feat: implement scoped type alias (AssemblyScript#2806)

Author: HerrCai0907

Diff for: src/compiler.ts

@@ -93,7 +93,8 @@ import {
   PropertyPrototype,
   IndexSignature,
   File,
-  mangleInternalName
+  mangleInternalName,
+  TypeDefinition
 } from "./program";
 
 import {
@@ -180,7 +181,8 @@ import {
 
   findDecorator,
   isTypeOmitted,
-  Source
+  Source,
+  TypeDeclaration
 } from "./ast";
 
 import {
@@ -1156,7 +1158,7 @@ export class Compiler extends DiagnosticEmitter {
 
       // Resolve type if annotated
       if (typeNode) {
-        let resolvedType = this.resolver.resolveType(typeNode, global.parent); // reports
+        let resolvedType = this.resolver.resolveType(typeNode, null, global.parent); // reports
         if (!resolvedType) {
           global.set(CommonFlags.Errored);
           pendingElements.delete(global);
@@ -2238,13 +2240,7 @@ export class Compiler extends DiagnosticEmitter {
         break;
       }
       case NodeKind.TypeDeclaration: {
-        // TODO: integrate inner type declaration into flow
-        this.error(
-          DiagnosticCode.Not_implemented_0,
-          statement.range,
-          "Inner type alias"
-        );
-        stmt = module.unreachable();
+        stmt = this.compileTypeDeclaration(<TypeDeclaration>statement);
         break;
       }
       case NodeKind.Module: {
@@ -2305,6 +2301,24 @@ export class Compiler extends DiagnosticEmitter {
     return this.module.flatten(stmts);
   }
 
+  private compileTypeDeclaration(statement: TypeDeclaration): ExpressionRef {
+    let flow = this.currentFlow;
+    let name = statement.name.text;
+    let existedTypeAlias = flow.lookupScopedTypeAlias(name);
+    if (existedTypeAlias) {
+      this.errorRelated(
+        DiagnosticCode.Duplicate_identifier_0,
+        statement.range,
+        existedTypeAlias.declaration.range,
+        name
+      );
+      return this.module.unreachable();
+    }
+    let element = new TypeDefinition(name, flow.sourceFunction, statement, DecoratorFlags.None);
+    flow.addScopedTypeAlias(name, element);
+    return this.module.nop();
+  }
+
   private compileBreakStatement(
     statement: BreakStatement
   ): ExpressionRef {
@@ -2962,7 +2976,7 @@ export class Compiler extends DiagnosticEmitter {
       let initializerNode = declaration.initializer;
       if (typeNode) {
         type = resolver.resolveType( // reports
-          typeNode,
+          typeNode, flow,
           flow.sourceFunction,
           cloneMap(flow.contextualTypeArguments)
         );
@@ -3729,7 +3743,7 @@ export class Compiler extends DiagnosticEmitter {
       case AssertionKind.As: {
         let flow = this.currentFlow;
         let toType = this.resolver.resolveType( // reports
-          assert(expression.toType),
+          assert(expression.toType), flow,
           flow.sourceFunction,
           cloneMap(flow.contextualTypeArguments)
         );
@@ -6162,6 +6176,7 @@ export class Compiler extends DiagnosticEmitter {
       typeArguments = this.resolver.resolveTypeArguments(
         assert(typeParameterNodes),
         typeArgumentNodes,
+        this.currentFlow,
         this.currentFlow.sourceFunction.parent,
         cloneMap(this.currentFlow.contextualTypeArguments), // don't update
         expression
@@ -7085,7 +7100,7 @@ export class Compiler extends DiagnosticEmitter {
         let parameterNode = parameterNodes[i];
         if (!isTypeOmitted(parameterNode.type)) {
           let resolvedType = this.resolver.resolveType(
-            parameterNode.type,
+            parameterNode.type, flow,
             sourceFunction.parent,
             contextualTypeArguments
           );
@@ -7105,7 +7120,7 @@ export class Compiler extends DiagnosticEmitter {
       let returnType = contextualSignature.returnType;
       if (!isTypeOmitted(signatureNode.returnType)) {
         let resolvedType = this.resolver.resolveType(
-          signatureNode.returnType,
+          signatureNode.returnType, flow,
           sourceFunction.parent,
           contextualTypeArguments
         );
@@ -7135,7 +7150,7 @@ export class Compiler extends DiagnosticEmitter {
           return module.unreachable();
         }
         let resolvedType = this.resolver.resolveType(
-          thisTypeNode,
+          thisTypeNode, flow,
           sourceFunction.parent,
           contextualTypeArguments
         );
@@ -7522,7 +7537,7 @@ export class Compiler extends DiagnosticEmitter {
     if (isType.kind == NodeKind.NamedType) {
       let namedType = <NamedTypeNode>isType;
       if (!(namedType.isNullable || namedType.hasTypeArguments)) {
-        let element = this.resolver.resolveTypeName(namedType.name, flow.sourceFunction, ReportMode.Swallow);
+        let element = this.resolver.resolveTypeName(namedType.name, flow, flow.sourceFunction, ReportMode.Swallow);
         if (element && element.kind == ElementKind.ClassPrototype) {
           let prototype = <ClassPrototype>element;
           if (prototype.is(CommonFlags.Generic)) {
@@ -7534,7 +7549,7 @@ export class Compiler extends DiagnosticEmitter {
 
     // Fall back to `instanceof TYPE`
     let expectedType = this.resolver.resolveType(
-      expression.isType,
+      expression.isType, flow,
       flow.sourceFunction,
       cloneMap(flow.contextualTypeArguments)
     );
@@ -8686,7 +8701,7 @@ export class Compiler extends DiagnosticEmitter {
     let flow = this.currentFlow;
 
     // obtain the class being instantiated
-    let target = this.resolver.resolveTypeName(expression.typeName, flow.sourceFunction);
+    let target = this.resolver.resolveTypeName(expression.typeName, flow, flow.sourceFunction);
     if (!target) return module.unreachable();
     if (target.kind != ElementKind.ClassPrototype) {
       this.error(
@@ -8722,6 +8737,7 @@ export class Compiler extends DiagnosticEmitter {
       classInstance = this.resolver.resolveClassInclTypeArguments(
         classPrototype,
         typeArguments,
+        flow,
         flow.sourceFunction.parent, // relative to caller
         cloneMap(flow.contextualTypeArguments),
         expression

Diff for: src/flow.ts

@@ -31,7 +31,8 @@ import {
   TypedElement,
   mangleInternalName,
   Property,
-  PropertyPrototype
+  PropertyPrototype,
+  TypeDefinition
 } from "./program";
 
 import {
@@ -250,6 +251,8 @@ export class Flow {
   breakLabel: string | null = null;
   /** Scoped local variables. */
   scopedLocals: Map<string,Local> | null = null;
+  /** Scoped type alias. */
+  scopedTypeAlias: Map<string,TypeDefinition> | null = null;
   /** Local flags. */
   localFlags: LocalFlags[] = [];
   /** Field flags on `this`. Constructors only. */
@@ -405,6 +408,38 @@ export class Flow {
     falseFlows.set(condExpr, falseFlow);
   }
 
+  addScopedTypeAlias(name: string, definition: TypeDefinition): void {
+    let scopedTypeAlias = this.scopedTypeAlias;
+    if (!scopedTypeAlias) this.scopedTypeAlias = scopedTypeAlias = new Map();
+    scopedTypeAlias.set(name, definition);
+  }
+
+  lookupScopedTypeAlias(name: string): TypeDefinition | null {
+    let current: Flow | null = this;
+    do {
+      let scopedTypeAlias = current.scopedTypeAlias;
+      if (scopedTypeAlias && scopedTypeAlias.has(name)) {
+        return assert(scopedTypeAlias.get(name));
+      }
+      current = current.parent;
+    } while (current);
+    return null;
+  }
+
+  lookupTypeAlias(name: string): TypeDefinition | null {
+    let definition: TypeDefinition | null = null;
+    if (definition = this.lookupScopedTypeAlias(name)) return definition;
+
+    let sourceParent = this.sourceFunction.parent;
+    if (sourceParent.kind == ElementKind.Function) {
+      // lookup parent function.
+      let parentFunction = <Function>sourceParent;
+      return parentFunction.flow.lookupTypeAlias(name);
+    }
+    
+    return null;
+  }
+
   /** Gets a free temporary local of the specified type. */
   getTempLocal(type: Type): Local {
     let local = this.targetFunction.addLocal(type);

Diff for: src/program.ts

@@ -1308,7 +1308,7 @@ export class Program extends DiagnosticEmitter {
     for (let i = 0, k = queuedExtends.length; i < k; ++i) {
       let thisPrototype = queuedExtends[i];
       let extendsNode = assert(thisPrototype.extendsNode); // must be present if in queuedExtends
-      let baseElement = resolver.resolveTypeName(extendsNode.name, thisPrototype.parent);
+      let baseElement = resolver.resolveTypeName(extendsNode.name, null, thisPrototype.parent);
       if (!baseElement) continue;
       if (thisPrototype.kind == ElementKind.ClassPrototype) {
         if (baseElement.kind == ElementKind.ClassPrototype) {
@@ -1405,7 +1405,7 @@ export class Program extends DiagnosticEmitter {
       let implementsNodes = assert(thisPrototype.implementsNodes); // must be present if in queuedImplements
       for (let j = 0, l = implementsNodes.length; j < l; ++j) {
         let implementsNode = implementsNodes[j];
-        let interfaceElement = resolver.resolveTypeName(implementsNode.name, thisPrototype.parent);
+        let interfaceElement = resolver.resolveTypeName(implementsNode.name, null, thisPrototype.parent);
         if (!interfaceElement) continue;
         if (interfaceElement.kind == ElementKind.InterfacePrototype) {
           let interfacePrototype = <InterfacePrototype>interfaceElement;
@@ -3383,7 +3383,7 @@ export class TypeDefinition extends TypedElement {
   constructor(
     /** Simple name. */
     name: string,
-    /** Parent element, usually a file or namespace. */
+    /** Parent element. */
     parent: Element,
     /** Declaration reference. */
     declaration: TypeDeclaration,