Require `then` and `else` with `if` (#6201)

We previously supported (and primarily used) a non-standard text format for
conditionals in which the condition, if-true expression, and if-false expression
were all simply s-expression children of the `if` expression. The standard text
format, however, requires the use of `then` and `else` forms to introduce the
if-true and if-false arms of the conditional. Update the legacy text parser to
require the standard format and update all tests to match. Update the printer to
print the standard format as well.

The .wast and .wat test inputs were mechanically updated with this script:
https://gist.github.com/tlively/85ae7f01f92f772241ec994c840ccbb1

1 files changed, 38 insertions, 20 deletions

diff --git a/test/lit/passes/remove-unused-brs_all-features.wast b/test/lit/passes/remove-unused-brs_all-features.wast
index 344fbe12f..98f020274 100644
--- a/test/lit/passes/remove-unused-brs_all-features.wast
+++ b/test/lit/passes/remove-unused-brs_all-features.wast
@@ -33,25 +33,33 @@
  ;; CHECK:      (func $foo (type $3) (result (ref null $struct))
  ;; CHECK-NEXT:  (if (result (ref null $struct))
  ;; CHECK-NEXT:   (i32.const 1)
- ;; CHECK-NEXT:   (struct.new $struct
- ;; CHECK-NEXT:    (array.new_default $vector
- ;; CHECK-NEXT:     (i32.const 1)
+ ;; CHECK-NEXT:   (then
+ ;; CHECK-NEXT:    (struct.new $struct
+ ;; CHECK-NEXT:     (array.new_default $vector
+ ;; CHECK-NEXT:      (i32.const 1)
+ ;; CHECK-NEXT:     )
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:   )
- ;; CHECK-NEXT:   (ref.null none)
+ ;; CHECK-NEXT:   (else
+ ;; CHECK-NEXT:    (ref.null none)
+ ;; CHECK-NEXT:   )
  ;; CHECK-NEXT:  )
  ;; CHECK-NEXT: )
  (func $foo (result (ref null $struct))
   (if (result (ref null $struct))
    (i32.const 1)
-   (struct.new $struct
-    ;; regression test for computing the cost of an array.new_default, which
-    ;; lacks the optional field "init"
-    (array.new_default $vector
-     (i32.const 1)
+   (then
+    (struct.new $struct
+     ;; regression test for computing the cost of an array.new_default, which
+     ;; lacks the optional field "init"
+     (array.new_default $vector
+      (i32.const 1)
+     )
     )
    )
-   (ref.null $struct)
+   (else
+    (ref.null $struct)
+   )
   )
  )
 
@@ -59,15 +67,19 @@
  ;; CHECK-NEXT:  (loop $loop (result f64)
  ;; CHECK-NEXT:   (if (result f64)
  ;; CHECK-NEXT:    (i32.const 1)
- ;; CHECK-NEXT:    (f64.const 0)
- ;; CHECK-NEXT:    (block $block (result f64)
- ;; CHECK-NEXT:     (nop)
- ;; CHECK-NEXT:     (br_if $loop
- ;; CHECK-NEXT:      (i32.eqz
- ;; CHECK-NEXT:       (i32.const 0)
+ ;; CHECK-NEXT:    (then
+ ;; CHECK-NEXT:     (f64.const 0)
+ ;; CHECK-NEXT:    )
+ ;; CHECK-NEXT:    (else
+ ;; CHECK-NEXT:     (block $block (result f64)
+ ;; CHECK-NEXT:      (nop)
+ ;; CHECK-NEXT:      (br_if $loop
+ ;; CHECK-NEXT:       (i32.eqz
+ ;; CHECK-NEXT:        (i32.const 0)
+ ;; CHECK-NEXT:       )
  ;; CHECK-NEXT:      )
+ ;; CHECK-NEXT:      (unreachable)
  ;; CHECK-NEXT:     )
- ;; CHECK-NEXT:     (unreachable)
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:   )
  ;; CHECK-NEXT:  )
@@ -83,7 +95,9 @@
     )
     (if
      (i32.const 0)
-     (unreachable)
+     (then
+      (unreachable)
+     )
     )
     ;; this will be moved from $block into the if right before it. we must be
     ;; careful to properly finalize() things, as if we finalize the block too
@@ -117,8 +131,12 @@
   ;; LUB
   (if (result funcref)
    (local.get $x)
-   (ref.func $none_=>_i32)
-   (ref.func $i32_=>_none)
+   (then
+    (ref.func $none_=>_i32)
+   )
+   (else
+    (ref.func $i32_=>_none)
+   )
   )
  )