fixes #22673; Cannot prove that result is initialized for a placehold… (#22915)

…er base method returning a lent

fixes #22673

(cherry picked from commit 2e070dfc76)

compiler/cgmeth.nim

@@ -95,7 +95,8 @@ proc sameMethodBucket(a, b: PSym; multiMethods: bool): MethodResult =
       return No
   if result == Yes:
     # check for return type:
-    if not sameTypeOrNil(a.typ[0], b.typ[0]):
+    # ignore flags of return types; # bug #22673
+    if not sameTypeOrNil(a.typ[0], b.typ[0], {IgnoreFlags}):
       if b.typ[0] != nil and b.typ[0].kind == tyUntyped:
         # infer 'auto' from the base to make it consistent:
         b.typ[0] = a.typ[0]

compiler/types.nim

@@ -991,7 +991,7 @@ type
     ExactGcSafety
     AllowCommonBase
     PickyCAliases  # be picky about the distinction between 'cint' and 'int32'
-    IgnoreFlags          # used for borrowed functions; ignores the tfVarIsPtr flag
+    IgnoreFlags    # used for borrowed functions and methods; ignores the tfVarIsPtr flag
 
   TTypeCmpFlags* = set[TTypeCmpFlag]
 

tests/method/t22673.nim

@@ -0,0 +1,21 @@
+discard """
+  matrix: "--warningAsError:UseBase"
+"""
+
+# bug #22673
+type RefEntry = ref object of RootObj
+
+type RefFile = ref object of RefEntry
+    filename*: string
+    data*: string
+
+type RefDir = ref object of RefEntry
+    dirname*: string
+    files*: seq[RefFile]
+
+method name*(e: RefEntry): lent string {.base.} =
+  raiseAssert "Don't call the base method"
+
+method name*(e: RefFile): lent string = e.filename
+
+method name*(e: RefDir): lent string = e.dirname