feat: Support rest params in function calls (#2905)

Author: mattjohnsonpint

src/compiler.ts

@@ -182,7 +182,8 @@ import {
   findDecorator,
   isTypeOmitted,
   Source,
-  TypeDeclaration
+  TypeDeclaration,
+  ParameterKind
 } from "./ast";
 
 import {
@@ -6171,16 +6172,7 @@ export class Compiler extends DiagnosticEmitter {
       return false;
     }
 
-    // not yet implemented (TODO: maybe some sort of an unmanaged/lightweight array?)
     let hasRest = signature.hasRest;
-    if (hasRest) {
-      this.error(
-        DiagnosticCode.Not_implemented_0,
-        reportNode.range, "Rest parameters"
-      );
-      return false;
-    }
-
     let minimum = signature.requiredParameters;
     let maximum = signature.parameterTypes.length;
 
@@ -6225,6 +6217,37 @@ export class Compiler extends DiagnosticEmitter {
     }
   }
 
+  private adjustArgumentsForRestParams(
+    argumentExpressions: Expression[],
+    signature: Signature,
+    reportNode: Node
+  ) : Expression[] {
+
+    // if no rest args, return the original args
+    if (!signature.hasRest) {
+      return argumentExpressions;
+    }
+
+    // if there are fewer args than params, then the rest args were not provided
+    // so return the original args
+    const numArguments = argumentExpressions.length;
+    const numParams = signature.parameterTypes.length;
+    if (numArguments < numParams) {
+      return argumentExpressions;
+    }
+      
+    // make an array literal expression from the rest args
+    let elements = argumentExpressions.slice(numParams - 1);
+    let range = new Range(elements[0].range.start, elements[elements.length - 1].range.end);
+    range.source = reportNode.range.source;
+    let arrExpr = new ArrayLiteralExpression(elements, range);
+    
+    // return the original args, but replace the rest args with the array
+    const exprs = argumentExpressions.slice(0, numParams - 1);
+    exprs.push(arrExpr);
+    return exprs;
+  }
+
   /** Compiles a direct call to a concrete function. */
   compileCallDirect(
     instance: Function,
@@ -6246,6 +6269,9 @@ export class Compiler extends DiagnosticEmitter {
     }
     if (instance.hasDecorator(DecoratorFlags.Unsafe)) this.checkUnsafe(reportNode);
 
+    argumentExpressions = this.adjustArgumentsForRestParams(argumentExpressions, signature, reportNode);
+    numArguments = argumentExpressions.length;
+
     // handle call on `this` in constructors
     let sourceFunction = this.currentFlow.sourceFunction;
     if (sourceFunction.is(CommonFlags.Constructor) && reportNode.isAccessOnThis) {
@@ -6477,7 +6503,11 @@ export class Compiler extends DiagnosticEmitter {
       let declaration = originalParameterDeclarations[minArguments + i];
       let initializer = declaration.initializer;
       let initExpr: ExpressionRef;
-      if (initializer) {
+      if (declaration.parameterKind === ParameterKind.Rest) {
+        const arrExpr = new ArrayLiteralExpression([], declaration.range.atEnd);       
+        initExpr = this.compileArrayLiteral(arrExpr, type, Constraints.ConvExplicit);
+        initExpr = module.local_set(operandIndex, initExpr, type.isManaged);        
+      } else if (initializer) {
         initExpr = this.compileExpression(
           initializer,
           type,
@@ -6863,6 +6893,9 @@ export class Compiler extends DiagnosticEmitter {
       return this.module.unreachable();
     }
 
+    argumentExpressions = this.adjustArgumentsForRestParams(argumentExpressions, signature, reportNode);
+    numArguments = argumentExpressions.length;
+
     let numArgumentsInclThis = thisArg ? numArguments + 1 : numArguments;
     let operands = new Array<ExpressionRef>(numArgumentsInclThis);
     let index = 0;

src/resolver.ts

@@ -738,7 +738,9 @@ export class Resolver extends DiagnosticEmitter {
         ctxFlow,
         reportMode,
       );
-      
+      if (!resolvedTypeArguments) {
+        return null;
+      }     
       return this.resolveFunction(
         prototype,
         resolvedTypeArguments,
@@ -778,16 +780,24 @@ export class Resolver extends DiagnosticEmitter {
     let numParameters = parameterNodes.length;
 
     let argumentNodes: Expression[];
+    let argumentsRange: Range;
     switch (node.kind) {
-      case NodeKind.Call:
-        argumentNodes = (<CallExpression>node).args;
+      case NodeKind.Call: {
+        const expr = node as CallExpression;
+        argumentNodes = expr.args;
+        argumentsRange = expr.argumentsRange;
         break;
-      case NodeKind.New: 
-        argumentNodes = (<NewExpression>node).args;
+      }
+      case NodeKind.New: {
+        const expr = node as NewExpression;
+        argumentNodes = expr.args;
+        argumentsRange = expr.argumentsRange;
         break;
-      default:
+      }
+      default: {
         assert(false);
         return null;
+      }
     }
 
     let numArguments = argumentNodes.length;
@@ -802,16 +812,27 @@ export class Resolver extends DiagnosticEmitter {
         if (parameterNodes[i].parameterKind == ParameterKind.Optional) {
           continue;
         }
-        // missing initializer -> too few arguments
         if (reportMode == ReportMode.Report) {
-          this.error(
-            DiagnosticCode.Expected_0_arguments_but_got_1,
-            node.range, numParameters.toString(), numArguments.toString()
-          );
+          if (parameterNodes[i].parameterKind == ParameterKind.Rest) {
+            // rest params are optional, but one element is needed for type inference
+            this.error(
+              DiagnosticCode.Type_argument_expected,
+              argumentsRange.atEnd
+            );
+          } else {
+            // missing initializer -> too few arguments
+            this.error(
+              DiagnosticCode.Expected_0_arguments_but_got_1,
+              node.range, numParameters.toString(), numArguments.toString()
+            );
+          }
         }
         return null;
       }
       let typeNode = parameterNodes[i].type;
+      if (parameterNodes[i].parameterKind == ParameterKind.Rest) {
+        typeNode = (<NamedTypeNode> typeNode).typeArguments![0];
+      }
       if (typeNode.hasGenericComponent(typeParameterNodes)) {
         let type = this.resolveExpression(argumentExpression, ctxFlow, Type.auto, ReportMode.Swallow);
         if (type) {
@@ -2921,10 +2942,13 @@ export class Resolver extends DiagnosticEmitter {
     let numSignatureParameters = signatureParameters.length;
     let parameterTypes = new Array<Type>(numSignatureParameters);
     let requiredParameters = 0;
+    let hasRest = false;
     for (let i = 0; i < numSignatureParameters; ++i) {
       let parameterDeclaration = signatureParameters[i];
       if (parameterDeclaration.parameterKind == ParameterKind.Default) {
         requiredParameters = i + 1;
+      } else if (parameterDeclaration.parameterKind == ParameterKind.Rest) {
+        hasRest = true;
       }
       let typeNode = parameterDeclaration.type;
       if (isTypeOmitted(typeNode)) {
@@ -2984,7 +3008,7 @@ export class Resolver extends DiagnosticEmitter {
       returnType = type;
     }
 
-    let signature = Signature.create(this.program, parameterTypes, returnType, thisType, requiredParameters);
+    let signature = Signature.create(this.program, parameterTypes, returnType, thisType, requiredParameters, hasRest);
 
     let nameInclTypeParameters = prototype.name;
     if (instanceKey.length) nameInclTypeParameters += `<${instanceKey}>`;

tests/compiler/call-rest-err.json

@@ -0,0 +1,14 @@
+{
+  "asc_flags": [
+  ],
+  "stderr": [
+    "TS2322: Type '~lib/string/String' is not assignable to type 'i32'.",
+    "sum('a', 'b')",
+    "TS2322: Type '~lib/string/String' is not assignable to type 'i32'.",
+    "sum('a', 'b')",
+    "TS2322: Type '~lib/string/String' is not assignable to type 'i32'.",
+    "count(1, 'a')",
+    "TS1140: Type argument expected.",
+    "count()"
+  ]
+}

tests/compiler/call-rest-err.ts

@@ -0,0 +1,15 @@
+function sum(...args: i32[]): i32 {
+  let sum = 0;
+  for (let i = 0, k = args.length; i < k; ++i) {
+    sum += args[i];
+  }
+  return sum;
+}
+
+function count<T>(...args: T[]): i32 {
+  return args.length;
+}
+
+sum('a', 'b'); // expect a type mismatch error on each argument
+count(1, 'a'); // expect a type mismatch error on the second argument
+count(); // expect type inference error