Backport V1 Typed function type syntax to v0 (#1623)

Author: markwpearce

src/files/BrsFile.spec.ts

@@ -4583,6 +4583,20 @@ describe('BrsFile', () => {
                 `);
             });
         });
+
+        describe('typed functions in type expressions', () => {
+            it('transpiles to function', () => {
+                testTranspile(`
+                    function test(func as function(name as string, num as integer) as integer) as integer
+                        return func("hello", 123)
+                    end function
+                `, `
+                    function test(func as Function) as integer
+                        return func("hello", 123)
+                    end function
+                `);
+            });
+        });
     });
 
     it('allows up to 63 function params', () => {

src/parser/Parser.spec.ts

@@ -1785,6 +1785,108 @@ describe('parser', () => {
             expectZeroDiagnostics(diagnostics);
         });
     });
+
+    describe('typed functions as types', () => {
+        it('disallowed in brightscript mode', () => {
+            let { diagnostics } = parse(`
+                function test(func as function())
+                    return func()
+                end function
+             `, ParseMode.BrightScript);
+            expectDiagnosticsIncludes(diagnostics, [
+                DiagnosticMessages.unexpectedToken(')')
+            ]);
+        });
+
+        it('can be passed as param types', () => {
+            let { diagnostics } = parse(`
+                function test(func as function())
+                    return func()
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can have a return type', () => {
+            let { diagnostics } = parse(`
+                function test(func as sub() as integer) as integer
+                    return func()
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can use sub or function', () => {
+            let { diagnostics } = parse(`
+                function test(func as sub() as integer) as integer
+                    return func()
+                end function
+
+                function test2(func as function() as integer) as integer
+                    return func()
+                 end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can have primitive parameters', () => {
+            let { diagnostics } = parse(`
+                function test(func as function(name as string, num as integer) as integer) as integer
+                    return func("hello", 123)
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can have complex parameters', () => {
+            let { diagnostics } = parse(`
+                interface IFace
+                    name as string
+                end interface
+
+                function test(func as function(thing as IFace) as integer) as integer
+                    return func({name: "hello"})
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can have compound parameters', () => {
+            let { diagnostics } = parse(`
+                interface IFace
+                    name as string
+                end interface
+
+                function test(func as function(arg1 as string or integer, arg2 as IFace) as integer) as integer
+                    return func("hello", {name: "hello"})
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can be used as return types', () => {
+            let { diagnostics } = parse(`
+                function test() as function() as integer
+                    return function() as integer
+                        return 123
+                    end function
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+
+        it('can have a union as return type', () => {
+            let { diagnostics } = parse(`
+                type foo = function() as integer or string
+                function test() as foo
+                    return function() as integer
+                        return 123
+                    end function
+                end function
+             `, ParseMode.BrighterScript);
+            expectZeroDiagnostics(diagnostics);
+        });
+    });
 });
 
 function parse(text: string, mode?: ParseMode) {

src/parser/Parser.ts

@@ -2813,7 +2813,9 @@ export class Parser {
         while (lookForCompounds) {
             lookForCompounds = false;
 
-            if (this.checkAny(...DeclarableTypes)) {
+            const isTypedFunction = this.checkAny(TokenKind.Function, TokenKind.Sub) && this.checkNext(TokenKind.LeftParen);
+
+            if (this.checkAny(...DeclarableTypes) && !isTypedFunction) {
                 // Token is a built in type
                 typeToken = this.advance();
             } else if (this.options.mode === ParseMode.BrighterScript) {
@@ -2824,6 +2826,9 @@ export class Parser {
                     } else if (this.check(TokenKind.LeftParen)) {
                         // could be an inline interface
                         typeToken = this.groupedTypeExpression();
+                    } else if (isTypedFunction) {
+                        //typed function type
+                        typeToken = this.typedFunctionType();
                     } else {
                         // see if we can get a namespaced identifer
                         const qualifiedType = this.getNamespacedVariableNameExpression(ignoreDiagnostics);
@@ -2941,6 +2946,28 @@ export class Parser {
         return createToken(TokenKind.Dynamic, null, util.createBoundingRange(leftParen, typeToken, rightParen));
     }
 
+    private typedFunctionType() {
+        const funcOrSub = this.advance();
+        const leftParen = this.advance();
+
+        let params = [] as FunctionParameterExpression[];
+        if (!this.check(TokenKind.RightParen)) {
+            do {
+                params.push(this.functionParameter());
+            } while (this.match(TokenKind.Comma));
+        }
+        const rightParen = this.advance();
+        let asToken: Token;
+        let returnType: Token;
+        if ((this.check(TokenKind.As))) {
+            // this is a function type with a return type, e.g. `function(string) as void`
+            asToken = this.advance();
+            returnType = this.typeToken();
+        }
+
+        return createToken(TokenKind.Function, null, util.createBoundingRange(funcOrSub, leftParen, rightParen, asToken, returnType));
+    }
+
     private primary(): Expression {
         switch (true) {
             case this.matchAny(