Cannot parse two ifs

[aartbik]

Fuzzing found a few more missing cases, having two if's does not seem to work yet.

Set<int> globx = {};

@NeverInline
int bar() {
  globx = { if (true) 3,           4 };  // OK
  globx = {           3, if (true) 4 };  // OK
  globx = { if (true) 3, if (true) 4 };  // NOT OK
}

hello.dart:40:13: Error: Expected ':' after this.
  globx = { if (true) 3, if (true) 4 };  // NOT OK
            ^
hello.dart:40:26: Error: Expected ':' after this.
  globx = { if (true) 3, if (true) 4 };  // NOT OK
                         ^

@a-siva

[aartbik]

For what it is worth, fuzzing also found this issue for for-loops.
Also, putting a value in between resolves the issue.

  globx = { for (int i = 0; i < 10; i++) i,  100 };  // OK
  globx = { 0, for (int i = 0; i < 10; i++) 100 + i };  // OK
  globx = { for (int i = 0; i < 10; i++) i,  for (int i = 0; i < 10; i++) 100 + i };  // NOT OK
  globx = { for (int i = 0; i < 10; i++) i,  50, for (int i = 0; i < 10; i++) 100 + i };  // OK AGAIN

hello.dart:42:13: Error: Expected ':' after this.
  globx = { for (int i = 0; i < 10; i++) i,  for (int i = 0; i < 10; i++) 100 + i };  // NOT OK
            ^
hello.dart:42:46: Error: Expected ':' after this.
  globx = { for (int i = 0; i < 10; i++) i,  for (int i = 0; i < 10; i++) 100 + i };  // NOT OK
                                             ^

[aartbik]

Also, not really a bug, but the new syntax gives us a nice classic dangling else problem :-)

globx = [ if (b1) if (b2) 1 else 2 ];

false false : []
false true  : []
true  false : [2]
true  true  : [1]

[lrhn]

This looks like a bug in the inference of whether the literal is a map or a set, as if only top-level elements are counted when trying to see if it's a map or set. The "expected ':' here" message suggests that it is being treated as a map literal.

Since the if branches contain a single value element expression, they should count as a vote for being a set, and the literal should become a set literal.

The "dangling else" issue is a classical parsing ambiguity with C-style if/else. We solve it the same way here as in if statements: Always bind the then to the nearest if without a then. The results you print are as expected.

[chloestefantsova]

Thanks for spotting this! Proposed fix: https://dart-review.googlesource.com/c/sdk/+/98341.