoldKind::Block },
+            Fold { range: ranges[3], kind: FoldKind::Block },
+        ];
+
+        let line_index = LineIndex::new(&text);
+        let converted: Vec<lsp_types::FoldingRange> =
+            folds.into_iter().map(|it| folding_range(&text, &line_index, true, it)).collect();
+
+        let expected_lines = [(0, 2), (4, 10), (5, 6), (7, 9)];
+        assert_eq!(converted.len(), expected_lines.len());
+        for (folding_range, (start_line, end_line)) in converted.iter().zip(expected_lines.iter()) {
+            assert_eq!(folding_range.start_line, *start_line);
+            assert_eq!(folding_range.start_character, None);
+            assert_eq!(folding_range.end_line, *end_line);
+            assert_eq!(folding_range.end_character, None);
+        }
+    }
+
+    // `Url` is not able to parse windows paths on unix machines.
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_lowercase_drive_letter_with_drive() {
+        let url = url_from_abs_path(Path::new("C:\\Test"));
+        assert_eq!(url.to_string(), "file:///c:/Test");
+    }
+
+    #[test]
+    #[cfg(target_os = "windows")]
+    fn test_drive_without_colon_passthrough() {
+        let url = url_from_abs_path(Path::new(r#"\\localhost\C$\my_dir"#));
+        assert_eq!(url.to_string(), "file://localhost/C$/my_dir");
+    }
+}