Avoid adding new unneeded names to blocks in text roundtripping (#4943)

Previously the wat parser would turn this input:

(block
  (nop)
)

into something like this:

(block $block17
  (nop)
)

It just added a name all the time, in case the block is referred to by an index
later even though it doesn't have a name.

This PR makes us rountrip more precisely by not adding such names: if there
was no name before, and there is no break by index, then do not add a name.

In addition, this will be useful for non-nullable locals since whether a block has
a name or not matters there. Like #4912, this makes us more regular in our
usage of block names.

1 files changed, 4 insertions, 6 deletions

diff --git a/test/binaryen.js/optimize-levels.js.txt b/test/binaryen.js/optimize-levels.js.txt
index e8d918a2f..05fe23589 100644
--- a/test/binaryen.js/optimize-levels.js.txt
+++ b/test/binaryen.js/optimize-levels.js.txt
@@ -20,12 +20,10 @@
  (memory $0 0)
  (export "test" (func $test))
  (func $test (param $0 i32) (result i32)
-  (block $block (result i32)
-   (if (result i32)
-    (local.get $0)
-    (local.get $0)
-    (i32.const 0)
-   )
+  (if (result i32)
+   (local.get $0)
+   (local.get $0)
+   (i32.const 0)
   )
  )
 )