fixes #2481

compiler/semdata.nim

@@ -43,7 +43,8 @@ type
     inst*: PInstantiation
 
   TExprFlag* = enum
-    efLValue, efWantIterator, efInTypeof, efWantStmt, efDetermineType,
+    efLValue, efWantIterator, efInTypeof,
+    efWantStmt, efAllowStmt, efDetermineType,
     efAllowDestructor, efWantValue, efOperand, efNoSemCheck
   TExprFlags* = set[TExprFlag]
 

compiler/semexprs.nim

@@ -31,7 +31,7 @@ proc semOperand(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   if result.typ != nil:
     # XXX tyGenericInst here?
     if result.typ.kind == tyVar: result = newDeref(result)
-  elif efWantStmt in flags:
+  elif {efWantStmt, efAllowStmt} * flags != {}:
     result.typ = newTypeS(tyEmpty, c)
   else:
     localError(n.info, errExprXHasNoType,

compiler/sigmatch.nim

@@ -1422,9 +1422,12 @@ proc prepareOperand(c: PContext; formal: PType; a: PNode): PNode =
     # a.typ == nil is valid
     result = a
   elif a.typ.isNil:
+    # XXX This is unsound! 'formal' can differ from overloaded routine to
+    # overloaded routine!
     let flags = if formal.kind == tyIter: {efDetermineType, efWantIterator}
-                elif formal.kind == tyStmt: {efDetermineType, efWantStmt}
+                else: {efDetermineType, efAllowStmt}
-                else: {efDetermineType}
+                #elif formal.kind == tyStmt: {efDetermineType, efWantStmt}
+                #else: {efDetermineType}
     result = c.semOperand(c, a, flags)
   else:
     result = a

tests/overload/tstmtoverload.nim

@@ -0,0 +1,38 @@
+
+# bug #2481
+import math
+
+template test(loopCount: int, extraI: int, testBody: stmt): stmt =
+  block:
+    for i in 0..loopCount-1:
+      testBody
+    echo "done extraI=", extraI
+
+template test(loopCount: int, extraF: float, testBody: stmt): stmt =
+  block:
+    test(loopCount, round(extraF), testBody)
+
+template test(loopCount: int, testBody: stmt): stmt =
+  block:
+    test(loopCount, 0, testBody)
+    echo "done extraI passed 0"
+
+when isMainModule:
+  var
+    loops = 0
+
+  test 0, 0:
+    loops += 1
+  echo "test 0 complete, loops=", loops
+
+  test 1, 1.0:
+    loops += 1
+  echo "test 1.0 complete, loops=", loops
+
+  when true:
+    # when true we get the following compile time error:
+    #   b.nim(35, 6) Error: expression 'loops += 1' has no type (or is ambiguous)
+    loops = 0
+    test 2:
+      loops += 1
+    echo "test no extra complete, loops=", loops