Merge pull request #15807 from JuliaLang/jb/generator_destructuring

fix a bug in lowering generator expressions with `(a,b) in itr`

Author: JeffBezanson

src/julia-syntax.scm

@@ -1963,9 +1963,9 @@
        (let* ((argname (if (and (length= vars 1) (symbol? (car vars)))
                            (car vars)
                            (gensy)))
-              (splat (if (eq? argname (car vars))
-                         '()
-                         `((= (tuple ,@vars) ,argname)))))
+              (splat (cond ((eq? argname (car vars))  '())
+                           ((length= vars 1)          `((= ,(car vars) ,argname)))
+                           (else                      `((= (tuple ,@vars) ,argname))))))
          (expand-forms
           `(call (top Generator) (-> ,argname (block ,@splat ,expr))
                  ,(if (length= ranges 1)

test/functional.jl

@@ -239,3 +239,9 @@ end
 @test_throws DimensionMismatch Base.IteratorND(1:2, (2,3))
 
 @test collect(Base.Generator(+, [1,2], [10,20])) == [11,22]
+
+# generator with destructuring
+let d = Dict(:a=>1, :b=>2), a = Dict(3=>4, 5=>6)
+    @test Dict( v=>(k,) for (k,v) in d) == Dict(2=>(:b,), 1=>(:a,))
+    @test Dict( (x,b)=>(c,y) for (x,c) in d, (b,y) in a ) == Dict((:a,5)=>(1,6),(:b,5)=>(2,6),(:a,3)=>(1,4),(:b,3)=>(2,4))
+end