Missing type inference in loop + case + if + continue

[arnetheduck]

Description

broken:

for i in 0..<10:
  let x =
    case false
    of true:
      42
    of false:
      if true:
        continue
      else:
        raiseAssert "Won't get here"

  echo x

works:

for i in 0..<10:
  let x =
    case false
    of true:
      42
    of false:
      if true:
        33
      else:
        raiseAssert "Won't get here"

  echo x

Nim Version

1.6.14

Current Output

testit.nim(12, 7) Error: expression '42' is of type 'int literal(42)' and has to be used (or discarded)

Expected Output

No response

Possible Solution

No response

Additional Information

No response

[metagn]

The noreturn checks are not deep IIRC, they just check the last node in a branch, then check if it's a noreturn call or continue/raise/return/break. In this case the last node is an if statement with 2 noreturn branches, which isn't inferred to be noreturn.

Nim/compiler/sem.nim

Lines 209 to 215 in b3912c2

	proc endsInNoReturn(n: PNode): bool =
	# check if expr ends in raise exception or call of noreturn proc
	var it = n
	while it.kind in {nkStmtList, nkStmtListExpr} and it.len > 0:
	it = it.lastSon
	result = it.kind in nkLastBlockStmts or
	it.kind in nkCallKinds and it[0].kind == nkSym and sfNoReturn in it[0].sym.flags