match statements

compiler/lower/lower.odin

@@ -275,6 +275,18 @@ lower_compound_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instructi
 			target=ir.INVALID_REF, a=location, b=ir.INVALID_INSTRUCTION,
 			diagnostic=source.INVALID_DIAGNOSTIC,
 		})
+	case .Union_Tag:
+		// Read a tagged union's discriminant: the tag sits at offset 0, so the union's
+		// address is the tag's address — load the tag enum (`expr.type`) directly.
+		address := lower_location(state, expr.left)
+		if address == ir.INVALID_INSTRUCTION {
+			return append_recovery_value(state, expr.span, expr.type, expr.diagnostic)
+		}
+		return append_instruction(state, ir.Instruction{
+			op=.Union_Tag, span=expr.span, type=expr.type,
+			target=ir.INVALID_REF, a=address, b=ir.INVALID_INSTRUCTION,
+			diagnostic=source.INVALID_DIAGNOSTIC,
+		})
 	case .Slice:
 		// Array operands are addressed (locations) or spilled to a temporary
 		// (rvalues) by lower_location; other containers are slice/pointer values.
@@ -460,7 +472,7 @@ lower_expr :: proc(state: ^State, expr_id: hir.Expr_Id) -> ir.Instruction_Id {
 				})
 				_ = pop(&stack)
 			case .String, .Array, .Struct, .Range, .None, .Optional_Some, .Address, .Deref,
-			     .Index, .Slice, .Field, .Length, .Slice_Ptr, .Unwrap, .Orelse,
+			     .Index, .Slice, .Field, .Union_Tag, .Length, .Slice_Ptr, .Unwrap, .Orelse,
 			     .Not, .Eq, .Ne, .Lt, .Le, .Gt, .Ge, .And, .Or:
 				last = lower_compound_expr(state, frame.expr)
 				_ = pop(&stack)