feat: Add nonnull/NonNullable builtin type (#1875)

Author: Willem Wyndham

src/common.ts

@@ -147,6 +147,7 @@ export namespace CommonNames {
   export const indexof = "indexof";
   export const valueof = "valueof";
   export const returnof = "returnof";
+  export const nonnull = "nonnull";
   // aliases
   export const null_ = "null";
   export const true_ = "true";

src/program.ts

@@ -992,6 +992,12 @@ export class Program extends DiagnosticEmitter {
       this.makeNativeTypeDeclaration(CommonNames.returnof, CommonFlags.EXPORT | CommonFlags.GENERIC),
       DecoratorFlags.BUILTIN
     ));
+    this.nativeFile.add(CommonNames.nonnull, new TypeDefinition(
+      CommonNames.nonnull,
+      this.nativeFile,
+      this.makeNativeTypeDeclaration(CommonNames.nonnull, CommonFlags.EXPORT | CommonFlags.GENERIC),
+      DecoratorFlags.BUILTIN
+    ));
 
     // The following types might not be enabled by compiler options, so the
     // compiler needs to check this condition whenever such a value is created

src/resolver.ts

@@ -296,6 +296,7 @@ export class Resolver extends DiagnosticEmitter {
         if (text == CommonNames.indexof) return this.resolveBuiltinIndexofType(node, ctxElement, ctxTypes, reportMode);
         if (text == CommonNames.valueof) return this.resolveBuiltinValueofType(node, ctxElement, ctxTypes, reportMode);
         if (text == CommonNames.returnof) return this.resolveBuiltinReturnTypeType(node, ctxElement, ctxTypes, reportMode);
+        if (text == CommonNames.nonnull) return this.resolveBuiltinNotNullableType(node, ctxElement, ctxTypes, reportMode);
       }
 
       // Resolve normally
@@ -438,19 +439,9 @@ export class Resolver extends DiagnosticEmitter {
     /** How to proceed with eventual diagnostics. */
     reportMode: ReportMode = ReportMode.REPORT
   ): Type | null {
-    var typeArgumentNodes = node.typeArguments;
-    if (!typeArgumentNodes || typeArgumentNodes.length != 1) {
-      if (reportMode == ReportMode.REPORT) {
-        let numTypeArguments = 0;
-        if (typeArgumentNodes) numTypeArguments = typeArgumentNodes.length;
-        this.error(
-          DiagnosticCode.Expected_0_type_arguments_but_got_1,
-          node.range, "1", numTypeArguments.toString()
-        );
-      }
-      return null;
-    }
-    var typeArgument = this.resolveType(typeArgumentNodes[0], ctxElement, ctxTypes, reportMode);
+    const typeArgumentNode = this.ensureOneTypeArgument(node, reportMode);
+    if (!typeArgumentNode) return null;
+    var typeArgument = this.resolveType(typeArgumentNode, ctxElement, ctxTypes, reportMode);
     if (!typeArgument) return null;
     switch (typeArgument.kind) {
       case TypeKind.I8:
@@ -483,26 +474,16 @@ export class Resolver extends DiagnosticEmitter {
     /** How to proceed with eventual diagnostics. */
     reportMode: ReportMode = ReportMode.REPORT
   ): Type | null {
-    var typeArgumentNodes = node.typeArguments;
-    if (!typeArgumentNodes || typeArgumentNodes.length != 1) {
-      if (reportMode == ReportMode.REPORT) {
-        let numTypeArguments = 0;
-        if (typeArgumentNodes) numTypeArguments = typeArgumentNodes.length;
-        this.error(
-          DiagnosticCode.Expected_0_type_arguments_but_got_1,
-          node.range, "1", numTypeArguments.toString()
-        );
-      }
-      return null;
-    }
-    var typeArgument = this.resolveType(typeArgumentNodes[0], ctxElement, ctxTypes, reportMode);
+    const typeArgumentNode = this.ensureOneTypeArgument(node, reportMode);
+    if (!typeArgumentNode) return null;
+    var typeArgument = this.resolveType(typeArgumentNode, ctxElement, ctxTypes, reportMode);
     if (!typeArgument) return null;
     var classReference = typeArgument.classReference;
     if (!classReference) {
       if (reportMode == ReportMode.REPORT) {
         this.error(
           DiagnosticCode.Index_signature_is_missing_in_type_0,
-          typeArgumentNodes[0].range, typeArgument.toString()
+          typeArgumentNode.range, typeArgument.toString()
         );
       }
       return null;
@@ -520,7 +501,7 @@ export class Resolver extends DiagnosticEmitter {
     if (reportMode == ReportMode.REPORT) {
       this.error(
         DiagnosticCode.Index_signature_is_missing_in_type_0,
-        typeArgumentNodes[0].range, typeArgument.toString()
+        typeArgumentNode.range, typeArgument.toString()
       );
     }
     return null;
@@ -536,19 +517,9 @@ export class Resolver extends DiagnosticEmitter {
     /** How to proceed with eventual diagnostics. */
     reportMode: ReportMode = ReportMode.REPORT
   ): Type | null {
-    var typeArgumentNodes = node.typeArguments;
-    if (!typeArgumentNodes || typeArgumentNodes.length != 1) {
-      let numTypeArguments = 0;
-      if (typeArgumentNodes) numTypeArguments = typeArgumentNodes.length;
-      if (reportMode == ReportMode.REPORT) {
-        this.error(
-          DiagnosticCode.Expected_0_type_arguments_but_got_1,
-          node.range, "1", numTypeArguments.toString()
-        );
-      }
-      return null;
-    }
-    var typeArgument = this.resolveType(typeArgumentNodes[0], ctxElement, ctxTypes, reportMode);
+    const typeArgumentNode = this.ensureOneTypeArgument(node, reportMode);
+    if (!typeArgumentNode) return null;
+    var typeArgument = this.resolveType(typeArgumentNode, ctxElement, ctxTypes, reportMode);
     if (!typeArgument) return null;
     var classReference = typeArgument.getClassOrWrapper(this.program);
     if (classReference) {
@@ -558,7 +529,7 @@ export class Resolver extends DiagnosticEmitter {
     if (reportMode == ReportMode.REPORT) {
       this.error(
         DiagnosticCode.Index_signature_is_missing_in_type_0,
-        typeArgumentNodes[0].range, typeArgument.toString()
+        typeArgumentNode.range, typeArgument.toString()
       );
     }
     return null;
@@ -574,31 +545,39 @@ export class Resolver extends DiagnosticEmitter {
     /** How to proceed with eventualy diagnostics. */
     reportMode: ReportMode = ReportMode.REPORT
   ): Type | null {
-    var typeArgumentNodes = node.typeArguments;
-    if (!typeArgumentNodes || typeArgumentNodes.length != 1) {
-      if (reportMode == ReportMode.REPORT) {
-        let numTypeArguments = 0;
-        if (typeArgumentNodes) numTypeArguments = typeArgumentNodes.length;
-        this.error(
-          DiagnosticCode.Expected_0_type_arguments_but_got_1,
-          node.range, "1", numTypeArguments.toString()
-        );
-      }
-      return null;
-    }
-    var typeArgument = this.resolveType(typeArgumentNodes[0], ctxElement, ctxTypes, reportMode);
+    const typeArgumentNode = this.ensureOneTypeArgument(node, reportMode);
+    if (!typeArgumentNode) return null;
+    var typeArgument = this.resolveType(typeArgumentNode, ctxElement, ctxTypes, reportMode);
     if (!typeArgument) return null;
     var signatureReference = typeArgument.getSignature();
     if (signatureReference) return signatureReference.returnType;
     if (reportMode == ReportMode.REPORT) {
       this.error(
         DiagnosticCode.Type_0_has_no_call_signatures,
-        typeArgumentNodes[0].range, typeArgument.toString()
+        typeArgumentNode.range, typeArgument.toString()
       );
     }
     return null;
   }
 
+  private resolveBuiltinNotNullableType(
+    /** The type to resolve. */
+    node: NamedTypeNode,
+    /** Contextual element. */
+    ctxElement: Element,
+    /** Contextual types, i.e. `T`. */
+    ctxTypes: Map<string,Type> | null = null,
+    /** How to proceed with eventual diagnostics. */
+    reportMode: ReportMode = ReportMode.REPORT
+  ): Type | null {
+    const typeArgumentNode = this.ensureOneTypeArgument(node, reportMode);
+    if (!typeArgumentNode) return null;
+    var typeArgument = this.resolveType(typeArgumentNode, ctxElement, ctxTypes, reportMode);
+    if (!typeArgument) return null;
+    if (!typeArgument.isNullableReference) return typeArgument;
+    return typeArgument.nonNullableType;
+  }
+
   /** Resolves a type name to the program element it refers to. */
   resolveTypeName(
     /** The type name to resolve. */
@@ -3362,4 +3341,24 @@ export class Resolver extends DiagnosticEmitter {
     }
     return instance;
   }
+
+  private ensureOneTypeArgument(
+    /** The type to resolve. */
+    node: NamedTypeNode,
+    /** How to proceed with eventual diagnostics. */
+    reportMode: ReportMode = ReportMode.REPORT
+  ): TypeNode | null {
+    var typeArgumentNodes = node.typeArguments;
+    let numTypeArguments = 0;
+    if (!typeArgumentNodes || (numTypeArguments = typeArgumentNodes.length) != 1) {
+      if (reportMode == ReportMode.REPORT) {
+        this.error(
+          DiagnosticCode.Expected_0_type_arguments_but_got_1,
+          node.range, "1", numTypeArguments.toString()
+        );
+      }
+      return null;
+    }
+    return typeArgumentNodes[0];
+  }
 }

std/assembly/compat.ts

@@ -1 +1,2 @@
 export type ReturnType<T> = returnof<T>;
+export type NonNullable<T> = nonnull<T>;

std/assembly/index.d.ts

@@ -1314,6 +1314,10 @@ declare type valueof<T extends unknown[]> = T[0];
 declare type ReturnType<T extends (...args: any) => any> = T extends (...args: any) => infer R ? R : any;
 /** A special type evaluated to the return type of T if T is a callable function. */
 declare type returnof<T extends (...args: any) => any> = ReturnType<T>;
+/** A special type that excludes null and undefined from T. */
+declare type NonNullable<T> = T extends null | undefined ? never : T;
+/** A special type that excludes null and undefined from T. */
+declare type nonnull<T> = NonNullable<T>;
 
 /** Pseudo-class representing the backing class of integer types. */
 declare class _Integer {

tests/asconfig/complicated/asconfig.json

@@ -14,4 +14,4 @@
     "initialMemory": 100,
     "enable": ["simd"]
   }
-}
+}

tests/asconfig/extends/expected.json

@@ -5,4 +5,4 @@
     "noAssert": true,
     "enable": ["simd"]
   }
-}
+}

tests/asconfig/target/expected.json

@@ -3,4 +3,4 @@
     "exportRuntime": false,
     "noAssert": true
   }
-}
+}