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

8 files changed, 27 insertions, 15 deletions

diff --git a/test/lit/wasm-split/instrument-funcs.wast b/test/lit/wasm-split/instrument-funcs.wast
index cf3ca4af7..2dbd578f3 100644
--- a/test/lit/wasm-split/instrument-funcs.wast
+++ b/test/lit/wasm-split/instrument-funcs.wast
@@ -36,7 +36,7 @@
 ;; CHECK-NEXT:     (i32.eqz
 ;; CHECK-NEXT:       (global.get $baz_timestamp)
 ;; CHECK-NEXT:     )
-;; CHECK-NEXT:     (block
+;; CHECK-NEXT:     (then
 ;; CHECK-NEXT:       (global.set $monotonic_counter
 ;; CHECK-NEXT:         (i32.add
 ;; CHECK-NEXT:           (global.get $monotonic_counter)
@@ -59,7 +59,7 @@
 ;; CHECK-NEXT:       (local.get $size)
 ;; CHECK-NEXT:       (i32.const 16)
 ;; CHECK-NEXT:     )
-;; CHECK-NEXT:     (block
+;; CHECK-NEXT:     (then
 ;; CHECK-NEXT:       (i64.store align=1
 ;; CHECK-NEXT:         (local.get $addr)
 ;; CHECK-NEXT:         (i64.const {{.*}})
diff --git a/test/lit/wasm-split/instrument-in-memory.wast b/test/lit/wasm-split/instrument-in-memory.wast
index 3208b0b5d..91433d424 100644
--- a/test/lit/wasm-split/instrument-in-memory.wast
+++ b/test/lit/wasm-split/instrument-in-memory.wast
@@ -49,7 +49,7 @@
 ;; CHECK-NEXT:    (local.get $size)
 ;; CHECK-NEXT:    (i32.const 16)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (block
+;; CHECK-NEXT:   (then
 ;; CHECK-NEXT:    (i64.store align=1
 ;; CHECK-NEXT:     (local.get $addr)
 ;; CHECK-NEXT:     (i64.const {{.*}})
diff --git a/test/lit/wasm-split/instrument-in-secondary-memory.wast b/test/lit/wasm-split/instrument-in-secondary-memory.wast
index 26ac0ad18..18a8b0a4f 100644
--- a/test/lit/wasm-split/instrument-in-secondary-memory.wast
+++ b/test/lit/wasm-split/instrument-in-secondary-memory.wast
@@ -52,7 +52,7 @@
 ;; CHECK-NEXT:    (local.get $size)
 ;; CHECK-NEXT:    (i32.const 16)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (block
+;; CHECK-NEXT:   (then
 ;; CHECK-NEXT:    (i64.store $0 align=1
 ;; CHECK-NEXT:     (local.get $addr)
 ;; CHECK-NEXT:     (i64.const {{.*}})
diff --git a/test/lit/wasm-split/instrument-memory64.wast b/test/lit/wasm-split/instrument-memory64.wast
index ff2a56cad..65560d29e 100644
--- a/test/lit/wasm-split/instrument-memory64.wast
+++ b/test/lit/wasm-split/instrument-memory64.wast
@@ -30,7 +30,7 @@
 ;; CHECK-NEXT:    (local.get $size)
 ;; CHECK-NEXT:    (i32.const 16)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (block
+;; CHECK-NEXT:   (then
 ;; CHECK-NEXT:    (i64.store align=1
 ;; CHECK-NEXT:     (local.get $addr)
 ;; CHECK-NEXT:     (i64.const {{.*}})
diff --git a/test/lit/wasm-split/jspi-secondary-export.wast b/test/lit/wasm-split/jspi-secondary-export.wast
index 57fe849a9..3729ec00e 100644
--- a/test/lit/wasm-split/jspi-secondary-export.wast
+++ b/test/lit/wasm-split/jspi-secondary-export.wast
@@ -62,7 +62,9 @@
 ;; PRIMARY-NEXT:   (i32.eqz
 ;; PRIMARY-NEXT:    (global.get $global$1)
 ;; PRIMARY-NEXT:   )
-;; PRIMARY-NEXT:   (call $__load_secondary_module)
+;; PRIMARY-NEXT:   (then
+;; PRIMARY-NEXT:    (call $__load_secondary_module)
+;; PRIMARY-NEXT:   )
 ;; PRIMARY-NEXT:  )
 ;; PRIMARY-NEXT:  (call_indirect (type $0)
 ;; PRIMARY-NEXT:   (local.get $0)
diff --git a/test/lit/wasm-split/jspi.wast b/test/lit/wasm-split/jspi.wast
index 340b2acec..6866f02ff 100644
--- a/test/lit/wasm-split/jspi.wast
+++ b/test/lit/wasm-split/jspi.wast
@@ -43,7 +43,9 @@
  ;; PRIMARY-NEXT:   (i32.eqz
  ;; PRIMARY-NEXT:    (global.get $global$1)
  ;; PRIMARY-NEXT:   )
- ;; PRIMARY-NEXT:   (call $__load_secondary_module)
+ ;; PRIMARY-NEXT:   (then
+ ;; PRIMARY-NEXT:    (call $__load_secondary_module)
+ ;; PRIMARY-NEXT:   )
  ;; PRIMARY-NEXT:  )
  ;; PRIMARY-NEXT:  (call_indirect (type $0)
  ;; PRIMARY-NEXT:   (i32.const 0)
diff --git a/test/lit/wasm-split/multi-memory-lowering-export.wast b/test/lit/wasm-split/multi-memory-lowering-export.wast
index 0721ba2a4..152aaf723 100644
--- a/test/lit/wasm-split/multi-memory-lowering-export.wast
+++ b/test/lit/wasm-split/multi-memory-lowering-export.wast
@@ -55,8 +55,10 @@
 ;; CHECK-NEXT:    )
 ;; CHECK-NEXT:    (i32.const -1)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (return
-;; CHECK-NEXT:    (i32.const -1)
+;; CHECK-NEXT:   (then
+;; CHECK-NEXT:    (return
+;; CHECK-NEXT:     (i32.const -1)
+;; CHECK-NEXT:    )
 ;; CHECK-NEXT:   )
 ;; CHECK-NEXT:  )
 ;; CHECK-NEXT:  (memory.copy
@@ -100,8 +102,10 @@
 ;; CHECK-NEXT:    )
 ;; CHECK-NEXT:    (i32.const -1)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (return
-;; CHECK-NEXT:    (i32.const -1)
+;; CHECK-NEXT:   (then
+;; CHECK-NEXT:    (return
+;; CHECK-NEXT:     (i32.const -1)
+;; CHECK-NEXT:    )
 ;; CHECK-NEXT:   )
 ;; CHECK-NEXT:  )
 ;; CHECK-NEXT:  (local.get $return_size)
diff --git a/test/lit/wasm-split/multi-memory-lowering-import.wast b/test/lit/wasm-split/multi-memory-lowering-import.wast
index d62609108..37ccfa16c 100644
--- a/test/lit/wasm-split/multi-memory-lowering-import.wast
+++ b/test/lit/wasm-split/multi-memory-lowering-import.wast
@@ -52,8 +52,10 @@
 ;; CHECK-NEXT:    )
 ;; CHECK-NEXT:    (i32.const -1)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (return
-;; CHECK-NEXT:    (i32.const -1)
+;; CHECK-NEXT:   (then
+;; CHECK-NEXT:    (return
+;; CHECK-NEXT:     (i32.const -1)
+;; CHECK-NEXT:    )
 ;; CHECK-NEXT:   )
 ;; CHECK-NEXT:  )
 ;; CHECK-NEXT:  (memory.copy
@@ -97,8 +99,10 @@
 ;; CHECK-NEXT:    )
 ;; CHECK-NEXT:    (i32.const -1)
 ;; CHECK-NEXT:   )
-;; CHECK-NEXT:   (return
-;; CHECK-NEXT:    (i32.const -1)
+;; CHECK-NEXT:   (then
+;; CHECK-NEXT:    (return
+;; CHECK-NEXT:     (i32.const -1)
+;; CHECK-NEXT:    )
 ;; CHECK-NEXT:   )
 ;; CHECK-NEXT:  )
 ;; CHECK-NEXT:  (local.get $return_size)