Generates the Scala.js IR for a compilation unit This method iterates over all the class and interface definitions found in the compilation unit and emits their IR (.sjsir).

Some classes are never actually emitted:

• Classes representing primitive types
• The scala.Array class
• Implementation classes for JS traits

Some classes representing anonymous functions are not actually emitted. Instead, a temporary representation of their apply method is built and recorded, so that it can be inlined as a JavaScript anonymous function in the method that instantiates it.

Other ClassDefs are emitted according to their nature: * Non-native JS class -> genNonNativeJSClass() * Other JS type (<: js.Any) -> genJSClassData() * Interface -> genInterface() * Normal class -> genClass()

Ensures that the value of the given tree is boxed.

Ensures that the value of the given tree is boxed when used as a method result value.

Extracts a value typed as Any to the given type after posterasure.

Generate an instance of an anonymous (non-lambda) JS class inline

Gen JS code for an Apply node (method call)

There's a whole bunch of varieties of Apply nodes: regular method calls, super calls, constructor calls, isInstanceOf/asInstanceOf, primitives, JS calls, etc. They are further dispatched in here.

Gen definitions for the fields of a class. The fields are initialized with the zero of their types.

Gen JS code for a JS function class.

This is called when emitting a ClassDef that represents an anonymous class extending js.FunctionN. These are generated by the SAM synthesizer when the target type is a js.FunctionN. Since JS functions are not classes, we deconstruct the ClassDef, then reconstruct it to be a genuine Closure.

Compared to tryGenAnonFunctionClass(), this function must always succeed, because we really cannot afford keeping them as anonymous classes. The good news is that it can do so, because the body of SAM lambdas is hoisted in the enclosing class. Hence, the apply() method is just a forwarder to calling that hoisted method.

From a class looking like this:

final class <anon>(outer, capture1, ..., captureM) extends js.FunctionN[...] { def apply(param1, ..., paramN) = { outer.lambdaImpl(param1, ..., paramN, capture1, ..., captureM) } } new <anon>(o, c1, ..., cM)

we generate a function:

lambda<o, c1, ..., cM>[notype]( outer, capture1, ..., captureM, param1, ..., paramN) { outer.lambdaImpl(param1, ..., paramN, capture1, ..., captureM) }

Gen JS code for LabelDef.

If a LabelDef reaches this method, then the only valid jumps are from within it, which means it basically represents a loop. Other kinds of LabelDefs, notably those for matches, are caught upstream and transformed in ad hoc ways.

The general transformation for

labelName(...labelParams) {
  rhs
}: T

is the following:

block[T]: {
  while (true) {
    labelName[void]: {
      return@block transformedRhs
    }
  }
}

where all jumps to the label inside the rhs of the form

labelName(...args)

are transformed into

...labelParams = ...args;
return@labelName (void 0)

This is always correct, so it can handle arbitrary labels and jumps such as those produced by loops, tail-recursive calls and even some compiler plugins (see for example #1148). However, the result is unnecessarily ugly for simple while and do while loops, so we have some post-processing to simplify those.

Generate loading of a module value.

Can be given either the module symbol or its module class symbol.

If the module we load refers to the global scope (i.e., it is annotated with @JSGlobalScope), report a compile error specifying that a global scope object should only be used as the qualifier of a .-selection.

Generate loading of a module value or the global scope.

Can be given either the module symbol of its module class symbol.

Unlike genLoadModule, this method does not fail if the module we load refers to the global scope.

Gen JS code for a Match, i.e., a switch-able pattern match.

In most cases, this straightforwardly translates to a Match in the IR, which will eventually become a switch in JavaScript.

However, sometimes there is a guard in here, despite the fact that matches cannot have guards (in the JVM nor in the IR). The JVM backend emits a jump to the default clause when a guard is not fulfilled. We cannot do that, since we do not have arbitrary jumps. We therefore use a funny encoding with two nested Labeled blocks. For example,

x match {
  case 1 if y > 0 => a
  case 2          => b
  case _          => c
}

arrives at the back-end as

x match {
  case 1 =>
    if (y > 0)
      a
    else
      default()
  case 2 =>
    b
  case _ =>
    default() {
      c
    }
}

which we then translate into the following IR:

matchResult[I]: {
  default[V]: {
    x match {
      case 1 =>
        return(matchResult) if (y > 0)
          a
        else
          return(default) (void 0)
      case 2 =>
        return(matchResult) b
      case _ =>
        ()
    }
  }
  c
}

Generates exported methods and properties for a class.

Maybe gen JS code for a method definition.

Some methods are not emitted at all:

• Primitives, since they are never actually called (with exceptions)
• Abstract methods in non-native JS classes
• Default accessor of a native JS constructor
• Constructors of hijacked classes

Generates the MethodDef of a (non-constructor) method

Most normal methods are emitted straightforwardly. If the result type is Unit, then the body is emitted as a statement. Otherwise, it is emitted as an expression.

The additional complexity of this method handles the transformation of a peculiarity of recursive tail calls: the local ValDef that replaces this.

Gen JS code for a method definition in a class or in an impl class. On the JS side, method names are mangled to encode the full signature of the Scala method, as described in JSEncoding, to support overloading.

Constructors are emitted by generating their body as a statement.

Other (normal) methods are emitted with genMethodDef().

Gen JS code for a Labeled block from a pattern match'es match-end, while trying to optimize it away as an If chain.

It is important to do so at compile-time because, when successful, the resulting IR can be much better optimized by the optimizer.

The optimizer also does something similar, but *after* it has processed the body of the Labeled block, at which point it has already lost any information about stack-allocated values.

!!! There is quite of bit of code duplication with OptimizerCore.tryOptimizePatternMatch.

Generates a Scala argument from dispatched JavaScript arguments (unboxing and default parameter handling).

Gen JS code for a tree in statement or expression position (in the IR).

This is the main transformation method. Each node of the Scala AST is transformed into an equivalent portion of the JS AST.

Gen the static forwarders to the members of a class or interface for methods of its companion object.

This is only done if there exists a companion object and it is not a JS type.

Precondition: isCandidateForForwarders(sym) is true

Gen the static forwarders for the methods of a module class.

Precondition: isCandidateForForwarders(moduleClass) is true

Gen JS code for a try..catch or try..finally block

try..finally blocks are compiled straightforwardly to try..finally blocks of JS.

try..catch blocks are a bit more subtle, as JS does not have type-based selection of exceptions to catch. We thus encode explicitly the type tests, like in:

try { ... } catch (e) { if (e.isInstanceOf[IOException]) { ... } else if (e.isInstanceOf[Exception]) { ... } else { throw e; // default, re-throw } }