support for-else and while-else

src/julia-parser.scm

@@ -1397,14 +1397,41 @@
             (if (eq? word 'quote)
                 (list 'quote blk)
                 blk))))
-       ((while)  (begin0 (list 'while (parse-cond s) (append (parse-block s) (list (line-number-node s))))
-                         (expect-end s word)))
+       ((while)
+        (let* ((con  (parse-cond s))
+               (body (parse-block s))
+               (nxt  (require-token s)))
+          (take-token s)
+          (case nxt
+            ((end)
+             `(while ,con
+                     ,(append body (list (line-number-node s)))))
+            ((else)
+             (let ((else-body (parse-block s)))
+               (expect-end s word)
+               `(while ,con
+                       ,body
+                       ,(append else-body (list (line-number-node s))))))
+            (else
+             (error (string "unexpected \"" nxt "\""))))))
        ((for)
         (let* ((ranges (parse-comma-separated-iters s))
-               (body   (parse-block s)))
-          (expect-end s word)
-          `(for ,(if (length= ranges 1) (car ranges) (cons 'block ranges))
-                ,(append body (list (line-number-node s))))))
+               (ranges (if (length= ranges 1) (car ranges) (cons 'block ranges)))
+               (body   (parse-block s))
+               (nxt    (require-token s)))
+          (take-token s)
+          (case nxt
+            ((end)
+             `(for ,ranges
+                   ,(append body (list (line-number-node s)))))
+            ((else)
+             (let ((else-body (parse-block s)))
+               (expect-end s word)
+               `(for ,ranges
+                     ,body
+                     ,(append else-body (list (line-number-node s))))))
+            (else
+             (error (string "unexpected \"" nxt "\""))))))
 
        ((let)
         (let ((binds (if (memv (peek-token s) '(#\newline #\;))

src/julia-syntax.scm

@@ -1823,7 +1823,9 @@
                             (if ,g ,g
                                 ,(loop (cdr tail)))))))))))
 
-(define (expand-for lhss itrs body)
+(define (expand-for lhss itrs body . else-body)
+  (if (and (length> lhss 1) (not (null? else-body)))
+      (error "multi-dimensional for-loops are not allowed to have else-blocks"))
   (define (outer? x) (and (pair? x) (eq? (car x) 'outer)))
   (let ((copied-vars  ;; variables not declared `outer` are copied in the innermost loop
          ;; TODO: maybe filter these to remove vars not assigned in the loop
@@ -1867,7 +1869,8 @@
                            (_do_while
                             (block ,body
                                    (= ,next (call (top iterate) ,coll ,state)))
-                            (call (top not_int) (call (core ===) ,next (null))))))))))))
+                            (call (top not_int) (call (core ===) ,next (null))))
+                           ,@else-body))))))))
 
 ;; wrap `expr` in a function appropriate for consuming values from given ranges
 (define (func-for-generator-ranges expr range-exprs flat outervars)
@@ -2134,10 +2137,17 @@
   (list* (car e) (expand-condition (cadr e)) (map expand-forms (cddr e))))
 
 (define (expand-while e)
-  `(break-block loop-exit
-                (_while ,(expand-condition (cadr e))
-                        (break-block loop-cont
-                                     (scope-block ,(blockify (expand-forms (caddr e))))))))
+  (if (length= e 3)
+      `(break-block loop-exit
+                    (_while ,(expand-condition (cadr e))
+                            (break-block loop-cont
+                                         (scope-block ,(blockify (expand-forms (caddr e)))))))
+      `(break-block loop-exit
+                    (if ,(expand-condition (cadr e))
+                        (_do_while (break-block loop-cont
+                                                (scope-block ,(blockify (expand-forms (caddr e)))))
+                                   ,(expand-condition (cadr e)))
+                        (scope-block ,(blockify (expand-forms (cadddr e))))))))
 
 (define (expand-vcat e
                      (vcat '((top vcat)))
@@ -2798,7 +2808,7 @@
      (let ((ranges (if (eq? (car (cadr e)) 'block)
                        (cdr (cadr e))
                        (list (cadr e)))))
-       (expand-forms (expand-for (map cadr ranges) (map caddr ranges) (caddr e)))))
+       (expand-forms (apply expand-for (map cadr ranges) (map caddr ranges) (cddr e)))))
 
    '&&     (lambda (e) (expand-forms (expand-and e)))
    '|\|\|| (lambda (e) (expand-forms (expand-or  e)))

test/syntax.jl

@@ -537,18 +537,19 @@ end
 # make sure that incomplete tags are detected correctly
 # (i.e. error messages in src/julia-parser.scm must be matched correctly
 # by the code in base/client.jl)
-for (str, tag) in Dict("" => :none, "\"" => :string, "#=" => :comment, "'" => :char,
-                       "`" => :cmd, "begin;" => :block, "quote;" => :block,
-                       "let;" => :block, "for i=1;" => :block, "function f();" => :block,
-                       "f() do x;" => :block, "module X;" => :block, "mutable struct X;" => :block,
-                       "struct X;" => :block, "(" => :other, "[" => :other,
-                       "for" => :other, "function" => :other,
-                       "f() do" => :other, "module" => :other, "mutable struct" => :other,
-                       "struct" => :other,
-                       "quote" => using_JuliaSyntax ? :block : :other,
-                       "let" => using_JuliaSyntax ? :block : :other,
-                       "begin" => using_JuliaSyntax ? :block : :other,
-                      )
+@testset "incomplete tags: $str => $tag" for (str, tag) in Dict(
+        "" => :none, "\"" => :string, "#=" => :comment, "'" => :char,
+        "`" => :cmd, "begin;" => :block, "quote;" => :block,
+        "let;" => :block, "for i=1;" => :other, "function f();" => :block,
+        "f() do x;" => :block, "module X;" => :block, "mutable struct X;" => :block,
+        "struct X;" => :block, "(" => :other, "[" => :other,
+        "for" => :other, "function" => :other,
+        "f() do" => :other, "module" => :other, "mutable struct" => :other,
+        "struct" => :other,
+        "quote" => using_JuliaSyntax ? :block : :other,
+        "let" => using_JuliaSyntax ? :block : :other,
+        "begin" => using_JuliaSyntax ? :block : :other,
+    )
     @test Base.incomplete_tag(Meta.parse(str, raise=false)) == tag
 end
 
@@ -2429,7 +2430,7 @@ end
 @test x == 6
 
 # issue #36196
-@test_parseerror "(for i=1; println())"  "\"for\" at none:1 expected \"end\", got \")\""
+@test_parseerror "(for i=1; println())"  "unexpected \")\""
 @test_parseerror "(try i=1; println())"  "\"try\" at none:1 expected \"end\", got \")\""
 
 # issue #36272
@@ -3987,3 +3988,51 @@ end
 @test f45494() === (0,)
 
 @test_throws "\"esc(...)\" used outside of macro expansion" eval(esc(:(const x=1)))
+
+@testset "for else" begin
+    a = Int[]
+    for i in 1:0
+        push!(a, 1)
+    else
+        push!(a, 2)
+    end
+    @test a == [2]
+
+    a = Int[]
+    for i in 1:3
+        push!(a, 1)
+    else
+        push!(a, 2)
+    end
+    @test a == [1, 1, 1]
+
+    @test_throws "multi-dimensional for-loops are not allowed to have else-blocks" eval(:(
+        for i in 1:0, j in 1:3
+            print(1)
+        else
+            print(2)
+        end
+    ))
+end
+
+@testset "while else" begin
+    a = Int[]
+    i = 1
+    while i ≤ 0
+        push!(a, 1)
+        i += 1
+    else
+        push!(a, 2)
+    end
+    @test a == [2]
+
+    a = Int[]
+    i = 1
+    while i ≤ 3
+        push!(a, 1)
+        i += 1
+    else
+        push!(a, 2)
+    end
+    @test a == [1, 1, 1]
+end