Add a flag to opt in to the old WAT parser

src/tools/wasm-opt.cpp

@@ -220,6 +220,13 @@ int main(int argc, const char* argv[]) {
          [&outputSourceMapUrl](Options* o, const std::string& argument) {
            outputSourceMapUrl = argument;
          })
+    .add(
+      "--deprecated-wat-parser",
+      "",
+      "Use the old, deprecated WAT parser. This option will be removed soon!",
+      WasmOptOption,
+      Options::Arguments::Zero,
+      [](Options*, const std::string&) { useNewWATParser = false; })
     .add("--new-wat-parser",
          "",
          "Use the experimental new WAT parser",

test/lit/deprecated-wat.wast

@@ -0,0 +1,24 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+
+;; RUN: wasm-opt --deprecated-wat-parser -all %s -S -o - | filecheck %s
+
+(module
+ ;; CHECK:      (type $0 (func (param i32)))
+
+ ;; CHECK:      (type $1 (func (result i32)))
+
+ ;; CHECK:      (import "env" "bad" (func $wrong (type $0) (param i32)))
+
+ ;; CHECK:      (func $foo (type $1) (result i32)
+ ;; CHECK-NEXT:  (i32.const 0)
+ ;; CHECK-NEXT: )
+ (func $foo (result i32)
+  ;; Non-standard block result format
+  (block i32
+   (i32.const 0)
+  )
+ )
+
+ ;; Non-standard import after declared function
+ (import $wrong "env" "bad" (param i32))
+)

test/lit/help/wasm-opt.test

@@ -72,6 +72,10 @@
 ;; CHECK-NEXT:   --output-source-map-url,-osu                  Emit specified string as source
 ;; CHECK-NEXT:                                                 map URL
 ;; CHECK-NEXT:
+;; CHECK-NEXT:   --deprecated-wat-parser                       Use the old, deprecated WAT
+;; CHECK-NEXT:                                                 parser. This option will be
+;; CHECK-NEXT:                                                 removed soon!
+;; CHECK-NEXT:
 ;; CHECK-NEXT:   --new-wat-parser                              Use the experimental new WAT
 ;; CHECK-NEXT:                                                 parser
 ;; CHECK-NEXT: