diff --git a/internal/lsp/cache/check.go b/internal/lsp/cache/check.go
index 5f8d57e0d3..d14e2346f6 100644
--- a/internal/lsp/cache/check.go
+++ b/internal/lsp/cache/check.go
@@ -331,6 +331,19 @@ func typeCheck(ctx context.Context, fset *token.FileSet, m *metadata, mode sourc
 		// race to Unsafe.completed.
 		return pkg, nil
 	} else if len(files) == 0 { // not the unsafe package, no parsed files
+		// Try to attach errors messages to the file as much as possible.
+		var found bool
+		for _, e := range rawErrors {
+			srcErr, err := sourceError(ctx, fset, pkg, e)
+			if err != nil {
+				continue
+			}
+			found = true
+			pkg.errors = append(pkg.errors, srcErr)
+		}
+		if found {
+			return pkg, nil
+		}
 		return nil, errors.Errorf("no parsed files for package %s, expected: %s, errors: %v, list errors: %v", pkg.pkgPath, pkg.compiledGoFiles, actualErrors, rawErrors)
 	} else {
 		pkg.types = types.NewPackage(string(m.pkgPath), string(m.name))
diff --git a/internal/lsp/cache/errors.go b/internal/lsp/cache/errors.go
index eff1c80728..a2d034fd0c 100644
--- a/internal/lsp/cache/errors.go
+++ b/internal/lsp/cache/errors.go
@@ -208,30 +208,29 @@ func typeErrorRange(ctx context.Context, fset *token.FileSet, pkg *pkg, pos toke
 }
 
 func scannerErrorRange(fset *token.FileSet, pkg *pkg, posn token.Position) (span.Span, error) {
-	ph, _, err := source.FindFileInPackage(pkg, span.URIFromPath(posn.Filename))
+	pgh, _, err := source.FindFileInPackage(pkg, span.URIFromPath(posn.Filename))
 	if err != nil {
 		return span.Span{}, err
 	}
-	file, _, _, _, err := ph.Cached()
-	if err != nil {
-		return span.Span{}, err
+	data, err := pgh.(*parseGoHandle).cached()
+	if data.tok == nil {
+		if err != nil {
+			return span.Span{}, err
+		}
+		return span.Span{}, errors.Errorf("no token.File for %s: %v", pgh.File().URI(), data.err)
 	}
-	tok := fset.File(file.Pos())
-	if tok == nil {
-		return span.Span{}, errors.Errorf("no token.File for %s", ph.File().URI())
-	}
-	pos := tok.Pos(posn.Offset)
+	pos := data.tok.Pos(posn.Offset)
 	return span.NewRange(fset, pos, pos).Span()
 }
 
 // spanToRange converts a span.Span to a protocol.Range,
 // assuming that the span belongs to the package whose diagnostics are being computed.
 func spanToRange(pkg *pkg, spn span.Span) (protocol.Range, error) {
-	ph, _, err := source.FindFileInPackage(pkg, spn.URI())
+	pgh, _, err := source.FindFileInPackage(pkg, spn.URI())
 	if err != nil {
 		return protocol.Range{}, err
 	}
-	_, _, m, _, err := ph.Cached()
+	_, _, m, _, err := pgh.Cached()
 	if err != nil {
 		return protocol.Range{}, err
 	}
diff --git a/internal/lsp/cache/parse.go b/internal/lsp/cache/parse.go
index 75d8888cfe..45ca298493 100644
--- a/internal/lsp/cache/parse.go
+++ b/internal/lsp/cache/parse.go
@@ -43,6 +43,7 @@ type parseGoData struct {
 	memoize.NoCopy
 
 	ast    *ast.File
+	tok    *token.File
 	mapper *protocol.ColumnMapper
 
 	// Source code used to build the AST. It may be different from the
@@ -112,12 +113,20 @@ func (pgh *parseGoHandle) parse(ctx context.Context) (*parseGoData, error) {
 }
 
 func (pgh *parseGoHandle) Cached() (*ast.File, []byte, *protocol.ColumnMapper, error, error) {
+	data, err := pgh.cached()
+	if err != nil {
+		return nil, nil, nil, nil, err
+	}
+	return data.ast, data.src, data.mapper, data.parseError, data.err
+}
+
+func (pgh *parseGoHandle) cached() (*parseGoData, error) {
 	v := pgh.handle.Cached()
 	if v == nil {
-		return nil, nil, nil, nil, errors.Errorf("no cached AST for %s", pgh.file.URI())
+		return nil, errors.Errorf("no cached AST for %s", pgh.file.URI())
 	}
 	data := v.(*parseGoData)
-	return data.ast, data.src, data.mapper, data.parseError, data.err
+	return data, nil
 }
 
 func (pgh *parseGoHandle) PosToDecl(ctx context.Context) (map[token.Pos]ast.Decl, error) {
@@ -278,7 +287,19 @@ func parseGo(ctx context.Context, fset *token.FileSet, fh source.FileHandle, mod
 	if file != nil {
 		tok = fset.File(file.Pos())
 		if tok == nil {
-			return &parseGoData{err: errors.Errorf("successfully parsed but no token.File for %s (%v)", fh.URI(), parseError)}
+			tok = fset.AddFile(fh.URI().Filename(), -1, len(buf))
+			tok.SetLinesForContent(buf)
+			return &parseGoData{
+				ast: file,
+				src: buf,
+				tok: tok,
+				mapper: &protocol.ColumnMapper{
+					URI:       fh.URI(),
+					Content:   buf,
+					Converter: span.NewTokenConverter(fset, tok),
+				},
+				parseError: parseError,
+			}
 		}
 
 		// Fix any badly parsed parts of the AST.
@@ -319,6 +340,7 @@ func parseGo(ctx context.Context, fset *token.FileSet, fh source.FileHandle, mod
 	return &parseGoData{
 		src:        buf,
 		ast:        file,
+		tok:        tok,
 		mapper:     m,
 		parseError: parseError,
 		fixed:      fixed,
diff --git a/internal/lsp/regtest/diagnostics_test.go b/internal/lsp/regtest/diagnostics_test.go
index e7e66b3328..22d2a1c521 100644
--- a/internal/lsp/regtest/diagnostics_test.go
+++ b/internal/lsp/regtest/diagnostics_test.go
@@ -1098,3 +1098,23 @@ func main() {
 		)
 	})
 }
+
+// Reproduces golang/go#39763.
+func TestInvalidPackageName(t *testing.T) {
+	testenv.NeedsGo1Point(t, 15)
+
+	const pkgDefault = `
+-- go.mod --
+module mod.com
+-- main.go --
+package default
+
+func main() {}
+`
+	runner.Run(t, pkgDefault, func(t *testing.T, env *Env) {
+		env.OpenFile("main.go")
+		env.Await(
+			env.DiagnosticAtRegexp("main.go", "default"),
+		)
+	})
+}