better parser errors

error_test/parser/expression_errors.sui

@@ -0,0 +1,43 @@
+# Expression and statement errors
+
+# Missing variable name in let
+fn test() -> int
+    let = 5
+    42
+
+# Missing equals in assignment
+fn test() -> int
+    let x 5
+    x
+
+# Missing expression after operator
+fn test() -> int
+    5 +
+
+# Invalid array syntax (missing comma)
+fn test() -> int
+    let arr = [1 2 3]
+    arr[0]
+
+# Missing closing bracket in array
+fn test() -> int
+    let arr = [1, 2, 3
+    arr[0]
+
+# Invalid struct literal (missing field value)
+fn test() -> int
+    struct Point
+        x: int
+        y: int
+    end
+    let p = Point { x: 5, y }
+    p.x
+
+# Missing colon in struct literal
+fn test() -> int
+    struct Point
+        x: int
+        y: int
+    end
+    let p = Point { x 5, y: 10 }
+    p.x