fixes #250

compiler/ast.nim

@@ -726,7 +726,7 @@ const
   nkSymChoices* = {nkClosedSymChoice, nkOpenSymChoice}
   nkStrKinds* = {nkStrLit..nkTripleStrLit}
 
-  skLocalVars* = {skVar, skLet, skForVar, skParam}
+  skLocalVars* = {skVar, skLet, skForVar, skParam, skResult}
 
 
 # creator procs:

compiler/msgs.nim

@@ -104,7 +104,7 @@ type
     warnUnknownSubstitutionX, warnLanguageXNotSupported, warnCommentXIgnored, 
     warnNilStatement, warnAnalysisLoophole,
     warnDifferentHeaps, warnWriteToForeignHeap, warnImplicitClosure,
-    warnEachIdentIsTuple, warnUser,
+    warnEachIdentIsTuple, warnShadowIdent, warnUser,
     hintSuccess, hintSuccessX, 
     hintLineTooLong, hintXDeclaredButNotUsed, hintConvToBaseNotNeeded, 
     hintConvFromXtoItselfNotNeeded, hintExprAlwaysX, hintQuitCalled, 
@@ -351,6 +351,7 @@ const
     warnWriteToForeignHeap: "write to foreign heap [WriteToForeignHeap]",
     warnImplicitClosure: "implicit closure convention: '$1' [ImplicitClosure]",
     warnEachIdentIsTuple: "each identifier is a tuple [EachIdentIsTuple]",
+    warnShadowIdent: "shadowed identifier: '$1' [ShadowIdent]",
     warnUser: "$1 [User]", 
     hintSuccess: "operation successful [Success]", 
     hintSuccessX: "operation successful ($# lines compiled; $# sec total; $#) [SuccessX]", 
@@ -370,14 +371,14 @@ const
     hintUser: "$1 [User]"]
 
 const
-  WarningsToStr*: array[0..18, string] = ["CannotOpenFile", "OctalEscape", 
+  WarningsToStr*: array[0..19, string] = ["CannotOpenFile", "OctalEscape", 
     "XIsNeverRead", "XmightNotBeenInit",
     "Deprecated", "ConfigDeprecated",
     "SmallLshouldNotBeUsed", "UnknownMagic", 
     "RedefinitionOfLabel", "UnknownSubstitutionX", "LanguageXNotSupported", 
     "CommentXIgnored", "NilStmt",
     "AnalysisLoophole", "DifferentHeaps", "WriteToForeignHeap",
-    "ImplicitClosure", "EachIdentIsTuple", "User"]
+    "ImplicitClosure", "EachIdentIsTuple", "ShadowIdent", "User"]
 
   HintsToStr*: array[0..15, string] = ["Success", "SuccessX", "LineTooLong", 
     "XDeclaredButNotUsed", "ConvToBaseNotNeeded", "ConvFromXtoItselfNotNeeded", 
@@ -464,7 +465,7 @@ proc raiseRecoverableError*(msg: string) {.noinline, noreturn.} =
   raise newException(ERecoverableError, msg)
 
 var
-  gNotes*: TNoteKinds = {low(TNoteKind)..high(TNoteKind)}
+  gNotes*: TNoteKinds = {low(TNoteKind)..high(TNoteKind)} - {warnShadowIdent}
   gErrorCounter*: int = 0     # counts the number of errors
   gHintCounter*: int = 0
   gWarnCounter*: int = 0

compiler/semstmts.nim

@@ -237,7 +237,9 @@ proc semVarOrLet(c: PContext, n: PNode, symkind: TSymKind): PNode =
         if c.InUnrolledContext > 0: v.flags.incl(sfShadowed)
         else:
           let shadowed = findShadowedVar(c, v)
-          if shadowed != nil: shadowed.flags.incl(sfShadowed)
+          if shadowed != nil:
+            shadowed.flags.incl(sfShadowed)
+            Message(a.info, warnShadowIdent, v.name.s)
       if def != nil and def.kind != nkEmpty:
         # this is only needed for the evaluation pass:
         v.ast = def

doc/nimrodc.txt

@@ -37,6 +37,38 @@ Advanced command line switches are:
 .. include:: advopt.txt
 
 
+
+List of warnings
+----------------
+
+Each warning can be activated individually with ``--warning[NAME]:on|off`` or
+in a ``push`` pragma. 
+
+==========================       ============================================
+Name                             Description
+==========================       ============================================
+CannotOpenFile                   Some file not essential for the compiler's
+                                 working could not be opened.
+OctalEscape                      The code contains an unsupported octal 
+                                 sequence.
+Deprecated                       The code uses a deprecated symbol.
+ConfigDeprecated                 The project makes use of a deprecated config
+                                 file.
+SmallLshouldNotBeUsed            The letter 'l' should not be used as an 
+                                 identifier.
+AnalysisLoophole                 The thread analysis was incomplete due to
+                                 an indirect call.
+DifferentHeaps                   The code mixes different local heaps in a
+                                 very dangerous way.
+WriteToForeignHeap               The code contains a threading error. 
+EachIdentIsTuple                 The code contains a confusing ``var`` 
+                                 declaration.
+ShadowIdent                      A local variable shadows another local 
+                                 variable of an outer scope.
+User                             Some user defined warning.
+==========================       ============================================
+
+
 Configuration files
 -------------------
 

lib/impure/db_mongo.nim

@@ -34,8 +34,8 @@ type
   TDbConn* = TMongo    ## a database connection; alias for ``TMongo``
 
   FDb* = object of FIO ## effect that denotes a database operation
-  FReadDb* = object of FReadIO   ## effect that denotes a read operation
+  FReadDb* = object of FDB   ## effect that denotes a read operation
-  FWriteDb* = object of FWriteIO ## effect that denotes a write operation
+  FWriteDb* = object of FDB  ## effect that denotes a write operation
 
 proc dbError*(db: TDbConn, msg: string) {.noreturn.} = 
   ## raises an EDb exception with message `msg`.

lib/impure/db_mysql.nim

@@ -20,8 +20,8 @@ type
   TSqlQuery* = distinct string ## an SQL query string
 
   FDb* = object of FIO ## effect that denotes a database operation
-  FReadDb* = object of FReadIO   ## effect that denotes a read operation
+  FReadDb* = object of FDb   ## effect that denotes a read operation
-  FWriteDb* = object of FWriteIO ## effect that denotes a write operation
+  FWriteDb* = object of FDb  ## effect that denotes a write operation
 
 proc dbError(db: TDbConn) {.noreturn.} = 
   ## raises an EDb exception.

lib/impure/db_postgres.nim

@@ -20,8 +20,8 @@ type
   TSqlQuery* = distinct string ## an SQL query string
 
   FDb* = object of FIO ## effect that denotes a database operation
-  FReadDb* = object of FReadIO   ## effect that denotes a read operation
+  FReadDb* = object of FDB   ## effect that denotes a read operation
-  FWriteDb* = object of FWriteIO ## effect that denotes a write operation
+  FWriteDb* = object of FDB  ## effect that denotes a write operation
   
 proc sql*(query: string): TSqlQuery {.noSideEffect, inline.} =  
   ## constructs a TSqlQuery from the string `query`. This is supposed to be 

lib/impure/db_sqlite.nim

@@ -20,8 +20,8 @@ type
   TSqlQuery* = distinct string ## an SQL query string
   
   FDb* = object of FIO ## effect that denotes a database operation
-  FReadDb* = object of FReadIO   ## effect that denotes a read operation
+  FReadDb* = object of FDB   ## effect that denotes a read operation
-  FWriteDb* = object of FWriteIO ## effect that denotes a write operation
+  FWriteDb* = object of FDB  ## effect that denotes a write operation
   
 proc sql*(query: string): TSqlQuery {.noSideEffect, inline.} =  
   ## constructs a TSqlQuery from the string `query`. This is supposed to be 

lib/system/ansi_c.nim

@@ -35,6 +35,7 @@ var
   c_stderr {.importc: "stderr", noDecl.}: C_TextFileStar
 
 # constants faked as variables:
+when not defined(SIGINT):
   var 
     SIGINT {.importc: "SIGINT", nodecl.}: cint
     SIGSEGV {.importc: "SIGSEGV", nodecl.}: cint
@@ -95,6 +96,7 @@ proc c_malloc(size: int): pointer {.importc: "malloc", nodecl.}
 proc c_free(p: pointer) {.importc: "free", nodecl.}
 proc c_realloc(p: pointer, newsize: int): pointer {.importc: "realloc", nodecl.}
 
+when not defined(errno):
   var errno {.importc, header: "<errno.h>".}: cint ## error variable
 proc strerror(errnum: cint): cstring {.importc, header: "<string.h>".}
 

todo.txt

@@ -152,7 +152,8 @@ Version 2 and beyond
   "stop the world". However, it may be worthwhile to generate explicit 
   (or implicit) syncGC() calls in loops. Automatic loop injection seems
   troublesome, but maybe we can come up with a simple heuristic. (All procs
-  that `new` shared memory are syncGC() candidates...)
+  that `new` shared memory are syncGC() candidates... But then 'new' itself
+  calls syncGC() so that's pointless.)
 
 - const ptr/ref  --> pointless because of aliasing; 
   much better: 'writes: []' effect

web/news.txt

@@ -27,6 +27,8 @@ Changes affecting backwards compatibility
 Compiler Additions
 ------------------
 
+- The compiler can now warn about shadowed local variables. However, this needs
+  to be turned on explicitly via ``--warning[ShadowIdent]:on``.
 
 
 Language Additions