Block-local types with the same name can silently give wrong runtime results

[timotheecour]

Block-local types with the same name can silently give wrong runtime results.

this is directly caused by #5170 but hesistant to call it a duplicate because in following case the result is worse:

• no warning, no error
• wrong results at runtime; and this could be detected only in production (eg in following case, you'd never know there was a bug until you tried a value > int8.max)

Example

  type Foo = object
    bar: int8
  var f1: Foo
  block:
    type Foo = object
      bar: int
    var f2 = Foo(bar: 300)
    echo f2.bar # prints 44 instead of 300

Current Output

44

Expected Output

300

Additional Information

• latest devel 574f613
• directly caused by Block-local types with the same name lead to bad codegen (sighashes regression) #5170

[juancarlospaco]

Should type declarations be allowed inside blocks ?, Whats does it solves?.

[timotheecour]

that feature is used heavily, removing it would be a pointless breaking change; it's a sensible feature IMO, for scoping (eg very useful in tests, but not just that)

[narimiran]

@timotheecour why the hell your code examples (in multiple issues that I've opened) have indentation??

Maybe it is indented in your files so it is easier and faster for you to just copy-paste them as they are, but it is harder and slower for everybody else to reproduce it.
Please, slow yourself down, read and double-check both your issues and PRs before submitting them, remove all unneeded stuff, fix quirks, and only then post them.

Thank you in advance.

[narimiran]

this is directly caused by #5170 but hesistant to call it a duplicate because in following case the result is worse

To me it looks like a duplicate. In all cases the wrong Foo is picked up, and now we're making different examples of the same behaviour: one is Foo with different field (baz vs bar), other is with different int type (int8 vs int) and the last one is with different types (array vs int).