support for for-else and while-else

companion to JuliaLang/julia#56153

Author: simeonschaub

src/expr.jl

@@ -138,7 +138,7 @@ function _string_to_Expr(args)
         #   """\n  a\n  b""" ==>  "a\nb"
         return only(args2)
     else
-        # This only happens when the kind is K"string" or when an error has occurred. 
+        # This only happens when the kind is K"string" or when an error has occurred.
         return Expr(:string, args2...)
     end
 end
@@ -157,7 +157,7 @@ function _fixup_Expr_children!(head, loc, args)
         arg = args[i]
         was_parens = @isexpr(arg, :parens)
         arg = _strip_parens(arg)
-        if @isexpr(arg, :(=)) && eq_to_kw_in_call && i > 1 
+        if @isexpr(arg, :(=)) && eq_to_kw_in_call && i > 1
             arg = Expr(:kw, arg.args...)
         elseif k != K"parens" && @isexpr(arg, :., 1) && arg.args[1] isa Tuple
             h, a = arg.args[1]::Tuple{SyntaxHead,Any}
@@ -310,10 +310,10 @@ function _internal_node_to_Expr(source, srcrange, head, childranges, childheads,
         args[1] = length(iters) == 1 ? only(iters) : Expr(:block, iters...)
         # Add extra line number node for the `end` of the block. This may seem
         # useless but it affects code coverage.
-        push!(args[2].args, endloc)
+        push!(args[end].args, endloc)
     elseif k == K"while"
         # Line number node for the `end` of the block as in `for` loops.
-        push!(args[2].args, endloc)
+        push!(args[end].args, endloc)
     elseif k in KSet"tuple vect braces"
         # Move parameters blocks to args[1]
         _reorder_parameters!(args, 1)

src/parser.jl

@@ -1813,6 +1813,13 @@ function parse_resword(ps::ParseState)
         bump(ps, TRIVIA_FLAG)
         parse_cond(ps)
         parse_block(ps)
+        bump_trivia(ps)
+        if peek(ps) == K"else"
+            else_mark = position(ps)
+            bump(ps, TRIVIA_FLAG)
+            parse_block(ps)
+            min_supported_version(v"1.12", ps, else_mark, "`else` after `for`")
+        end
         bump_closing_token(ps, K"end")
         emit(ps, mark, K"while")
     elseif word == K"for"
@@ -1821,6 +1828,13 @@ function parse_resword(ps::ParseState)
         bump(ps, TRIVIA_FLAG)
         parse_iteration_specs(ps)
         parse_block(ps)
+        bump_trivia(ps)
+        if peek(ps) == K"else"
+            else_mark = position(ps)
+            bump(ps, TRIVIA_FLAG)
+            parse_block(ps)
+            min_supported_version(v"1.12", ps, else_mark, "`else` after `for`")
+        end
         bump_closing_token(ps, K"end")
         emit(ps, mark, K"for")
     elseif word == K"let"

test/expr.jl

@@ -189,6 +189,21 @@
                           LineNumberNode(3)
                      )
                 )
+            if VERSION >= v"1.12-"
+                @test parsestmt("for x=xs\ny\nelse\nz\nend") ==
+                    Expr(:for,
+                         Expr(:(=), :x, :xs),
+                         Expr(:block,
+                              LineNumberNode(2),
+                              :y,
+                         ),
+                         Expr(:block,
+                              LineNumberNode(4),
+                              :z,
+                              LineNumberNode(5)
+                         )
+                    )
+            end
             @test parsestmt("while cond\n\nend") ==
                 Expr(:while,
                      :cond,
@@ -206,6 +221,21 @@
                           LineNumberNode(3)
                      )
                 )
+            if VERSION >= v"1.12-"
+                @test parsestmt("while cond\ny\nelse\nz\nend") ==
+                    Expr(:while,
+                         :cond,
+                         Expr(:block,
+                              LineNumberNode(2),
+                              :y,
+                         ),
+                         Expr(:block,
+                              LineNumberNode(4),
+                              :z,
+                              LineNumberNode(5)
+                         )
+                    )
+            end
         end
     end
 
@@ -361,7 +391,7 @@
             Expr(:call, :f, Expr(:parameters, Expr(:kw, :b, 2)))
         @test parsestmt("f(a=1; b=2)") ==
             Expr(:call, :f, Expr(:parameters, Expr(:kw, :b, 2)), Expr(:kw, :a, 1))
-        @test parsestmt("f(a; b; c)") == 
+        @test parsestmt("f(a; b; c)") ==
             Expr(:call, :f, Expr(:parameters, Expr(:parameters, :c), :b), :a)
         @test parsestmt("+(a=1,)") ==
             Expr(:call, :+, Expr(:kw, :a, 1))
@@ -371,11 +401,11 @@
         # Operator calls:  = is not :kw
         @test parsestmt("(x=1) != 2") ==
             Expr(:call, :!=, Expr(:(=), :x, 1), 2)
-        @test parsestmt("+(a=1)") == 
+        @test parsestmt("+(a=1)") ==
             Expr(:call, :+, Expr(:(=), :a, 1))
-        @test parsestmt("(a=1)'") == 
+        @test parsestmt("(a=1)'") ==
             Expr(Symbol("'"), Expr(:(=), :a, 1))
-        @test parsestmt("(a=1)'ᵀ") == 
+        @test parsestmt("(a=1)'ᵀ") ==
             Expr(:call, Symbol("'ᵀ"), Expr(:(=), :a, 1))
 
         # Dotcall
@@ -583,8 +613,8 @@
             Expr(:generator, :x,
                  Expr(:filter, :z, Expr(:(=), :a, :as), Expr(:(=), :b, :bs)))
         @test parsestmt("(x for a in as, b in bs for c in cs, d in ds)") ==
-            Expr(:flatten, 
-                Expr(:generator, 
+            Expr(:flatten,
+                Expr(:generator,
                      Expr(:generator, :x, Expr(:(=), :c, :cs), Expr(:(=), :d, :ds)),
                      Expr(:(=), :a, :as), Expr(:(=), :b, :bs)))
         @test parsestmt("(x for a in as for b in bs if z)") ==
@@ -754,7 +784,7 @@
         @test parsestmt("global x ~ 1") == Expr(:global, Expr(:call, :~, :x, 1))
         @test parsestmt("global x += 1") == Expr(:global, Expr(:+=, :x, 1))
 
-        # Parsing of global/local with 
+        # Parsing of global/local with
         @test parsestmt("global (x,y)") == Expr(:global, :x, :y)
         @test parsestmt("local (x,y)") == Expr(:local, :x, :y)
     end

test/parser.jl

@@ -474,9 +474,13 @@ tests = [
         # while
         "while cond body end"  =>  "(while cond (block body))"
         "while x < y \n a \n b \n end"  =>  "(while (call-i x < y) (block a b))"
+        ((v=v"1.12",), "while x < y \n a \n else \n b \n end") =>
+            "(while (call-i x < y) (block a) (block b))"
         # for
         "for x in xs end" => "(for (iteration (in x xs)) (block))"
         "for x in xs, y in ys \n a \n end" => "(for (iteration (in x xs) (in y ys)) (block a))"
+        ((v=v"1.12",), "for x in xs \n a \n else \n b \n end") =>
+            "(for (iteration (in x xs)) (block a) (block b))"
         # let
         "let x=1\n end"    =>  "(let (block (= x 1)) (block))"
         "let x=1 ; end"    =>  "(let (block (= x 1)) (block))"