Support sequences of sequences in generated bindings.

unroll recursively gets the inner type of any sequence type encountered, so it's inappropriate for codegen that only wants the immediate inner type. However, if a type identifies as a sequence and is nullable, we need to reach through the nullable wrapper first. Gecko does very similar things.

components/script/dom/bindings/codegen/CodegenRust.py

@@ -87,6 +87,11 @@ def stripTrailingWhitespace(text):
     return '\n'.join(lines) + tail
 
 
+def innerSequenceType(type):
+    assert type.isSequence()
+    return type.inner.inner if type.nullable() else type.inner
+
+
 def MakeNativeName(name):
     return name[0].upper() + name[1:]
 
@@ -713,7 +718,7 @@ def wrapObjectTemplate(templateBody, nullValue, isDefinitelyObject, type,
         raise TypeError("Can't handle array arguments yet")
 
     if type.isSequence():
-        innerInfo = getJSToNativeConversionInfo(type.unroll(), descriptorProvider)
+        innerInfo = getJSToNativeConversionInfo(innerSequenceType(type), descriptorProvider)
         declType = CGWrapper(innerInfo.declType, pre="Vec<", post=">")
         config = getConversionConfigForType(type, isEnforceRange, isClamp, treatNullAs)
 
@@ -1302,8 +1307,7 @@ def getRetvalDeclarationForType(returnType, descriptorProvider):
     if returnType.isObject() or returnType.isSpiderMonkeyInterface():
         return CGGeneric("*mut JSObject")
     if returnType.isSequence():
-        inner = returnType.unroll()
-        result = getRetvalDeclarationForType(inner, descriptorProvider)
+        result = getRetvalDeclarationForType(innerSequenceType(returnType), descriptorProvider)
         result = CGWrapper(result, pre="Vec<", post=">")
         if returnType.nullable():
             result = CGWrapper(result, pre="Option<", post=">")
@@ -3743,7 +3747,7 @@ def getUnionTypeTemplateVars(type, descriptorProvider):
         typeName = name
     elif type.isSequence():
         name = type.name
-        inner = getUnionTypeTemplateVars(type.unroll(), descriptorProvider)
+        inner = getUnionTypeTemplateVars(innerSequenceType(type), descriptorProvider)
         typeName = "Vec<" + inner["typeName"] + ">"
     elif type.isArray():
         name = str(type)

components/script/dom/testbinding.rs

@@ -9,7 +9,7 @@ use dom::bindings::codegen::Bindings::FunctionBinding::Function;
 use dom::bindings::codegen::Bindings::TestBindingBinding;
 use dom::bindings::codegen::Bindings::TestBindingBinding::{TestBindingMethods, TestDictionary};
 use dom::bindings::codegen::Bindings::TestBindingBinding::{TestDictionaryDefaults, TestEnum};
-use dom::bindings::codegen::UnionTypes::{BlobOrBoolean, BlobOrBlobSequence};
+use dom::bindings::codegen::UnionTypes::{BlobOrBoolean, BlobOrBlobSequence, LongOrLongSequenceSequence};
 use dom::bindings::codegen::UnionTypes::{BlobOrString, BlobOrUnsignedLong, EventOrString};
 use dom::bindings::codegen::UnionTypes::{EventOrUSVString, HTMLElementOrLong};
 use dom::bindings::codegen::UnionTypes::{HTMLElementOrUnsignedLongOrStringOrBoolean, LongSequenceOrBoolean};
@@ -572,6 +572,17 @@ impl TestBindingMethods for TestBinding {
     fn FuncControlledMethodDisabled(&self) {}
     fn FuncControlledMethodEnabled(&self) {}
 
+    fn PassSequenceSequence(&self, _seq: Vec<Vec<i32>>) {}
+    fn ReturnSequenceSequence(&self) -> Vec<Vec<i32>> { vec![] }
+    fn PassUnionSequenceSequence(&self, seq: LongOrLongSequenceSequence) {
+        match seq {
+            LongOrLongSequenceSequence::Long(_) => (),
+            LongOrLongSequenceSequence::LongSequenceSequence(seq) => {
+                let _seq: Vec<Vec<i32>> = seq;
+            }
+        }
+    }
+
     #[allow(unsafe_code)]
     fn CrashHard(&self) {
         static READ_ONLY_VALUE: i32 = 0;

components/script/dom/webidls/TestBinding.webidl

@@ -409,6 +409,10 @@ interface TestBinding {
   void passVariadicAny(any... args);
   void passVariadicObject(object... args);
 
+  void passSequenceSequence(sequence<sequence<long>> seq);
+  sequence<sequence<long>> returnSequenceSequence();
+  void passUnionSequenceSequence((long or sequence<sequence<long>>) seq);
+
   static attribute boolean booleanAttributeStatic;
   static void receiveVoidStatic();
   boolean BooleanMozPreference(DOMString pref_name);