Hoist for loop control var to enclosing scope (#4376)

* Hoist `for` loop control var to enclosing scope

It should be possible to reference the last value assigned to a `for`
loop control var when the loop terminates. This makes it easier to detect
if we broke out of the loop among other things.  This change makes fish
`for` loops behave like most other shells.

Fixes #1935

* Remove redundant line

tests/argparse.err

@@ -32,9 +32,9 @@ argparse: Implicit int short flag '#' does not allow modifiers like '='
 ####################
 # Invalid arg in the face of a "#-val" spec
 argparse: Unknown option '-x'
-Standard input (line 38): 
-argparse '#-val' -- abc -x def
-^
+Standard input (line 41): 
+    argparse '#-val' -- abc -x def
+    ^
 
 ####################
 # Defining a short flag more than once

tests/argparse.in

@@ -32,28 +32,42 @@ begin
 end
 
 logmsg Invalid \"#-val\" spec
-argparse '#-val=' -- abc -x def
+begin
+    argparse '#-val=' -- abc -x def
+end
 
 logmsg Invalid arg in the face of a \"#-val\" spec
-argparse '#-val' -- abc -x def
+begin
+    argparse '#-val' -- abc -x def
+end
 
 logmsg Defining a short flag more than once
-argparse 's/short' 'x/xray' 's/long' -- -s -x --long
+begin
+    argparse 's/short' 'x/xray' 's/long' -- -s -x --long
+end
 
 logmsg Defining a long flag more than once
-argparse 's/short' 'x/xray' 'l/short' -- -s -x --long
+begin
+    argparse 's/short' 'x/xray' 'l/short' -- -s -x --long
+end
 
 logmsg Defining an implicit int flag more than once
-argparse '#-val' 'x/xray' 'v#val' -- -s -x --long
+begin
+    argparse '#-val' 'x/xray' 'v#val' -- -s -x --long
+end
 
 logmsg Defining an implicit int flag with modifiers
-argparse 'v#val=' --
+begin
+    argparse 'v#val=' --
+end
 
 ##########
 # Now verify that validly formed invocations work as expected.
 
 logmsg No args
-argparse h/help --
+begin
+    argparse h/help --
+end
 
 logmsg One arg and no matching flags
 begin
@@ -80,47 +94,56 @@ begin
 end
 
 logmsg Implicit int flags work
-for v in (set -l -n); set -e $v; end
-argparse '#-val' -- abc -123 def
-set -l
-for v in (set -l -n); set -e $v; end
-argparse 'v/verbose' '#-val' 't/token=' -- -123 a1 --token woohoo --234 -v a2 --verbose
-set -l
+begin
+    argparse '#-val' -- abc -123 def
+    set -l
+end
+begin
+    argparse 'v/verbose' '#-val' 't/token=' -- -123 a1 --token woohoo --234 -v a2 --verbose
+    set -l
+end
 
 logmsg Should be set to 987
-for v in (set -l -n); set -e $v; end
-argparse 'm#max' -- argle -987 bargle
-set -l
+begin
+    argparse 'm#max' -- argle -987 bargle
+    set -l
+end
 
 logmsg Should be set to 765
-for v in (set -l -n); set -e $v; end
-argparse 'm#max' -- argle -987 bargle --max 765
-set -l
+begin
+    argparse 'm#max' -- argle -987 bargle --max 765
+    set -l
+end
 
 logmsg Bool short flag only
-for v in (set -l -n); set -e $v; end
-argparse 'C' 'v' -- -C -v arg1 -v arg2
-set -l
+begin
+    argparse 'C' 'v' -- -C -v arg1 -v arg2
+    set -l
+end
 
 logmsg Value taking short flag only
-for v in (set -l -n); set -e $v; end
-argparse 'x=' 'v/verbose' -- --verbose arg1 -v -x arg2
-set -l
+begin
+    argparse 'x=' 'v/verbose' -- --verbose arg1 -v -x arg2
+    set -l
+end
 
 logmsg Implicit int short flag only
-for v in (set -l -n); set -e $v; end
-argparse 'x#' 'v/verbose' -- -v -v argle -v -x 321 bargle
-set -l
+begin
+    argparse 'x#' 'v/verbose' -- -v -v argle -v -x 321 bargle
+    set -l
+end
 
 logmsg Implicit int short flag only with custom validation passes
-for v in (set -l -n); set -e $v; end
-argparse 'x#!_validate_int --max 500' 'v/verbose' -- -v -v -x 499 -v
-set -l
+begin
+    argparse 'x#!_validate_int --max 500' 'v/verbose' -- -v -v -x 499 -v
+    set -l
+end
 
 logmsg Implicit int short flag only with custom validation fails
-for v in (set -l -n); set -e $v; end
-argparse 'x#!_validate_int --min 500' 'v/verbose' -- -v -v -x 499 -v
-set -l
+begin
+    argparse 'x#!_validate_int --min 500' 'v/verbose' -- -v -v -x 499 -v
+    set -l
+end
 
 ##########
 # Verify that flag value validation works.

tests/test1.err

@@ -38,6 +38,9 @@ fish: You cannot use read-only variable 'status' in a for loop
 for status in a b c
     ^
 
+####################
+# For loop control vars available outside the for block
+
 ####################
 # Comments allowed in between lines (#1987)
 

tests/test1.in

@@ -155,6 +155,35 @@ for status in a b c
   echo $status
 end
 
+logmsg For loop control vars available outside the for block
+begin
+  set -l loop_var initial-value
+  for loop_var in a b c
+    # do nothing
+  end
+  set --show loop_var
+end
+
+set -g loop_var global_val
+function loop_test
+  for loop_var in a b c
+    if test $loop_var = b
+      break
+    end
+  end
+  set --show loop_var
+end
+loop_test
+set --show loop_var
+
+begin
+  set -l loop_var
+  for loop_var in aa bb cc
+  end
+  set --show loop_var
+end
+set --show loop_var
+
 logmsg 'Comments allowed in between lines (#1987)'
 echo before comment \
   # comment

tests/test1.out

@@ -90,6 +90,36 @@ Checking for infinite loops in no-execute
 ####################
 # For loops with read-only vars is an error (#4342)
 
+####################
+# For loop control vars available outside the for block
+$loop_var: set in local scope, unexported, with 1 elements
+$loop_var[1]: length=1 value=|c|
+$loop_var: not set in global scope
+$loop_var: not set in universal scope
+
+$loop_var: set in local scope, unexported, with 1 elements
+$loop_var[1]: length=1 value=|b|
+$loop_var: set in global scope, unexported, with 1 elements
+$loop_var[1]: length=10 value=|global_val|
+$loop_var: not set in universal scope
+
+$loop_var: not set in local scope
+$loop_var: set in global scope, unexported, with 1 elements
+$loop_var[1]: length=10 value=|global_val|
+$loop_var: not set in universal scope
+
+$loop_var: set in local scope, unexported, with 1 elements
+$loop_var[1]: length=2 value=|cc|
+$loop_var: set in global scope, unexported, with 1 elements
+$loop_var[1]: length=10 value=|global_val|
+$loop_var: not set in universal scope
+
+$loop_var: not set in local scope
+$loop_var: set in global scope, unexported, with 1 elements
+$loop_var[1]: length=10 value=|global_val|
+$loop_var: not set in universal scope
+
+
 ####################
 # Comments allowed in between lines (#1987)
 before comment after comment