bugfix: immediate templates are preferred consistently (danger: breaks code)

compiler/astalgo.nim

@@ -561,14 +561,31 @@ proc strTableContains(t: TStrTable, n: PSym): bool =
 
 proc strTableRawInsert(data: var TSymSeq, n: PSym) = 
   var h: THash = n.name.h and high(data)
-  while data[h] != nil: 
-    if data[h] == n:
-      # allowed for 'export' feature:
-      #InternalError(n.info, "StrTableRawInsert: " & n.name.s)
-      return
-    h = nextTry(h, high(data))
-  assert(data[h] == nil)
-  data[h] = n
+  if sfImmediate notin n.flags:
+    # fast path:
+    while data[h] != nil:
+      if data[h] == n:
+        # allowed for 'export' feature:
+        #InternalError(n.info, "StrTableRawInsert: " & n.name.s)
+        return
+      h = nextTry(h, high(data))
+    assert(data[h] == nil)
+    data[h] = n
+  else:
+    # slow path; we have to ensure immediate symbols are preferred for
+    # symbol lookups.
+    # consider the chain: foo (immediate), foo, bar, bar (immediate)
+    # then bar (immediate) gets replaced with foo (immediate) and the non
+    # immediate foo is picked! Thus we need to replace it with the first
+    # slot that has in fact the same identifier stored in it!
+    var favPos = -1
+    while data[h] != nil:
+      if data[h] == n: return
+      if favPos < 0 and data[h].name.id == n.name.id: favPos = h
+      h = nextTry(h, high(data))
+    assert(data[h] == nil)
+    data[h] = n
+    if favPos >= 0: swap data[h], data[favPos]
 
 proc symTabReplaceRaw(data: var TSymSeq, prevSym: PSym, newSym: PSym) =
   assert prevSym.name.h == newSym.name.h

compiler/lookups.nim

@@ -339,4 +339,16 @@ proc nextOverloadIter*(o: var TOverloadIter, c: PContext, n: PNode): PSym =
                                    n.sons[0].sym.name, o.inSymChoice)
   
   if result != nil and result.kind == skStub: loadStub(result)
-  
+
+when false:
+  proc qualifiedLookUpPreferImmediate*(c: PContext, n: PNode,
+                                       flags = {checkUndeclared}): PSym =
+    var o: TOverloadIter
+    result = initOverloadIter(o, c, n)
+    var a = result
+    while a != nil:
+      if sfImmediate in a.flags: return a
+      a = nextOverloadIter(o, c, n)
+    if result == nil and checkUndeclared in flags: 
+      localError(n.info, errUndeclaredIdentifier, n.considerAcc.s)
+      result = errorSym(c, n)

tests/template/tprefer_immediate.nim

@@ -0,0 +1,17 @@
+discard """
+  output: '''immediate'''
+"""
+
+# Test that immediate templates are preferred over non-immediate templates
+
+template foo(a, b: expr) = echo "foo expr"
+
+template foo(a, b: int) = echo "foo int"
+template foo(a, b: float) = echo "foo float"
+template foo(a, b: string) = echo "foo string"
+template foo(a, b: expr) {.immediate.} = echo "immediate"
+template foo(a, b: bool) = echo "foo bool"
+template foo(a, b: char) = echo "foo char"
+
+foo(undeclaredIdentifier, undeclaredIdentifier2)
+

todo.txt

@@ -22,7 +22,6 @@ Bugs
 - compilation of niminst takes way too long. looks like a regression
 - docgen: sometimes effects are listed twice
 - 'result' is not properly cleaned for NRVO --> use uninit checking instead
-- sneaking with qualifiedLookup() is really broken!
 - blocks can "export" an identifier but the CCG generates {} for them ...
 - osproc execProcesses can deadlock if all processes fail (as experienced
   in c++ mode)