Workaround the drive letter casing issue on windows.

src/clangd-context.ts

@@ -100,6 +100,34 @@ export class ClangdContext implements vscode.Disposable {
       // Do not switch to output window when clangd returns output.
       revealOutputChannelOn: vscodelc.RevealOutputChannelOn.Never,
 
+      uriConverters: {
+        code2Protocol: (uri: vscode.Uri): string => {
+          if (process.platform === 'win32') {
+
+            if (uri.scheme === 'file') {
+              // https://github.com/clangd/vscode-clangd/issues/726
+              // Remove this workaround once clangd fixes the issue on their side: https://github.com/clangd/clangd/issues/108
+
+              // Fix lower case drive letters on Windows
+              let fsPath = uri.fsPath
+
+              // Extract the drive letter (first two characters, e.g., "c:")
+              const driveLetterMatch = fsPath.match(/^([a-z]):/i);
+
+              if (driveLetterMatch) {
+                // Convert the drive letter to uppercase
+                const driveLetter = driveLetterMatch[1].toUpperCase();
+                // Replace the old drive letter with the new one
+                return "file:///" + fsPath.replace(/^([a-z]):/i, `${driveLetter}:`);
+              }
+
+            }
+          }
+          return uri.toString();
+        },
+        protocol2Code: (uri: string) => vscode.Uri.parse(uri),
+      },
+
       // We hack up the completion items a bit to prevent VSCode from re-ranking
       // and throwing away all our delicious signals like type information.
       //