Enhance diagnostics for computed property expressions: improve error messages and hints for unclosed computed property expressions and invalid computed property syntax, and add comprehensive test cases for better clarity and coverage.

pkg/compiler/internal/diagnostics/match_error_literals.go

@@ -68,11 +68,19 @@ func matchLiteralErrors(src *file.Source, err *CompilationError, offending *Toke
 				span.End++
 			}
 
+			if !isKeyword(offending.PrevAt(2)) {
+				err.Message = "Unclosed computed property expression"
+				err.Hint = "Add a closing ']' to complete the computed property expression."
+				err.Spans = []ErrorSpan{
+					NewMainErrorSpan(span, "missing ']'"),
+				}
+			} else {
 				err.Message = "Unclosed array literal"
 				err.Hint = "Add a closing ']' to complete the array."
 				err.Spans = []ErrorSpan{
 					NewMainErrorSpan(span, "missing ']'"),
 				}
+			}
 
 			return true
 		}
@@ -182,6 +190,20 @@ func matchLiteralErrors(src *file.Source, err *CompilationError, offending *Toke
 
 			return true
 		}
+
+		if is(offending, "[") && token == "]" {
+			span := spanFromTokenSafe(offending.Token(), src)
+			span.End++
+
+			val := offending.Prev().String()
+			err.Message = "Expected expression inside computed property brackets"
+			err.Hint = fmt.Sprintf("Provide a property key or index inside '[ ]', e.g. %s[0] or %s[\"key\"].", val, val)
+			err.Spans = []ErrorSpan{
+				NewMainErrorSpan(span, "missing expression"),
+			}
+
+			return true
+		}
 	}
 
 	return false

test/integration/compiler/compiler_errors_syntax_literals_test.go

@@ -306,8 +306,19 @@ func TestLiteralsSyntaxErrors(t *testing.T) {
 			RETURN v
 		`, E{
 				Kind:    compiler.SyntaxError,
-				Message: "Expected end value before '..' in range expression",
-				Hint:    "Object properties must have a name before the colon, e.g. { property: 123 }.",
-			}, "Incomplete array access"),
+				Message: "Unclosed computed property expression",
+				Hint:    "Add a closing ']' to complete the computed property expression.",
+			}, "Unclosed computed property expression"),
+
+		ErrorCase(
+			`
+			LET arr = [1, 2, 3]
+			LET v = arr[]
+			RETURN v
+		`, E{
+				Kind:    compiler.SyntaxError,
+				Message: "Expected expression inside computed property brackets",
+				Hint:    "Provide a property key or index inside '[ ]', e.g. arr[0] or arr[\"key\"].",
+			}, "Invalid computed property expression"),
 	})
 }