RangeInfo: disallow expressions with non-void type at the start or the end of multi-statement selections.

[nkcsgexi]

No description provided.

[nkcsgexi]

@swift-ci please smoke test

[jrose-apple]

What happens when someone has a call to a @discardableResult function?

@discardableResult func foo() -> Bool { return true }
func test() {
  foo() // non-void type!
}

[nkcsgexi]

oh, that's a good point. I think we should allow this as a special case.

[jrose-apple]

Please don't special-case it syntactically. I think you just need a better test for "top-level expression". Maybe it makes more sense to say "they must all be children of the same BraceStmt"?

[jrose-apple]

After all, selecting from outside an if and going only halfway in wouldn't be valid either.

[nkcsgexi]

@jrose-apple I think "children of the same BraceStmt" is a better criterion here. I'll rework this patch. 👍

[nkcsgexi]

@jrose-apple hmm, actually this approach works well on other cases but not so much inside switch statements, for two reasons: (1) switch statement encloses directly case clauses, no brace stmt is involved; (2) case stmt can also enclose valid multi-statement selection without brace stmt in between.

[jrose-apple]

CaseStmts use BraceStmt too, it's just implicit:

func test(x: Int) {
  switch x {
  case 1:
    1
  default:
    0
  }
}

(source_file
  (func_decl "test(x:)" interface type='(Int) -> ()' access=internal
    (parameter_list
      (parameter "x" apiName=x type='Int' interface type='Int'))
    (brace_stmt
      (switch_stmt
        (declref_expr type='Int' location=<stdin>:2:10 range=[<stdin>:2:10 - line:2:10] decl=main.(file).func decl.x@<stdin>:1:11 function_ref=unapplied specialized=no)
        (case_stmt
          (case_label_item
          (pattern_expr type='Int'
            (call_expr implicit type='Int1' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] nothrow arg_labels=
              (dot_syntax_call_expr implicit type='() -> Int1' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] nothrow
                (declref_expr implicit type='(Bool) -> () -> Int1' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] decl=Swift.(file).Bool._getBuiltinLogicValue() function_ref=double specialized=no)
                (binary_expr implicit type='Bool' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] nothrow
                  (declref_expr implicit type='(Int, Int) -> Bool' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] decl=Swift.(file).~= [with Int[Int: Equatable module Swift]] function_ref=compound specialized=no)
                  (tuple_expr implicit type='(Int, Int)' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8]
                    (call_expr implicit type='Int' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] nothrow arg_labels=_builtinIntegerLiteral:
                      (constructor_ref_call_expr implicit type='(Int2048) -> Int' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] nothrow
                        (declref_expr implicit type='(Int.Type) -> (Int2048) -> Int' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] decl=Swift.(file).Int.init(_builtinIntegerLiteral:) function_ref=single specialized=no)
                        (type_expr implicit type='Int.Type' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] typerepr='Int'))
                      (tuple_expr implicit type='(_builtinIntegerLiteral: Int2048)' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] names=_builtinIntegerLiteral
                        (integer_literal_expr type='Int2048' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] value=1)))
                    (declref_expr implicit type='Int' location=<stdin>:3:8 range=[<stdin>:3:8 - line:3:8] decl=main.(file).func decl.$match@<stdin>:3:8 function_ref=unapplied specialized=no))))
              (tuple_expr implicit type='()'))))
          (brace_stmt
            (call_expr implicit type='Int' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] nothrow arg_labels=_builtinIntegerLiteral:
              (constructor_ref_call_expr implicit type='(Int2048) -> Int' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] nothrow
                (declref_expr implicit type='(Int.Type) -> (Int2048) -> Int' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] decl=Swift.(file).Int.init(_builtinIntegerLiteral:) function_ref=single specialized=no)
                (type_expr implicit type='Int.Type' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] typerepr='Int'))
              (tuple_expr implicit type='(_builtinIntegerLiteral: Int2048)' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] names=_builtinIntegerLiteral
                (integer_literal_expr type='Int2048' location=<stdin>:4:5 range=[<stdin>:4:5 - line:4:5] value=1)))))
        (case_stmt
          (case_label_item
          (pattern_any type='Int'))
          (brace_stmt
            (call_expr implicit type='Int' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] nothrow arg_labels=_builtinIntegerLiteral:
              (constructor_ref_call_expr implicit type='(Int2048) -> Int' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] nothrow
                (declref_expr implicit type='(Int.Type) -> (Int2048) -> Int' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] decl=Swift.(file).Int.init(_builtinIntegerLiteral:) function_ref=single specialized=no)
                (type_expr implicit type='Int.Type' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] typerepr='Int'))
              (tuple_expr implicit type='(_builtinIntegerLiteral: Int2048)' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] names=_builtinIntegerLiteral
                (integer_literal_expr type='Int2048' location=<stdin>:6:5 range=[<stdin>:6:5 - line:6:5] value=0)))))))))

I think we deliberately don't have any other grouping mechanism for statements. (Decls are another story. And top-level code makes this confusing.)