From e6c324c2e70288ca0df86efd0957ef2c5b66f39c Mon Sep 17 00:00:00 2001
From: dos-reis <gdr@axiomatics.org>
Date: Sun, 13 Jun 2010 01:33:35 +0000
Subject: 	* interp/compiler.boot (complainIfShadowing): New. 
 (compStepIterator): Use it to warn about loop variable shadowing 
 declaration in enclosing scope. 	(compIterator): Likewise.

---
 src/ChangeLog            |  7 +++++++
 src/interp/compiler.boot | 11 ++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/ChangeLog b/src/ChangeLog
index 99d8b460..e9dd5d4b 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2010-06-12  Gabriel Dos Reis  <gdr@cs.tamu.edu>
+
+	* interp/compiler.boot (complainIfShadowing): New.
+	(compStepIterator): Use it to warn about loop variable shadowing
+	declaration in enclosing scope.
+	(compIterator): Likewise.
+
 2010-06-12  Gabriel Dos Reis  <gdr@cs.tamu.edu>
 
 	* algebra/kl.spad.pamphlet (Kernel): Don't clear the on
diff --git a/src/interp/compiler.boot b/src/interp/compiler.boot
index 87d07c89..ceae230f 100644
--- a/src/interp/compiler.boot
+++ b/src/interp/compiler.boot
@@ -2362,12 +2362,19 @@ compIntegerValue(x,e) ==
   comp(x,$PositiveInteger,e) or
     comp(x,$NonNegativeInteger,e) or
       compOrCroak(x,$Integer,e)
-  
+
+++ Issue a diagnostic if `x' names a loop variable with a matching
+++ declaration  or definition in the enclosing scope.  
+complainIfShadowing(x,e) ==
+  if getmode(x,e) ~= nil then
+    stackWarning('"loop variable %1b shadows variable from enclosing scope",[x])
+
 ++ Attempt to compile a `for' iterator of the form
 ++     for index in start..final by inc
 ++ where the bound `final' may be missing.
 compStepIterator(index,start,final,inc,e) ==
   checkVariableName index
+  complainIfShadowing(index,e)
   $formalArgList := [index,:$formalArgList]
   [start,startMode,e] := compIntegerValue(start,e) or return
     stackMessage('"start value of index: %1b must be an integer",[start])
@@ -2389,6 +2396,7 @@ compIterator(it,e) ==
     -- ??? Allow for declared iterator variable.
   it is ["IN",x,y] =>
     checkVariableName x
+    complainIfShadowing(x,e)
     --these two lines must be in this order, to get "for f in list f"
     --to give  an error message if f is undefined
     [y',m,e]:= comp(y,$EmptyMode,e) or return nil
@@ -2403,6 +2411,7 @@ compIterator(it,e) ==
     [["IN",x,y''],e]
   it is ["ON",x,y] =>
     checkVariableName x
+    complainIfShadowing(x,e)
     $formalArgList:= [x,:$formalArgList]
     [y',m,e]:= comp(y,$EmptyMode,e) or return nil
     [mOver,mUnder]:=
-- 
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