fix #17701, better error message for i == 3 && i+=1

Author: JeffBezanson

src/ast.scm

@@ -60,7 +60,7 @@
                              "")))
                 ((comparison) (apply string (map deparse (cdr e))))
                 ((in) (string (deparse (cadr e)) " in " (deparse (caddr e))))
-                ((ssavalue) (string "SSAValue(" (cdr e) ")"))
+                ((ssavalue) (string "SSAValue(" (cadr e) ")"))
                 ((line) (if (length= e 2)
                             (string "# line " (cadr e))
                             (string "# " (caddr e) ", line " (cadr e))))

src/julia-syntax.scm

@@ -1469,6 +1469,9 @@
            `(block ,@(cdr e)
                    ,(expand-update-operator op op= (car e) rhs T))))
         (else
+         (if (and (pair? lhs)
+                  (not (memq (car lhs) '(|.| tuple vcat typed_hcat typed_vcat))))
+             (error (string "invalid assignment location \"" (deparse lhs) "\"")))
          (expand-update-operator- op op= lhs rhs declT))))
 
 (define (lower-update-op e)

test/parse.jl

@@ -648,3 +648,5 @@ for op in ["+", "-", "\$", "|", ".+", ".-", "*", ".*"]
     @test_throws ParseError parse("$op in [+, -]")
 end
 
+# issue #17701
+@test expand(:(i==3 && i+=1)) == Expr(:error, "invalid assignment location \"==(i,3)&&i\"")