make error messages render Nim code, not NIF code

src/hexer/duplifier.nim

@@ -32,7 +32,7 @@ It follows that we're only interested in Call expressions here, or similar
 import std / [assertions]
 include nifprelude
 import nifindexes, symparser, treemangler, lifter, mover
-import ".." / nimony / [nimony_model, programs, decls, typenav]
+import ".." / nimony / [nimony_model, programs, decls, typenav, renderer]
 
 type
   Context = object
@@ -604,7 +604,7 @@ proc trEnsureMove(c: var Context; n: var Cursor; e: Expects) =
     copyInto c.dest, n:
       tr c, n, e
   else:
-    let m = "not the last usage of: " & toString(n, false)
+    let m = "not the last usage of: " & asNimCode(n)
     c.dest.buildTree ErrT, info:
       c.dest.add strToken(pool.strings.getOrIncl(m), info)
   skip n

src/lib/filelinecache.nim

@@ -0,0 +1,56 @@
+#       Nif library
+# (c) Copyright 2024 Andreas Rumpf
+#
+# See the file "license.txt", included in this
+# distribution, for details about the copyright.
+
+## Logic for mapping a (file, line, col) key to the file's content.
+
+import std / syncio
+import std/[tables, strutils]
+
+type
+  CachedFile* = object
+    content: string
+    lineStarts: seq[int]
+
+  FilePosition* = object
+    line*: int
+    col*: int
+
+  FileLineCache = object
+    files: Table[string, CachedFile]
+
+var
+  gFileLineCache: FileLineCache
+
+proc loadFile*(filename: string) =
+  var entry = CachedFile(content: readFile(filename), lineStarts: @[0])
+  var nl = find(entry.content, '\n')
+  while nl > 0:
+    entry.lineStarts.add nl
+    nl = find(entry.content, '\n', nl + 1)
+  gFileLineCache.files[filename] = ensureMove entry
+
+proc extract*(filename: string; start, finish: FilePosition): string =
+  if not gFileLineCache.files.hasKey(filename):
+    loadFile(filename)
+  let entry {.cursor.} = gFileLineCache.files[filename]
+  let startIdx = entry.lineStarts[start.line-1] + start.col-1
+  let finishIdx = entry.lineStarts[finish.line-1] + finish.col-1
+  result = entry.content[startIdx..finishIdx]
+
+proc extract*(filename: string; start: FilePosition): string =
+  if not gFileLineCache.files.hasKey(filename):
+    loadFile(filename)
+  let entry {.cursor.} = gFileLineCache.files[filename]
+  let startIdx = entry.lineStarts[start.line-1] + start.col-1
+  if start.line < entry.lineStarts.len:
+    let finishIdx = entry.lineStarts[start.line]-1
+    result = entry.content[startIdx..finishIdx]
+  else:
+    result = entry.content.substr(startIdx)
+
+when isMainModule:
+  echo extract("src/lib/filelinecache.nim", FilePosition(line: 1, col: 9), FilePosition(line: 3, col: 2))
+  echo extract("src/lib/filelinecache.nim", FilePosition(line: 1, col: 9))

src/nifc/nim.cfg

@@ -3,3 +3,5 @@
 # instead of the directory of this nim.cfg file.
 --outdir: "bin"
 --styleCheck: off
+# Make NIFC more robust against broken NIF inputs:
+--define: showBroken

src/nimony/derefs.nim

@@ -25,7 +25,7 @@ import std / [assertions]
 
 include nifprelude
 
-import nimony_model, programs, decls, typenav, sembasics, reporters
+import nimony_model, programs, decls, typenav, sembasics, reporters, renderer
 
 type
   Expects = enum
@@ -218,7 +218,7 @@ proc trReturn(c: var Context; n: var Cursor) =
   else:
     let err = c.r.returnType == WantVarTResult and not validBorrowsFrom(c, n)
     if err:
-      buildLocalErr(c.dest, n.info, "cannot borrow from " & toString(n, false))
+      buildLocalErr(c.dest, n.info, "cannot borrow from " & asNimCode(n))
     else:
       tr c, n, c.r.returnType
   takeParRi c, n
@@ -228,7 +228,7 @@ proc mightBeDangerous(c: var Context; n: Cursor) =
   if root != NoSymId:
     for d in items(c.r.dangerousLocations):
       if d[0] == root:
-        buildLocalErr c.dest, n.info, "cannot mutate " & toString(n, false) &
+        buildLocalErr c.dest, n.info, "cannot mutate " & asNimCode(n) &
           "; binding created here: " & infoToStr(d[1].info)
 
 proc checkForDangerousLocations(c: var Context; n: var Cursor) =
@@ -414,10 +414,10 @@ proc trAsgn(c: var Context; n: var Cursor) =
     tr c, n, e
   case err
   of InvalidBorrow:
-    buildLocalErr c.dest, n.info, "cannot borrow from " & toString(n, false)
+    buildLocalErr c.dest, n.info, "cannot borrow from " & asNimCode(n)
     skip n
   of LocationIsConst:
-    buildLocalErr c.dest, n.info, "cannot mutate expression " & toString(n, false)
+    buildLocalErr c.dest, n.info, "cannot mutate expression " & asNimCode(n)
     tr c, n, e
     tr c, n, e
   else:

src/nimony/expreval.nim

@@ -9,7 +9,7 @@
 import std / assertions
 
 include nifprelude
-import nimony_model, decls, programs, xints, semdata
+import nimony_model, decls, programs, xints, semdata, renderer
 
 type
   EvalContext* = object
@@ -111,11 +111,11 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
         skipToEnd n
         return a
       elif a.exprKind != TrueX:
-        error "expected bool for operand of `and` but got: " & toString(a, false), n.info
+        error "expected bool for operand of `and` but got: " & asNimCode(a), n.info
         return
       let b = propagateError eval(c, n)
       if not isConstBoolValue(b):
-        error "expected bool for operand of `and` but got: " & toString(b, false), n.info
+        error "expected bool for operand of `and` but got: " & asNimCode(b), n.info
         return
       else:
         skipParRi n
@@ -127,11 +127,11 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
         skipToEnd n
         return a
       elif a.exprKind != FalseX:
-        error "expected bool for operand of `or` but got: " & toString(a, false), n.info
+        error "expected bool for operand of `or` but got: " & asNimCode(a), n.info
         return
       let b = propagateError eval(c, n)
       if not isConstBoolValue(b):
-        error "expected bool for operand of `or` but got: " & toString(b, false), n.info
+        error "expected bool for operand of `or` but got: " & asNimCode(b), n.info
         return
       else:
         skipParRi n
@@ -146,7 +146,7 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
         skipParRi n
         return c.getTrueValue()
       else:
-        error "expected bool for operand of `not` but got: " & toString(a, false), n.info
+        error "expected bool for operand of `not` but got: " & asNimCode(a), n.info
         return
     of SufX:
       # we only need raw value
@@ -157,7 +157,7 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
       inc n
       skipParRi n
       if c.c == nil:
-        error "cannot evaluate expression at compile time: " & toString(n, false), n.info
+        error "cannot evaluate expression at compile time: " & asNimCode(n), n.info
       elif IsMain in c.c.moduleFlags:
         result = c.getTrueValue()
       else:
@@ -167,9 +167,9 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
         result = n
         skip n
       else:
-        error "cannot evaluate expression at compile time: " & toString(n, false), n.info
+        error "cannot evaluate expression at compile time: " & asNimCode(n), n.info
   else:
-    error "cannot evaluate expression at compile time: " & toString(n, false), n.info
+    error "cannot evaluate expression at compile time: " & asNimCode(n), n.info
 
 proc evalExpr*(c: var SemContext, n: var Cursor): TokenBuf =
   var ec = initEvalContext(addr c)
@@ -271,7 +271,7 @@ proc bitsetSizeInBytes*(baseType: Cursor): xint =
     var index = baseType
     inc index # tag
     skip index # basetype
-    # XXX offset not implemented 
+    # XXX offset not implemented
     skip index # lo
     let hi = evalOrdinal(nil, index)
     var err = false

src/nimony/renderer.nim

@@ -0,0 +1,53 @@
+#       Nimony
+# (c) Copyright 2024 Andreas Rumpf
+#
+# See the file "license.txt", included in this
+# distribution, for details about the copyright.
+
+import ".." / lib / [bitabs, lineinfos, nifstreams, nifcursors, filelinecache]
+
+## Rendering of Nim code from a cursor.
+
+proc asNimCode*(n: Cursor): string =
+  var m0: PackedLineInfo = NoLineInfo
+  var m1: PackedLineInfo = NoLineInfo
+  var nested = 0
+  var n2 = n
+  var file0 = FileId 0
+  while true:
+    if n2.info.isValid:
+      let currentFile = getFileId(pool.man, n2.info)
+      if not m0.isValid:
+        m0 = n2.info
+        file0 = currentFile
+      elif not m1.isValid and currentFile == file0:
+        m1 = n2.info
+    case n2.kind
+    of ParLe:
+      inc nested
+    of ParRi:
+      dec nested
+    else:
+      discard
+    if nested == 0: break
+    inc n2
+
+  when false: #if m0.isValid:
+    let (_, line0, col0) = unpack(pool.man, m0)
+    if m1.isValid:
+      let (_, line1, col1) = unpack(pool.man, m1)
+      result = extract(pool.files[file0],
+                       FilePosition(line: line0, col: col0),
+                       FilePosition(line: line1, col: col1))
+    else:
+      result = extract(pool.files[file0], FilePosition(line: line0, col: col0))
+    var visible = false
+    for i in 0..<result.len:
+      if result[i] > ' ':
+        visible = true
+        break
+    if not visible:
+      result = toString(n, false)
+  else:
+    # Fallback to the NIF representation as it is much better than nothing:
+    result = toString(n, false)

src/nimony/sem.nim

@@ -13,7 +13,7 @@ include nifprelude
 import nimony_model, symtabs, builtintypes, decls, symparser, asthelpers,
   programs, sigmatch, magics, reporters, nifconfig, nifindexes,
   intervals, xints, typeprops,
-  semdata, sembasics, semos, expreval, semborrow, enumtostr, derefs, sizeof
+  semdata, sembasics, semos, expreval, semborrow, enumtostr, derefs, sizeof, renderer
 
 import ".." / gear2 / modnames
 import ".." / models / tags
@@ -636,7 +636,7 @@ proc semConstBoolExpr(c: var SemContext; n: var Cursor) =
     if value.kind == ParLe and value.tagId == ErrT:
       c.dest.add valueBuf
     else:
-      buildErr c, it.n.info, "expected constant bool value but got: " & toString(value, false)
+      buildErr c, it.n.info, "expected constant bool value but got: " & asNimCode(value)
   else:
     c.dest.shrink start
     c.dest.add valueBuf
@@ -656,7 +656,7 @@ proc semConstStrExpr(c: var SemContext; n: var Cursor) =
     if value.kind == ParLe and value.tagId == ErrT:
       c.dest.add valueBuf
     else:
-      buildErr c, it.n.info, "expected constant string value but got: " & toString(value, false)
+      buildErr c, it.n.info, "expected constant string value but got: " & asNimCode(value)
   else:
     c.dest.shrink start
     c.dest.add valueBuf
@@ -676,7 +676,7 @@ proc semConstIntExpr(c: var SemContext; n: var Cursor) =
     if value.kind == ParLe and value.tagId == ErrT:
       c.dest.add valueBuf
     else:
-      buildErr c, it.n.info, "expected constant integer value but got: " & toString(value, false)
+      buildErr c, it.n.info, "expected constant integer value but got: " & asNimCode(value)
   else:
     c.dest.shrink start
     c.dest.add valueBuf
@@ -4442,7 +4442,7 @@ proc semDefined(c: var SemContext; it: var Item) =
   let name = getDottedIdent(it.n)
   skipParRi it.n
   if name == "":
-    c.buildErr info, "invalid expression for defined: " & toString(orig, false), orig
+    c.buildErr info, "invalid expression for defined: " & asNimCode(orig), orig
   else:
     let isDefined = name in c.g.config.defines
     let beforeExpr = c.dest.len
@@ -4474,7 +4474,7 @@ proc semDeclared(c: var SemContext; it: var Item) =
     skipToEnd it.n
   skipParRi it.n
   if nameId == StrId(0):
-    c.buildErr info, "invalid expression for declared: " & toString(orig, false), orig
+    c.buildErr info, "invalid expression for declared: " & asNimCode(orig), orig
   else:
     let isDeclared = isDeclared(c, nameId)
     let beforeExpr = c.dest.len
@@ -5015,7 +5015,7 @@ proc semAddr(c: var SemContext; it: var Item) =
   if isAddressable(a):
     endRead c.dest
   else:
-    let asStr = toString(a, false)
+    let asStr = asNimCode(a)
     endRead c.dest
     c.dest.shrink beforeArg
     c.buildErr info, "invalid expression for `addr` operation: " & asStr
@@ -5063,7 +5063,7 @@ proc semPragmaLine(c: var SemContext; it: var Item; info: PackedLineInfo) =
     var args = newSeq[string]()
     while it.n.kind != ParRi:
       if it.n.kind != StringLit:
-        buildErr c, it.n.info, "expected `string` but got: " & toString(it.n)
+        buildErr c, it.n.info, "expected `string` but got: " & asNimCode(it.n)
 
       args.add pool.strings[it.n.litId]
       inc it.n

src/nimony/sigmatch.nim

@@ -8,7 +8,7 @@ import std / [sets, tables, assertions]
 
 import bitabs, nifreader, nifstreams, nifcursors, lineinfos
 
-import nimony_model, decls, programs, semdata, typeprops, xints, builtintypes
+import nimony_model, decls, programs, semdata, typeprops, xints, builtintypes, renderer
 
 type
   Item* = object
@@ -70,7 +70,7 @@ proc concat(a: varargs[string]): string =
   for i in 1..high(a): result.add a[i]
 
 proc typeToString*(n: Cursor): string =
-  result = toString(n, false)
+  result = asNimCode(n)
 
 proc error(m: var Match; k: MatchErrorKind; expected, got: Cursor) =
   if m.err: return # first error is the important one