fix(65078): keep empty spans for missing nodes when skipping trivia

tsc/internal/diagnosticwriter/diagnosticwriter.go

@@ -270,6 +270,11 @@ func FormatDiagnosticWithColorAndContext(output io.Writer, diagnostic Diagnostic
 }
 
 func writeCodeSnippet(writer io.Writer, sourceFile FileLike, start int, length int, squiggleColor string, indent string, formatOpts *FormattingOptions) {
+	// Inverted diagnostic spans (end < start) must not reach strings.Repeat with a
+	// negative count. Treat them as empty markers at `start` (see #65078).
+	if length < 0 {
+		length = 0
+	}
 	firstLine, firstLineChar := scanner.GetECMALineAndUTF16CharacterOfPosition(sourceFile, start)
 	lastLine, lastLineChar := scanner.GetECMALineAndUTF16CharacterOfPosition(sourceFile, start+length)
 	if length == 0 {

tsc/internal/parser/parser.go

@@ -6472,7 +6472,19 @@ func (p *Parser) inAwaitContext() bool {
 }
 
 func (p *Parser) skipRangeTrivia(textRange core.TextRange) core.TextRange {
-	return core.NewTextRange(scanner.SkipTrivia(p.sourceText, textRange.Pos()), textRange.End())
+	// Missing nodes use an empty range (pos == end). Skipping trivia from that
+	// position can move start past end and invert the span, which then panics
+	// in --pretty (strings.Repeat with a negative count). Match Strada's
+	// getErrorSpanForNode: do not skip trivia for missing locations.
+	// See https://github.com/microsoft/TypeScript/issues/65078
+	if textRange.Pos() == textRange.End() {
+		return textRange
+	}
+	start := scanner.SkipTrivia(p.sourceText, textRange.Pos())
+	if start > textRange.End() {
+		return textRange
+	}
+	return core.NewTextRange(start, textRange.End())
 }
 
 func isReservedWord(token ast.Kind) bool {
@@ -6742,7 +6754,7 @@ func (p *Parser) parseResolutionMode(mode string, pos int, end int) (resolutionK
 }
 
 func (p *Parser) jsErrorAtRange(loc core.TextRange, message *diagnostics.Message, args ...any) {
-	p.jsDiagnostics = append(p.jsDiagnostics, ast.NewDiagnostic(nil, core.NewTextRange(scanner.SkipTrivia(p.sourceText, loc.Pos()), loc.End()), message, args...))
+	p.jsDiagnostics = append(p.jsDiagnostics, ast.NewDiagnostic(nil, p.skipRangeTrivia(loc), message, args...))
 }
 
 func (p *Parser) checkJSDecoratorSyntax(node *ast.Node) {
@@ -6782,12 +6794,12 @@ func (p *Parser) checkJSDecoratorSyntax(node *ast.Node) {
 						if trailingDecoratorIndex >= 0 {
 							diag := ast.NewDiagnostic(
 								nil,
-								core.NewTextRange(scanner.SkipTrivia(p.sourceText, modifiers[trailingDecoratorIndex].Loc.Pos()), modifiers[trailingDecoratorIndex].Loc.End()),
+								p.skipRangeTrivia(modifiers[trailingDecoratorIndex].Loc),
 								diagnostics.Decorators_may_not_appear_after_export_or_export_default_if_they_also_appear_before_export,
 							)
 							diag.AddRelatedInfo(ast.NewDiagnostic(
 								nil,
-								core.NewTextRange(scanner.SkipTrivia(p.sourceText, modifiers[decoratorIndex].Loc.Pos()), modifiers[decoratorIndex].Loc.End()),
+								p.skipRangeTrivia(modifiers[decoratorIndex].Loc),
 								diagnostics.Decorator_used_before_export_here,
 							))
 							p.jsDiagnostics = append(p.jsDiagnostics, diag)

tsc/internal/parser/parser_test.go

@@ -571,3 +571,29 @@ namespace N {
 	assert.Equal(t, positionMap.UTF8ToUTF16(afterBoxDrawingCharacter), afterBoxDrawingCharacter-2)
 	assert.Equal(t, positionMap.UTF8ToUTF16(len(sourceText)), len(sourceText)-2)
 }
+
+// https://github.com/microsoft/TypeScript/issues/65078
+// An empty (missing) type annotation in a JS file must keep an empty diagnostic
+// span at the missing location. Skipping trivia used to invert the span
+// (start past end), which crashed --pretty and reported the wrong column.
+func TestJSErrorAtMissingTypeAnnotationKeepsEmptySpan(t *testing.T) {
+	t.Parallel()
+	sourceText := "var R: ;"
+	opts := ast.SourceFileParseOptions{
+		FileName: "/a.js",
+		PathKey:  "/a.js",
+	}
+	file := parser.ParseSourceFile(opts, sourceText, core.ScriptKindJS)
+
+	var found *ast.Diagnostic
+	for _, d := range file.JSDiagnostics() {
+		if d.Code() == diagnostics.Type_annotations_can_only_be_used_in_TypeScript_files.Code() {
+			found = d
+			break
+		}
+	}
+	assert.Assert(t, found != nil, "expected TS8010")
+	// "var R:" ends at index 6; the missing type occupies [6,6].
+	assert.Equal(t, found.Pos(), 6)
+	assert.Equal(t, found.Len(), 0)
+}