Fix source-map emit panic for unclosed blocks

internal/printer/utilities.go

@@ -910,15 +910,23 @@ func newLineCharacterCache(source sourcemap.Source) *lineCharacterCache {
 // offset from the start of that line for the given byte position.
 func (c *lineCharacterCache) getLineAndCharacter(pos int) (line int, character core.UTF16Offset) {
 	line = scanner.ComputeLineOfPosition(c.lineMap, pos)
-	if c.hasCached && line == c.cachedLine && pos >= c.cachedPos {
+	lineStart := int(c.lineMap[line])
+	// When pos is beyond the source text (e.g., for error-recovery tokens like
+	// missing closing braces), we can't slice past the text end. Compute the
+	// UTF-16 length up to EOF and add the remaining byte offset arithmetically,
+	// matching TypeScript's computeLineAndCharacterOfPosition which uses
+	// arithmetic (position - lineStarts[lineNumber]) and handles this implicitly.
+	endPos := min(pos, len(c.text))
+	if c.hasCached && line == c.cachedLine && endPos >= c.cachedPos {
 		// Incremental: only count UTF-16 code units from the last cached position.
-		character = c.cachedChar + core.UTF16Len(c.text[c.cachedPos:pos])
+		character = c.cachedChar + core.UTF16Len(c.text[c.cachedPos:endPos])
 	} else {
 		// Full computation from line start.
-		character = core.UTF16Len(c.text[c.lineMap[line]:pos])
+		character = core.UTF16Len(c.text[lineStart:endPos])
 	}
+	character += core.UTF16Offset(pos - endPos)
 	c.cachedLine = line
-	c.cachedPos = pos
+	c.cachedPos = endPos
 	c.cachedChar = character
 	c.hasCached = true
 	return line, character

testdata/baselines/reference/compiler/sourceMapUnclosedBlock.errors.txt

@@ -0,0 +1,8 @@
+sourceMapUnclosedBlock.ts(1,2): error TS1005: '}' expected.
+
+
+==== sourceMapUnclosedBlock.ts (1 errors) ====
+    {
+
+!!! error TS1005: '}' expected.
+!!! related TS1007 sourceMapUnclosedBlock.ts:1:1: The parser expected to find a '}' to match the '{' token here.

testdata/baselines/reference/compiler/sourceMapUnclosedBlock.sourcemap.txt

@@ -0,0 +1,27 @@
+===================================================================
+JsFile: sourceMapUnclosedBlock.js
+mapUrl: sourceMapUnclosedBlock.js.map
+sourceRoot: 
+sources: sourceMapUnclosedBlock.ts
+===================================================================
+-------------------------------------------------------------------
+emittedFile:sourceMapUnclosedBlock.js
+sourceFile:sourceMapUnclosedBlock.ts
+-------------------------------------------------------------------
+>>>"use strict";
+>>>{ }
+1 >
+2 >^
+3 > ^
+4 >  ^
+5 >   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
+1 >
+2 >{
+3 > 
+4 >  
+1 >Emitted(2, 1) Source(1, 1) + SourceIndex(0)
+2 >Emitted(2, 2) Source(1, 2) + SourceIndex(0)
+3 >Emitted(2, 3) Source(1, 2) + SourceIndex(0)
+4 >Emitted(2, 4) Source(1, 3) + SourceIndex(0)
+---
+>>>//# sourceMappingURL=sourceMapUnclosedBlock.js.map

testdata/baselines/reference/compiler/sourceMapUnclosedBlock.symbols

@@ -0,0 +1,4 @@
+//// [tests/cases/compiler/sourceMapUnclosedBlock.ts] ////
+
+=== sourceMapUnclosedBlock.ts ===
+{

testdata/baselines/reference/compiler/sourceMapUnclosedBlock.types

@@ -0,0 +1,4 @@
+//// [tests/cases/compiler/sourceMapUnclosedBlock.ts] ////
+
+=== sourceMapUnclosedBlock.ts ===
+{

testdata/tests/cases/compiler/sourceMapUnclosedBlock.ts

@@ -0,0 +1,2 @@
+// @sourceMap: true
+{