minor breaking change: for loop bodies now get their own scope

changelog.md

@@ -41,6 +41,14 @@
   what to return if the environment variable does not exist.
 - Removed PDCurses wrapper from the stdlib and published it as a separate
   Nimble package.
+- Bodies of ``for`` loops now get their own scope:
+
+.. code-block:: nim
+  # now compiles:
+  for i in 0..4:
+    let i = i + 1
+    echo i
+
 - The parsing rules of ``if`` expressions were changed so that multiple
   statements are allowed in the branches. We found few code examples that
   now fail because of this change, but here is one:

compiler/semgnrc.nim

@@ -335,8 +335,10 @@ proc semGenericStmt(c: PContext, n: PNode,
     n.sons[L - 2] = semGenericStmt(c, n.sons[L-2], flags, ctx)
     for i in countup(0, L - 3):
       addTempDecl(c, n.sons[i], skForVar)
+    openScope(c)
     n.sons[L - 1] = semGenericStmt(c, n.sons[L-1], flags, ctx)
     closeScope(c)
+    closeScope(c)
   of nkBlockStmt, nkBlockExpr, nkBlockType:
     checkSonsLen(n, 2)
     openScope(c)

compiler/semstmts.nim

@@ -697,7 +697,9 @@ proc semForVars(c: PContext, n: PNode): PNode =
       if sfGenSym notin v.flags and not isDiscardUnderscore(v):
         addForVarDecl(c, v)
   inc(c.p.nestedLoopCounter)
+  openScope(c)
   n.sons[length-1] = semStmt(c, n.sons[length-1])
+  closeScope(c)
   dec(c.p.nestedLoopCounter)
 
 proc implicitIterator(c: PContext, it: string, arg: PNode): PNode =

compiler/semtempl.nim

@@ -366,8 +366,10 @@ proc semTemplBody(c: var TemplCtx, n: PNode): PNode =
     n.sons[L-2] = semTemplBody(c, n.sons[L-2])
     for i in countup(0, L - 3):
       addLocalDecl(c, n.sons[i], skForVar)
+    openScope(c)
     n.sons[L-1] = semTemplBody(c, n.sons[L-1])
     closeScope(c)
+    closeScope(c)
   of nkBlockStmt, nkBlockExpr, nkBlockType:
     checkSonsLen(n, 2)
     openScope(c)