Make 'instanceof' behave like TS if the lhs is nullable

src/compiler.ts

@@ -2377,18 +2377,17 @@ export class Compiler extends DiagnosticEmitter {
     }
 
     // any to void
-    if (toType.kind == TypeKind.VOID) {
-      return module.createDrop(expr);
+    if (toType.kind == TypeKind.VOID) return module.createDrop(expr);
+
+    if (!fromType.isAssignableTo(toType)) {
+      if (conversionKind == ConversionKind.IMPLICIT) {
+        this.error(
+          DiagnosticCode.Conversion_from_type_0_to_1_requires_an_explicit_cast,
+          reportNode.range, fromType.toString(), toType.toString()
+        ); // recoverable
+      }
     }
 
-    if (conversionKind == ConversionKind.IMPLICIT && !fromType.isAssignableTo(toType)) {
-      this.error(
-        DiagnosticCode.Conversion_from_type_0_to_1_requires_an_explicit_cast,
-        reportNode.range, fromType.toString(), toType.toString()
-      ); // recoverable
-    }
-
-    // TODO: make this a proper switch?
     if (fromType.is(TypeFlags.FLOAT)) {
 
       // float to float
@@ -4502,7 +4501,7 @@ export class Compiler extends DiagnosticEmitter {
     if (!target) return this.module.createUnreachable();
 
     // to compile just the value, we need to know the target's type
-    var elementType: Type;
+    var targetType: Type;
     switch (target.kind) {
       case ElementKind.GLOBAL: {
         if (!this.compileGlobal(<Global>target)) { // reports; not yet compiled if a static field compiled as a global
@@ -4513,7 +4512,7 @@ export class Compiler extends DiagnosticEmitter {
       }
       case ElementKind.LOCAL:
       case ElementKind.FIELD: {
-        elementType = (<VariableLikeElement>target).type;
+        targetType = (<VariableLikeElement>target).type;
         break;
       }
       case ElementKind.PROPERTY: {
@@ -4522,7 +4521,7 @@ export class Compiler extends DiagnosticEmitter {
           let instance = prototype.resolve(); // reports
           if (!instance) return this.module.createUnreachable();
           assert(instance.signature.parameterTypes.length == 1); // parser must guarantee this
-          elementType = instance.signature.parameterTypes[0];
+          targetType = instance.signature.parameterTypes[0];
           break;
         }
         this.error(
@@ -4551,7 +4550,7 @@ export class Compiler extends DiagnosticEmitter {
             return this.module.createUnreachable();
           }
           assert(indexedSet.signature.parameterTypes.length == 2); // parser must guarantee this
-          elementType = indexedSet.signature.parameterTypes[1];    // 2nd parameter is the element
+          targetType = indexedSet.signature.parameterTypes[1];    // 2nd parameter is the element
           break;
         }
         // fall-through
@@ -4566,7 +4565,7 @@ export class Compiler extends DiagnosticEmitter {
     }
 
     // compile the value and do the assignment
-    var valueExpr = this.compileExpression(valueExpression, elementType, ConversionKind.IMPLICIT, WrapMode.NONE);
+    var valueExpr = this.compileExpression(valueExpression, targetType, ConversionKind.IMPLICIT, WrapMode.NONE);
     return this.compileAssignmentWithValue(
       expression,
       valueExpr,
@@ -5882,12 +5881,26 @@ export class Compiler extends DiagnosticEmitter {
     expression: InstanceOfExpression,
     contextualType: Type
   ): ExpressionRef {
-    this.compileExpressionRetainType(expression.expression, this.options.usizeType, WrapMode.NONE);
+    var module = this.module;
+    // NOTE that this differs from TypeScript in that the rhs is a type, not an expression. at the
+    // time of implementation, this seemed more useful because dynamic rhs expressions are not
+    // possible in AS anyway.
+    var expr = this.compileExpressionRetainType(expression.expression, this.options.usizeType, WrapMode.NONE);
     var type = this.currentType;
     var isType = this.program.resolveType(expression.isType);
     this.currentType = Type.bool;
-    if (!isType) return this.module.createUnreachable();
-    return this.module.createI32(type.isAssignableTo(isType, false) ? 1 : 0);
+    if (!isType) return module.createUnreachable();
+    return type.is(TypeFlags.NULLABLE) && !isType.is(TypeFlags.NULLABLE)
+      ? type.nonNullableType.isAssignableTo(isType)
+        ? module.createBinary( // not precomputeable
+            type.is(TypeFlags.LONG)
+              ? BinaryOp.NeI64
+              : BinaryOp.NeI32,
+            expr,
+            type.toNativeZero(module)
+          )
+        : module.createI32(0)
+      : module.createI32(type.isAssignableTo(isType, true) ? 1 : 0);
   }
 
   compileLiteralExpression(

src/program.ts

@@ -1847,7 +1847,9 @@ export class Program extends DiagnosticEmitter {
     if (node.kind == NodeKind.SIGNATURE) {
       let signature = this.resolveSignature(<SignatureNode>node, contextualTypeArguments, reportNotFound);
       if (!signature) return null;
-      return Type.u32.asFunction(signature);
+      return node.isNullable
+        ? signature.type.asNullable()
+        : signature.type;
     }
     var typeNode = <TypeNode>node;
     var simpleName = typeNode.name.text;
@@ -1867,7 +1869,10 @@ export class Program extends DiagnosticEmitter {
             contextualTypeArguments,
             null
           ); // reports
-          return instance ? instance.type : null;
+          if (!instance) return null;
+          return node.isNullable
+            ? instance.type.asNullable()
+            : instance.type;
         }
       }
     }

src/types.ts

@@ -170,6 +170,7 @@ export class Type {
     if (!this.cachedNullableType) {
       assert(!this.is(TypeFlags.NULLABLE));
       this.cachedNullableType = new Type(this.kind, this.flags | TypeFlags.NULLABLE, this.size);
+      this.cachedNullableType.nonNullableType = this;
       this.cachedNullableType.classReference = this.classReference;       // either a class reference
       this.cachedNullableType.signatureReference = this.signatureReference; // or a function reference
     }
@@ -177,27 +178,29 @@ export class Type {
   }
 
   /** Tests if a value of this type is assignable to a target of the specified type. */
-  isAssignableTo(target: Type, signednessIsImportant: bool = false): bool {
+  isAssignableTo(target: Type, signednessIsRelevant: bool = false): bool {
     var currentClass: Class | null;
     var targetClass: Class | null;
     var currentFunction: Signature | null;
     var targetFunction: Signature | null;
     if (this.is(TypeFlags.REFERENCE)) {
       if (target.is(TypeFlags.REFERENCE)) {
-        if (currentClass = this.classReference) {
-          if (targetClass = target.classReference) {
-            return currentClass.isAssignableTo(targetClass);
-          }
-        } else if (currentFunction = this.signatureReference) {
-          if (targetFunction = target.signatureReference) {
-            return currentFunction.isAssignableTo(targetFunction);
+        if (!this.is(TypeFlags.NULLABLE) || target.is(TypeFlags.NULLABLE)) {
+          if (currentClass = this.classReference) {
+            if (targetClass = target.classReference) {
+              return currentClass.isAssignableTo(targetClass);
+            }
+          } else if (currentFunction = this.signatureReference) {
+            if (targetFunction = target.signatureReference) {
+              return currentFunction.isAssignableTo(targetFunction);
+            }
           }
         }
       }
     } else if (!target.is(TypeFlags.REFERENCE)) {
       if (this.is(TypeFlags.INTEGER)) {
         if (target.is(TypeFlags.INTEGER)) {
-          if (!signednessIsImportant || this.is(TypeFlags.SIGNED) == target.is(TypeFlags.SIGNED)) {
+          if (!signednessIsRelevant || this.is(TypeFlags.SIGNED) == target.is(TypeFlags.SIGNED)) {
             return this.size <= target.size;
           }
         } else if (target.kind == TypeKind.F32) {
@@ -223,6 +226,21 @@ export class Type {
 
   /** Converts this type to its TypeScript representation. */
   toString(kindOnly: bool = false): string {
+    if (!kindOnly && this.is(TypeFlags.REFERENCE)) {
+      let classReference = this.classReference;
+      if (classReference) {
+        return this.is(TypeFlags.NULLABLE)
+          ? classReference.toString() + " | null"
+          : classReference.toString();
+      }
+      let signatureReference = this.signatureReference;
+      if (signatureReference) {
+        return this.is(TypeFlags.NULLABLE)
+          ? "(" + signatureReference.toString(true) + ") | null"
+          : signatureReference.toString(true);
+      }
+      assert(false);
+    }
     switch (this.kind) {
       case TypeKind.I8: return "i8";
       case TypeKind.I16: return "i16";
@@ -231,23 +249,14 @@ export class Type {
       case TypeKind.ISIZE: return "isize";
       case TypeKind.U8: return "u8";
       case TypeKind.U16: return "u16";
-      case TypeKind.U32: {
-        let functionType = this.signatureReference;
-        return kindOnly || !functionType ? "u32" : functionType.toString(true);
-      }
+      case TypeKind.U32: return "u32";
       case TypeKind.U64: return "u64";
-      case TypeKind.USIZE: {
-        let classType = this.classReference;
-        return kindOnly || !classType ? "usize" : classType.toString();
-      }
+      case TypeKind.USIZE: return "usize";
       case TypeKind.BOOL: return "bool";
       case TypeKind.F32: return "f32";
       case TypeKind.F64: return "f64";
+      default: assert(false);
       case TypeKind.VOID: return "void";
-      default: {
-        assert(false);
-        return "";
-      }
     }
   }
 

tests/compiler/instanceof.optimized.wat

@@ -4,6 +4,7 @@
  (type $Fi (func (param f64) (result i32)))
  (type $v (func))
  (import "env" "abort" (func $~lib/env/abort (param i32 i32 i32 i32)))
+ (global $instanceof/an (mut i32) (i32.const 0))
  (memory $0 1)
  (data (i32.const 8) "\0d\00\00\00i\00n\00s\00t\00a\00n\00c\00e\00o\00f\00.\00t\00s")
  (export "memory" (memory $0))
@@ -14,7 +15,10 @@
  (func $instanceof/isI32<f64> (; 2 ;) (type $Fi) (param $0 f64) (result i32)
   (i32.const 0)
  )
- (func $start (; 3 ;) (type $v)
+ (func $instanceof/isI32<u32> (; 3 ;) (type $ii) (param $0 i32) (result i32)
+  (i32.const 0)
+ )
+ (func $start (; 4 ;) (type $v)
   (if
    (i32.eqz
     (call $instanceof/isI32<i32>
@@ -45,5 +49,48 @@
     (unreachable)
    )
   )
+  (if
+   (call $instanceof/isI32<u32>
+    (i32.const 0)
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 40)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (get_global $instanceof/an)
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 43)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (set_global $instanceof/an
+   (i32.const 1)
+  )
+  (if
+   (i32.eqz
+    (get_global $instanceof/an)
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 46)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
  )
 )

tests/compiler/instanceof.ts

@@ -37,13 +37,14 @@ function isI32<T>(v: T): bool {
 
 assert( isI32(0));
 assert(!isI32(0.0));
+assert(!isI32(<u32>0)); // signedness is relevant
 
-// TODO: what about nullables?
-// var an: A | null;
-// var bn: B | null;
-//
-// assert(an instanceof A);
-// assert(bn instanceof A);
-//
-// assert(!(an instanceof B));
-// assert(bn instanceof B);
+var an: A | null = null;
+assert(!(an instanceof A));       // TS: null is not an instance of A
+assert(  an instanceof A | null); // AS: null is     an instance of A | null
+an = changetype<A | null>(1);
+assert(  an instanceof A);        // TS: non-null is an instance of A
+assert(  an instanceof A | null); // AS: non-null is an instance of A | null
+
+// TODO: keep track of nullability during flows, so this becomes precomputable:
+// assert(an !== null && an instanceof A);

tests/compiler/instanceof.untouched.wat

@@ -8,6 +8,7 @@
  (global $instanceof/b (mut i32) (i32.const 0))
  (global $instanceof/i (mut i32) (i32.const 0))
  (global $instanceof/f (mut f32) (f32.const 0))
+ (global $instanceof/an (mut i32) (i32.const 0))
  (global $HEAP_BASE i32 (i32.const 40))
  (memory $0 1)
  (data (i32.const 8) "\0d\00\00\00i\00n\00s\00t\00a\00n\00c\00e\00o\00f\00.\00t\00s\00")
@@ -23,7 +24,12 @@
    (i32.const 0)
   )
  )
- (func $start (; 3 ;) (type $v)
+ (func $instanceof/isI32<u32> (; 3 ;) (type $ii) (param $0 i32) (result i32)
+  (return
+   (i32.const 0)
+  )
+ )
+ (func $start (; 4 ;) (type $v)
   (if
    (i32.eqz
     (i32.const 1)
@@ -304,5 +310,90 @@
     (unreachable)
    )
   )
+  (if
+   (i32.eqz
+    (i32.eqz
+     (call $instanceof/isI32<u32>
+      (i32.const 0)
+     )
+    )
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 40)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (i32.eqz
+    (i32.eqz
+     (i32.ne
+      (get_global $instanceof/an)
+      (i32.const 0)
+     )
+    )
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 43)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (i32.eqz
+    (i32.const 1)
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 44)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (set_global $instanceof/an
+   (i32.const 1)
+  )
+  (if
+   (i32.eqz
+    (i32.ne
+     (get_global $instanceof/an)
+     (i32.const 0)
+    )
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 46)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (i32.eqz
+    (i32.const 1)
+   )
+   (block
+    (call $~lib/env/abort
+     (i32.const 0)
+     (i32.const 8)
+     (i32.const 47)
+     (i32.const 0)
+    )
+    (unreachable)
+   )
+  )
  )
 )