Merge pull request #5 from jow-/new-type-system

New type system

22 files changed, 1464 insertions, 0 deletions

diff --git a/tests/custom/00_syntax/00_single_line_comments b/tests/custom/00_syntax/00_single_line_comments
new file mode 100644
index 0000000..24a32a2
--- /dev/null
+++ b/tests/custom/00_syntax/00_single_line_comments
@@ -0,0 +1,15 @@
+Single line comments.
+
+-- Expect stdout --
+This is  a test.
+ a test.
+A test .
+
+-- End --
+
+-- Testcase --
+This is {# a comment within #} a test.
+{# Comment before #} a test.
+A test {# and a comment after #}.
+{# This is a comment with embedded "{#" tag. #}
+-- End --
diff --git a/tests/custom/00_syntax/01_unterminated_comment b/tests/custom/00_syntax/01_unterminated_comment
new file mode 100644
index 0000000..1d3669c
--- /dev/null
+++ b/tests/custom/00_syntax/01_unterminated_comment
@@ -0,0 +1,15 @@
+Unterminated comment
+
+-- Expect stderr --
+Syntax error: Unterminated template block
+In line 1, byte 9:
+
+ `This is {# an unclosed comment`
+          ^-- Near here
+
+
+-- End --
+
+-- Testcase --
+This is {# an unclosed comment
+-- End --
diff --git a/tests/custom/00_syntax/02_multi_line_comments b/tests/custom/00_syntax/02_multi_line_comments
new file mode 100644
index 0000000..99fc37e
--- /dev/null
+++ b/tests/custom/00_syntax/02_multi_line_comments
@@ -0,0 +1,12 @@
+Multiline comments.
+
+-- Expect stdout --
+This is an example text  for testing comment blocks.
+-- End --
+
+-- Testcase --
+This is an example text {# containing
+a comment spanning multiple lines and
+	different indentation
+		#} for testing comment blocks.
+-- End --
diff --git a/tests/custom/00_syntax/03_expression_blocks b/tests/custom/00_syntax/03_expression_blocks
new file mode 100644
index 0000000..3568016
--- /dev/null
+++ b/tests/custom/00_syntax/03_expression_blocks
@@ -0,0 +1,11 @@
+Testing expression blocks.
+
+-- Expect stdout --
+The result of 3 * 7 is 21.
+To escape the start tag, output it as string expression: {{
+-- End --
+
+-- Testcase --
+The result of 3 * 7 is {{ 3 * 7 }}.
+To escape the start tag, output it as string expression: {{ "{{" }}
+-- End --
diff --git a/tests/custom/00_syntax/04_statement_blocks b/tests/custom/00_syntax/04_statement_blocks
new file mode 100644
index 0000000..920ed71
--- /dev/null
+++ b/tests/custom/00_syntax/04_statement_blocks
@@ -0,0 +1,20 @@
+Testing statement blocks.
+
+-- Expect stdout --
+The result of 3 * 7 is 21.
+A statement block may contain multiple statements: Hello World
+To escape the start tag, output it as string expression: {%
+Alternatively print it: {%
+-- End --
+
+-- Testcase --
+The result of 3 * 7 is {%+ print(3 * 7) %}.
+A statement block may contain multiple statements: {%+
+	print("Hello ");
+	print("World");
+%}
+
+To escape the start tag, output it as string expression: {{ "{%" }}
+Alternatively print it: {%+ print("{%") %}
+
+-- End --
diff --git a/tests/custom/00_syntax/05_block_nesting b/tests/custom/00_syntax/05_block_nesting
new file mode 100644
index 0000000..fcfd7da
--- /dev/null
+++ b/tests/custom/00_syntax/05_block_nesting
@@ -0,0 +1,24 @@
+Nesting blocks into non-comment blocks should fail.
+
+-- Expect stderr --
+Syntax error: Template blocks may not be nested
+In line 2, byte 61:
+
+ `We may not nest statement blocks into expression blocks: {{ {% print(1 + 2) %} }}.`
+  Near here --------------------------------------------------^
+
+
+Syntax error: Template blocks may not be nested
+In line 3, byte 61:
+
+ `We may not nest expression blocks into statement blocks: {% {{ 1 + 2 }} %}.`
+  Near here --------------------------------------------------^
+
+
+-- End --
+
+-- Testcase --
+We can nest other block types into comments: {# {% {{ 1 + 2 }} %} #}
+We may not nest statement blocks into expression blocks: {{ {% print(1 + 2) %} }}.
+We may not nest expression blocks into statement blocks: {% {{ 1 + 2 }} %}.
+-- End --
diff --git a/tests/custom/00_syntax/06_open_statement_block b/tests/custom/00_syntax/06_open_statement_block
new file mode 100644
index 0000000..9c2d142
--- /dev/null
+++ b/tests/custom/00_syntax/06_open_statement_block
@@ -0,0 +1,13 @@
+The last statement block of a template may remain open, this is useful for templates
+that contain only code.
+
+-- Expect stdout --
+This template consists entirely of script code!
+-- End --
+
+-- Testcase --
+{%
+	print("This template ");
+	print("consists entirely ");
+	print("of script code!\n");
+-- End --
diff --git a/tests/custom/00_syntax/07_embedded_single_line_comments b/tests/custom/00_syntax/07_embedded_single_line_comments
new file mode 100644
index 0000000..43f188c
--- /dev/null
+++ b/tests/custom/00_syntax/07_embedded_single_line_comments
@@ -0,0 +1,21 @@
+Statement and expression blocks may contain C++-style comments.
+A C++-style comment is started by two subsequent slashes and spans
+until the next newline.
+
+-- Expect stdout --
+The result of 5 + 9 is 14.
+Statement blocks may use C++ comments too: Test Another test.
+-- End --
+
+-- Testcase --
+The result of 5 + 9 is {{ // The block end tag is ignored: }}
+// And the expression block continues here!
+5 + 9 }}.
+Statement blocks may use C++ comments too: {%+
+	print("Test"); // A comment.
+
+	// Another comment.
+	print(" Another test.");
+%}
+
+-- End --
diff --git a/tests/custom/00_syntax/08_embedded_multi_line_comments b/tests/custom/00_syntax/08_embedded_multi_line_comments
new file mode 100644
index 0000000..75aba5f
--- /dev/null
+++ b/tests/custom/00_syntax/08_embedded_multi_line_comments
@@ -0,0 +1,24 @@
+Statement and expression blocks may contain C-style comments.
+A C-style comment is started by a slash followed by an asterisk
+and ended by an asterisk followed by a slash.
+
+Such comments may appear everywhere within statement or expression
+blocks, even in the middle of statements or expressions.
+
+-- Expect stdout --
+The result of 12 - 4 is 8.
+Statement blocks may use C comments too: Test Another test. The final test.
+-- End --
+
+-- Testcase --
+The result of 12 - 4 is {{ /* A comment before */ 12 - /* or even within */ 4 /* or after an expression */ }}.
+Statement blocks may use C comments too: {%+
+	print("Test"); /* A comment. */
+
+	/* Another comment. */
+	print(" Another test.");
+
+	print(/* A comment within */ " The final test.");
+%}
+
+-- End --
diff --git a/tests/custom/00_syntax/09_string_literals b/tests/custom/00_syntax/09_string_literals
new file mode 100644
index 0000000..0967850
--- /dev/null
+++ b/tests/custom/00_syntax/09_string_literals
@@ -0,0 +1,50 @@
+String literals may be enclosed in single or double quotes.
+Embedded escape sequences are started with a backslash, followed
+by either a hexadecimal, an octal or a single character escape sequence.
+
+-- Expect stdout --
+Single quoted string
+Double quoted string
+Unicode escape sequence: ☀💩
+Escaped double quote (") character
+Escaped single quote (') character
+Hexadecimal escape: XYZ xyz
+Octal escape: ABC xyz
+{ "Single char escape": "\u0007\b\u001b\f\r\t\u000b\\\n" }
+-- End --
+
+-- Testcase --
+{{ 'Single quoted string' }}
+{{ "Double quoted string" }}
+{{ "Unicode escape sequence: \u2600\uD83D\uDCA9" }}
+{{ "Escaped double quote (\") character" }}
+{{ 'Escaped single quote (\') character' }}
+{{ "Hexadecimal escape: \x58\x59\x5A \x78\x79\x7a" }}
+{{ "Octal escape: \101\102\103 \170\171\172" }}
+{{ { "Single char escape": "\a\b\e\f\r\t\v\\\n" } }}
+-- End --
+
+
+Testing various parsing corner cases.
+
+-- Expect stdout --
+[ "\t", "\n", "y", "\u0001", "\n", "\u0001\u0002", "\u0001\u0002", "\u0001\u0002", "\u0001a", "\na" ]
+-- End --
+
+-- Testcase --
+{%
+	print([
+		"\	",  	// properly handle escaped tab
+		"\
+",  				// properly handle escaped newline
+		"\y",		// substitute unrecognized escape with escaped char
+		"\1",		// handle short octal sequence at end of string
+		"\12",		// handle short octal sequence at end of string
+		"\1\2",		// handle subsequent short octal sequences
+		"\001\2",	// handle short sequence after long one
+		"\1\002",	// handle long sequence after short one
+		"\1a",		// handle short octal sequence terminated by non-octal char
+		"\12a"		// handle short octal sequence terminated by non-octal char
+	], "\n");
+%}
+-- End --
diff --git a/tests/custom/00_syntax/10_numeric_literals b/tests/custom/00_syntax/10_numeric_literals
new file mode 100644
index 0000000..3e367d0
--- /dev/null
+++ b/tests/custom/00_syntax/10_numeric_literals
@@ -0,0 +1,26 @@
+C-style numeric integer and float literals are understood, as well
+as the special keywords "Infinity" and "NaN" to denote the IEEE 754
+floating point values.
+
+Numeric values are either stored as signed 64 bit integers or signed
+doubles internally.
+
+-- Expect stdout --
+Integers literals: 123, 127, 2748, 57082
+Float literals: 10, 10.3, 1.23456e-65, 16.0625
+Special values: Infinity, Infinity, NaN, NaN
+Minimum values: -9223372036854775808, -1.79769e+308
+Maximum values: 9223372036854775807, 1.79769e+308
+Minimum truncation: -9223372036854775808, -Infinity
+Maximum truncation: 9223372036854775807, Infinity
+-- End --
+
+-- Testcase --
+Integers literals: {{ 123 }}, {{ 0177 }}, {{ 0xabc }}, {{ 0xDEFA }}
+Float literals: {{ 10. }}, {{ 10.3 }}, {{ 123.456e-67 }}, {{ 0x10.1 }}
+Special values: {{ Infinity }}, {{ 1 / 0 }}, {{ NaN }}, {{ "x" / 1 }}
+Minimum values: {{ -9223372036854775808 }}, {{ -1.7976931348623158e+308 }}
+Maximum values: {{ 9223372036854775807 }}, {{ 1.7976931348623158e+308 }}
+Minimum truncation: {{ -10000000000000000000 }}, {{ -1.0e309 }}
+Maximum truncation: {{ 10000000000000000000 }}, {{ 1.0e309 }}
+-- End --
diff --git a/tests/custom/00_syntax/11_misc_literals b/tests/custom/00_syntax/11_misc_literals
new file mode 100644
index 0000000..372741c
--- /dev/null
+++ b/tests/custom/00_syntax/11_misc_literals
@@ -0,0 +1,17 @@
+The utpl script language features a number of keywords which represent
+certain special values.
+
+-- Expect stdout --
+The "this" keyword refers to the current function context: object
+The "null" keyword represents the null value: null
+The "true" keyword represents a true boolean value: true
+The "false" keyword represents a false boolean value: false
+-- End --
+
+-- Testcase --
+{% let t = { f: function() { return this; } } %}
+The "this" keyword refers to the current function context: {{ type(t.f()) }}
+The "null" keyword represents the null value: {{ "" + null }}
+The "true" keyword represents a true boolean value: {{ true }}
+The "false" keyword represents a false boolean value: {{ false }}
+-- End --
diff --git a/tests/custom/00_syntax/12_block_whitespace_control b/tests/custom/00_syntax/12_block_whitespace_control
new file mode 100644
index 0000000..911171c
--- /dev/null
+++ b/tests/custom/00_syntax/12_block_whitespace_control
@@ -0,0 +1,47 @@
+By default, whitespace before a block start tag or after a block end tag
+is retained. By suffixing the start tag or prefixing the end tag with a
+dash, the leading or trailing whitespace is trimmed respectively.
+
+-- Expect stdout --
+Whitespace control applies to all block types:
+Comment before: | |, after: | |, both: ||
+Statement before: |test |, after: | test|, both: |test|
+Expression before: |test |, after: | test|, both: |test|
+
+By default whitespace around a block is retained.
+Leading whitespace can be trimmed like this.
+The same applies to trailing whitespace.
+It is also possible to trim bothleading and trailingwhitespace.
+
+Stripping works across multiple lines as well:test
+
+Likewise, stripping over multiple lines of trailing whitespace works as
+expected too.This is after the block.
+-- End --
+
+-- Testcase --
+Whitespace control applies to all block types:
+Comment before: | {#- test #} |, after: | {#- test #} |, both: | {#- test -#} |
+Statement before: | {%- print("test") %} |, after: | {%+ print("test") -%} |, both: | {%- print("test") -%} |
+Expression before: | {{- "test" }} |, after: | {{ "test" -}} |, both: | {{- "test" -}} |
+
+By default whitespace {{ "around a block" }} is retained.
+Leading whitespace can be trimmed {#- note the leading dash #} like this.
+The same applies to {# note the trailing dash -#} trailing whitespace.
+It is also possible to trim both {{- "leading and trailing" -}} whitespace.
+
+Stripping works across multiple lines as well:
+
+{%-
+    /* The word "test" will be printed after "well:" above */
+    print("test")
+%}
+
+
+Likewise, stripping over multiple lines of trailing whitespace works as
+expected too.
+
+{#- Any whitespace after "expected too." and before "This is after the block" will be trimmed. -#}
+
+This is after the block.
+-- End --
diff --git a/tests/custom/00_syntax/13_object_literals b/tests/custom/00_syntax/13_object_literals
new file mode 100644
index 0000000..18fbbed
--- /dev/null
+++ b/tests/custom/00_syntax/13_object_literals
@@ -0,0 +1,174 @@
+The utpl script language supports declaring objects (dictionaries) using
+either JSON or JavaScript notation.
+
+-- Expect stdout --
+{ }
+{ "name": "Bob", "age": 31, "email": { "work": "bob@example.com", "private": "bob@example.org" } }
+{ "banana": "yellow", "tomato": "red", "broccoli": "green" }
+{ "foo": "bar", "complex key": "qrx" }
+{ "foo": { "bar": true } }
+-- End --
+
+-- Testcase --
+{%
+	// An empty object can be declared using a pair of curly brackets
+	empty_obj = { };
+
+	// It is also possible to use JSON notation to declare an object
+	json_obj = {
+		"name": "Bob",
+		"age": 31,
+		"email": {
+			"work": "bob@example.com",
+			"private": "bob@example.org"
+		}
+	};
+
+	// Declaring an object in JavaScript notation is supported as well
+	another_obj = {
+		banana: "yellow",
+		tomato: "red",
+		broccoli: "green"
+	};
+
+	// Mixing styles is allowed too
+	third_obj = {
+		foo: "bar",
+		"complex key": "qrx"
+	};
+
+	// Important caveat: when nesting objects, ensure that curly brackets
+	// are separated by space or newline to avoid interpretation as
+	// expression block tag!
+	nested_obj = { foo: { bar: true } }; // <-- mind the space in "} }"
+
+	// Printing (or stringifying) objects will return their JSON representation
+	print(empty_obj, "\n");
+	print(json_obj, "\n");
+	print(another_obj, "\n");
+	print(third_obj, "\n");
+	print(nested_obj, "\n");
+%}
+-- End --
+
+
+Additionally, utpl implements ES6-like spread operators to allow shallow copying
+of object properties into other objects.
+
+-- Expect stdout --
+{ "foo": true, "bar": false }
+{ "foo": true, "bar": false, "baz": 123, "qrx": 456 }
+{ "foo": false, "bar": true, "baz": 123, "qrx": 456 }
+{ "foo": true, "bar": false }
+{ "foo": true, "bar": false, "level2": { "baz": 123, "qrx": 456 } }
+{ "foo": true, "bar": false, "0": 7, "1": 8, "2": 9 }
+-- End --
+
+-- Testcase --
+{%
+	o1 = { foo: true, bar: false };
+	o2 = { baz: 123, qrx: 456 };
+	arr = [7, 8, 9];
+
+	print(join("\n", [
+		// copying one object into another
+		{ ...o1 },
+
+		// combining two objects
+		{ ...o1, ...o2 },
+
+		// copying object and override properties
+		{ ...o1, ...o2, foo: false, bar: true },
+
+		// default properties overwritten by spread operator
+		{ foo: 123, bar: 456, ...o1 },
+
+		// nested spread operators
+		{ ...o1, level2: { ...o2 } },
+
+		// merging array into objects
+		{ ...o1, ...arr }
+	]), "\n");
+%}
+-- End --
+
+
+ES2015 short hand property notation is supported as well.
+
+-- Expect stdout --
+{ "a": 123, "b": true, "c": "test" }
+-- End --
+
+-- Testcase --
+{%
+	a = 123;
+	b = true;
+	c = "test";
+
+	o = { a, b, c };
+
+	print(o, "\n");
+%}
+-- End --
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ':'
+In line 2, byte 14:
+
+ `    o = { "foo" };`
+  Near here ------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	o = { "foo" };
+%}
+-- End --
+
+
+ES2015 computed property names are supported.
+
+-- Expect stdout --
+{ "test": true, "hello": false, "ABC": 123 }
+-- End --
+
+-- Testcase --
+{%
+	s = "test";
+	o = {
+		[s]: true,
+		["he" + "llo"]: false,
+		[uc("abc")]: 123
+	};
+
+	print(o, "\n");
+%}
+-- End --
+
+-- Expect stderr --
+Syntax error: Expecting expression
+In line 2, byte 10:
+
+ `    o1 = { []: true };`
+  Near here --^
+
+
+Syntax error: Unexpected token
+Expecting ']'
+In line 3, byte 14:
+
+ `    o2 = { [true, false]: 123 };`
+  Near here ------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	o1 = { []: true };
+	o2 = { [true, false]: 123 };
+%}
+-- End --
diff --git a/tests/custom/00_syntax/14_array_literals b/tests/custom/00_syntax/14_array_literals
new file mode 100644
index 0000000..941ee4a
--- /dev/null
+++ b/tests/custom/00_syntax/14_array_literals
@@ -0,0 +1,82 @@
+The utpl script language supports declaring arrays using JSON notation.
+
+-- Expect stdout --
+[ ]
+[ "first", "second", 123, [ "a", "nested", "array" ], { "a": "nested object" } ]
+-- End --
+
+-- Testcase --
+{%
+	// An empty array can be declared using a pair of square brackets
+	empty_array = [ ];
+
+	// JSON notation is used to declare an array with contents
+	json_array = [
+		"first",
+		"second",
+		123,
+		[ "a", "nested", "array" ],
+		{ a: "nested object" }
+	];
+
+	// Printing (or stringifying) arrays will return their JSON representation
+	print(empty_array, "\n");
+	print(json_array, "\n");
+-- End --
+
+
+Additionally, utpl implements ES6-like spread operators to allow shallow copying
+of array values into other arrays.
+
+-- Expect stdout --
+[ 1, 2, 3 ]
+[ 1, 2, 3, 4, 5, 6 ]
+[ 1, 2, 3, 4, 5, 6, false, true ]
+[ 1, 2, 3, false, true, 4, 5, 6 ]
+[ 1, 2, 3, [ 4, 5, 6 ] ]
+-- End --
+
+-- Testcase --
+{%
+	a1 = [ 1, 2, 3 ];
+	a2 = [ 4, 5, 6 ];
+
+	print(join("\n", [
+		// copying one array into another
+		[ ...a1 ],
+
+		// combining two arrays
+		[ ...a1, ...a2 ],
+
+		// copying array and append values
+		[ ...a1, ...a2, false, true ],
+
+		// copy array and interleave values
+		[ ...a1, false, true, ...a2 ],
+
+		// nested spread operators
+		[ ...a1, [ ...a2 ] ]
+	]), "\n");
+%}
+-- End --
+
+Contrary to merging arrays into objects, objects cannot be merged into arrays.
+
+-- Expect stderr --
+Type error: ({ "foo": true, "bar": false }) is not iterable
+In line 5, byte 21:
+
+ `    print([ ...arr, ...obj ], "\n");`
+  Near here -------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	arr = [ 1, 2, 3 ];
+	obj = { foo: true, bar: false };
+
+	print([ ...arr, ...obj ], "\n");
+%}
+-- End --
diff --git a/tests/custom/00_syntax/15_function_declarations b/tests/custom/00_syntax/15_function_declarations
new file mode 100644
index 0000000..4257dd6
--- /dev/null
+++ b/tests/custom/00_syntax/15_function_declarations
@@ -0,0 +1,164 @@
+Function declarations follow the ECMAScript 5 syntax. Functions can be
+declared anonymously, which is useful for "throw-away" functions such
+as sort or filter callbacks or for building objects or arrays of function
+values.
+
+If functions are declared with a name, the resulting function value is
+automatically assigned under the given name to the current scope.
+
+When function values are stringifed, the resulting string will describe
+the declaration of the function.
+
+Nesting function declarations is possible as well.
+
+
+-- Expect stdout --
+function() { ... }
+function test_fn(a, b) { ... }
+function test2_fn(a, b) { ... }
+
+A function declaration using the alternative syntax:
+The function was called with arguments 123 and 456.
+
+-- End --
+
+-- Testcase --
+{%
+	// declare an anonymous function and
+	// assign resulting value
+	anon_fn = function() {
+		return "test";
+	};
+
+	// declare a named function
+	function test_fn(a, b) {
+		return a + b;
+	}
+
+	// nesting functions is legal
+	function test2_fn(a, b) {
+		function test3_fn(a, b) {
+			return a * b;
+		}
+
+		return a + test3_fn(a, b);
+	}
+
+	print(anon_fn, "\n");
+	print(test_fn, "\n");
+	print(test2_fn, "\n");
+%}
+
+A function declaration using the alternative syntax:
+{% function test3_fn(a, b): %}
+The function was called with arguments {{ a }} and {{ b }}.
+{% endfunction %}
+{{ test3_fn(123, 456) }}
+-- End --
+
+
+Additionally, utpl implements ES6-like "rest" argument syntax to declare
+variadic functions.
+
+-- Expect stdout --
+function non_variadic(a, b, c, d, e) { ... }
+[ 1, 2, 3, 4, 5 ]
+function variadic_1(a, b, ...args) { ... }
+[ 1, 2, [ 3, 4, 5 ] ]
+function variadic_2(...args) { ... }
+[ [ 1, 2, 3, 4, 5 ] ]
+-- End --
+
+-- Testcase --
+{%
+	// ordinary, non-variadic function
+	function non_variadic(a, b, c, d, e) {
+		return [ a, b, c, d, e ];
+	}
+
+	// fixed amount of arguments with variable remainder
+	function variadic_1(a, b, ...args) {
+		return [ a, b, args ];
+	}
+
+	// only variable arguments
+	function variadic_2(...args) {
+		return [ args ];
+	}
+
+	print(join("\n", [
+		non_variadic,
+		non_variadic(1, 2, 3, 4, 5),
+		variadic_1,
+		variadic_1(1, 2, 3, 4, 5),
+		variadic_2,
+		variadic_2(1, 2, 3, 4, 5)
+	]), "\n");
+%}
+-- End --
+
+
+Complementary to the "rest" argument syntax, the spread operator may be
+used in function call arguments to pass arrays of values as argument list.
+
+-- Expect stdout --
+[ 1, 2, 3, 4, 5, 6 ]
+[ 4, 5, 6, 1, 2, 3 ]
+[ 1, 2, 3, 1, 2, 3 ]
+[ 1, 2, 3 ]
+-- End --
+
+-- Testcase --
+{%
+	arr = [ 1, 2, 3 ];
+
+	function test(...args) {
+		return args;
+	}
+
+	print(join("\n", [
+		test(...arr, 4, 5, 6),
+		test(4, 5, 6, ...arr),
+		test(...arr, ...arr),
+		test(...arr)
+	]), "\n");
+%}
+-- End --
+
+
+Rest arguments may be only used once in a declaration and they must always
+be the last item in the argument list.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ')'
+In line 2, byte 26:
+
+ `    function illegal(...args, ...args2) {}`
+  Near here ------------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	function illegal(...args, ...args2) {}
+%}
+-- End --
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ')'
+In line 2, byte 26:
+
+ `    function illegal(...args, a, b) {}`
+  Near here ------------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	function illegal(...args, a, b) {}
+%}
+-- End --
diff --git a/tests/custom/00_syntax/16_for_loop b/tests/custom/00_syntax/16_for_loop
new file mode 100644
index 0000000..67edc21
--- /dev/null
+++ b/tests/custom/00_syntax/16_for_loop
@@ -0,0 +1,299 @@
+Two for-loop variants are supported: a C-style counting for loop
+consisting of an initialization expression, a test condition
+and a step expression and a for-in-loop variant which allows
+enumerating properties of objects or items of arrays.
+
+Additionally, utpl supports an alternative syntax suitable for
+template block tags.
+
+
+-- Expect stdout --
+A simple counting for-loop:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+Any of the init-, test- and increment expressions may be omitted.
+
+Loop without initialization statement:
+Iteration null
+Iteration 1
+Iteration 2
+
+Loop without test statement:
+Iteration 0
+Iteration 1
+Iteration 2
+
+Loop without init-, test- or increment statement:
+Iteration 1
+Iteration 2
+Iteration 3
+
+For-in loop enumerating object properties:
+Key: foo
+Key: bar
+
+For-in loop enumerating array items:
+Item: one
+Item: two
+Item: three
+
+A counting for-loop using the alternative syntax:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+A for-in loop using the alternative syntax:
+Item 123
+Item 456
+Item 789
+
+For-in and counting for loops may declare variables:
+Iteration 0
+Iteration 1
+Iteration 2
+
+Item 123
+Item 456
+Item 789
+-- End --
+
+-- Testcase --
+A simple counting for-loop:
+{%
+	for (i = 0; i < 10; i++) {
+		print("Iteration ");
+		print(i);
+		print("\n");
+	}
+%}
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+{%
+ 	for (i = 0; i < 10; i++)
+		print("Iteration ", i, "\n");
+%}
+
+Any of the init-, test- and increment expressions may be omitted.
+
+Loop without initialization statement:
+{%
+	for (; j < 3; j++)
+		print("Iteration " + j + "\n");
+%}
+
+Loop without test statement:
+{%
+	for (j = 0;; j++) {
+		if (j == 3)
+			break;
+
+		print("Iteration ", j, "\n");
+	}
+%}
+
+Loop without init-, test- or increment statement:
+{%
+	for (;;) {
+		if (k++ == 3)
+			break;
+
+		print("Iteration ", k, "\n");
+	}
+%}
+
+For-in loop enumerating object properties:
+{%
+	obj = { foo: true, bar: false };
+	for (key in obj)
+		print("Key: ", key, "\n");
+%}
+
+For-in loop enumerating array items:
+{%
+	arr = [ "one", "two", "three" ];
+	for (item in arr)
+		print("Item: ", item, "\n");
+%}
+
+A counting for-loop using the alternative syntax:
+{% for (x = 0; x < 10; x++): -%}
+Iteration {{ x }}
+{% endfor %}
+
+A for-in loop using the alternative syntax:
+{% for (n in [123, 456, 789]): -%}
+Item {{ n }}
+{% endfor %}
+
+For-in and counting for loops may declare variables:
+{% for (let i = 0; i < 3; i++): %}
+Iteration {{ i }}
+{% endfor %}
+
+{% for (let n in [123, 456, 789]): %}
+Item {{ n }}
+{% endfor %}
+-- End --
+
+
+By specifying two loop variables in for-in loop expressions, keys
+and values can be iterated simultaneously.
+
+-- Expect stdout --
+true
+false
+123
+456
+[ 0, true ]
+[ 1, false ]
+[ 2, 123 ]
+[ 3, 456 ]
+foo
+bar
+baz
+qrx
+[ "foo", true ]
+[ "bar", false ]
+[ "baz", 123 ]
+[ "qrx", 456 ]
+-- End --
+
+-- Testcase --
+{%
+	let arr = [ true, false, 123, 456 ];
+	let obj = { foo: true, bar: false, baz: 123, qrx: 456 };
+
+	// iterating arrays with one loop variable yields the array values
+	for (let x in arr)
+		print(x, "\n");
+
+	// iterating arrays with two loop variables yields the array indexes
+	// and their corresponding values
+	for (let x, y in arr)
+		print([x, y], "\n");
+
+	// iterating objects with one loop variable yields the object keys
+	for (let x in obj)
+		print(x, "\n");
+
+	// iterating objects with two loop variables yields the object keys
+	// and their corresponding values
+	for (let x, y in obj)
+		print([x, y], "\n");
+%}
+-- End --
+
+
+Ensure that for-in loop expressions with more than two variables are
+rejected.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 24:
+
+ `    for (let x, y, z in {})`
+  Near here ----------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x, y, z in {})
+		;
+%}
+-- End --
+
+
+Ensure that assignments in for-in loop expressions are rejected.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 25:
+
+ `    for (let x = 1, y in {})`
+  Near here -----------------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x = 1, y in {})
+		;
+%}
+-- End --
+
+
+Ensure that too short for-in loop expressions are rejected (1/2).
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 12:
+
+ `    for (let x)`
+  Near here ----^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x)
+		;
+%}
+-- End --
+
+
+Ensure that too short for-in loop expressions are rejected (2/2).
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 15:
+
+ `    for (let x, y)`
+  Near here -------^
+
+
+-- End --
+
+-- Testcase --
+{%
+	for (let x, y)
+		;
+%}
+-- End --
diff --git a/tests/custom/00_syntax/17_while_loop b/tests/custom/00_syntax/17_while_loop
new file mode 100644
index 0000000..1e68d6b
--- /dev/null
+++ b/tests/custom/00_syntax/17_while_loop
@@ -0,0 +1,71 @@
+Utpl implements C-style while loops which run as long as the condition
+is fulfilled.
+
+Like with for-loops, an alternative syntax form suitable for template
+blocks is supported.
+
+
+-- Expect stdout --
+A simple counting while-loop:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+
+A counting while-loop using the alternative syntax:
+Iteration 0
+Iteration 1
+Iteration 2
+Iteration 3
+Iteration 4
+Iteration 5
+Iteration 6
+Iteration 7
+Iteration 8
+Iteration 9
+-- End --
+
+-- Testcase --
+A simple counting while-loop:
+{%
+	i = 0;
+	while (i < 10) {
+		print("Iteration ");
+		print(i);
+		print("\n");
+		i++;
+	}
+%}
+
+If the loop body consists of only one statement, the curly braces
+may be omitted:
+{%
+	i = 0;
+	while (i < 10)
+		print("Iteration ", i++, "\n");
+%}
+
+A counting while-loop using the alternative syntax:
+{% while (x < 10): -%}
+Iteration {{ "" + x++ }}
+{% endwhile %}
+-- End --
diff --git a/tests/custom/00_syntax/18_if_condition b/tests/custom/00_syntax/18_if_condition
new file mode 100644
index 0000000..9e02767
--- /dev/null
+++ b/tests/custom/00_syntax/18_if_condition
@@ -0,0 +1,121 @@
+Utpl implements C-style if/else conditions and ?: ternary statements.
+
+Like with for- and while-loops, an alternative syntax form suitable
+for template blocks is supported.
+
+
+-- Expect stdout --
+This should print "one":
+one
+
+This should print "two":
+two
+
+Multiple conditions can be used by chaining if/else statements:
+three
+
+If the conditional block consists of only one statement, the curly
+braces may be omitted:
+two
+
+An if-condition using the alternative syntax:
+Variable x has another value.
+
+
+An if-condition using the special "elif" keyword in alternative syntax mode:
+Variable x was set to five.
+
+
+Ternary expressions function similar to if/else statements but
+only allow for a single expression in the true and false branches:
+Variable x is one
+-- End --
+
+-- Testcase --
+This should print "one":
+{%
+	x = 0;
+
+	if (x == 0) {
+		print("one");
+	}
+	else {
+		print("two");
+	}
+%}
+
+
+This should print "two":
+{%
+	x = 1;
+
+	if (x == 0) {
+		print("one");
+	}
+	else {
+		print("two");
+	}
+%}
+
+
+Multiple conditions can be used by chaining if/else statements:
+{%
+	x = 2;
+
+	if (x == 0) {
+		print("one");
+	}
+	else if (x == 1) {
+		print("two");
+	}
+	else if (x == 2) {
+		print("three");
+	}
+	else {
+		print("four");
+	}
+%}
+
+
+If the conditional block consists of only one statement, the curly
+braces may be omitted:
+{%
+	x = 5;
+
+	if (x == 0)
+		print("one");
+	else
+		print("two");
+%}
+
+
+An if-condition using the alternative syntax:
+{% if (x == 1): -%}
+Variable x was set to one.
+{% else -%}
+Variable x has another value.
+{% endif %}
+
+
+An if-condition using the special "elif" keyword in alternative syntax mode:
+{% if (x == 0): -%}
+Variable x was set to zero.
+{% elif (x == 1): -%}
+Variable x was set to one.
+{% elif (x == 5): -%}
+Variable x was set to five.
+{% else -%}
+Variable x has another value.
+{% endif %}
+
+
+Ternary expressions function similar to if/else statements but
+only allow for a single expression in the true and false branches:
+{%
+	x = 1;
+	s = (x == 1) ? "Variable x is one" : "Variable x has another value";
+
+	print(s);
+%}
+
+-- End --
diff --git a/tests/custom/00_syntax/19_arrow_functions b/tests/custom/00_syntax/19_arrow_functions
new file mode 100644
index 0000000..102c527
--- /dev/null
+++ b/tests/custom/00_syntax/19_arrow_functions
@@ -0,0 +1,124 @@
+Besides the ordinary ES5-like function declarations, utpl supports ES6 inspired
+arrow function syntax as well. Such arrow functions are useful for callbacks to functions such as replace(), map() or filter().
+
+-- Expect stdout --
+() => { ... }
+test
+(a, b) => { ... }
+3
+(...args) => { ... }
+15
+(a) => { ... }
+10
+(a) => { ... }
+36
+-- End --
+
+-- Testcase --
+{%
+
+	// assign arrow function to variable
+	test1_fn = () => {
+		return "test";
+	};
+
+	// assign arrow function with parameters
+	test2_fn = (a, b) => {
+		return a + b;
+	};
+
+	// nesting functions is legal
+	test3_fn = (...args) => {
+		nested_fn = (a, b) => {
+			return a * b;
+		};
+
+		return args[0] + nested_fn(args[0], args[1]);
+	};
+
+	// parentheses may be omitted if arrow function takes only one argument
+	test4_fn = a => {
+		a * 2;
+	};
+
+	// curly braces may be omitted if function body is a single expression
+	test5_fn = a => a * a;
+
+	print(join("\n", [
+		test1_fn,
+		test1_fn(),
+		test2_fn,
+		test2_fn(1, 2),
+		test3_fn,
+		test3_fn(3, 4),
+		test4_fn,
+		test4_fn(5),
+		test5_fn,
+		test5_fn(6)
+	]), "\n");
+%}
+-- End --
+
+
+While the main advantage of arrow functions is the compact syntax, another
+important difference to normal functions is the "this" context behaviour -
+arrow functions do not have an own "this" context and simply inherit it from
+the outer calling scope.
+
+-- Expect stdout --
+this is set to obj: true
+arrow function uses outher this: true
+normal function has own this: true
+arrow function as method has no this: true
+-- End --
+
+-- Testcase --
+{%
+	obj = {
+		method: function() {
+			let that = this;
+			let arr = () => {
+				print("arrow function uses outher this: ", that == this, "\n");
+			};
+			let fn = function() {
+				print("normal function has own this: ", that != this, "\n");
+			};
+
+			print("this is set to obj: ", this == obj, "\n");
+
+			arr();
+			fn();
+		},
+
+		arrowfn: () => {
+			print("arrow function as method has no this: ", this == null, "\n");
+		}
+	};
+
+	obj.method();
+	obj.arrowfn();
+%}
+-- End --
+
+
+Due to the difficulty of recognizing arrow function expressions with an LR(1)
+grammar the parser has to use a generic expression rule on the lhs argument list
+and verify that it does not contain non-label nodes while building the ast. The
+subsequent testcase asserts that case.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 10:
+
+ `    (a + 1) => { print("test\n") }`
+  Near here --^
+
+
+-- End --
+
+-- Testcase --
+{%
+	(a + 1) => { print("test\n") }
+%}
+-- End --
diff --git a/tests/custom/00_syntax/20_list_expressions b/tests/custom/00_syntax/20_list_expressions
new file mode 100644
index 0000000..d5ba459
--- /dev/null
+++ b/tests/custom/00_syntax/20_list_expressions
@@ -0,0 +1,45 @@
+Similar to ES5, utpl's language grammar allows comma separated list expressions
+in various contexts. Unless such lists happen to be part of a function call
+or array construction expression, only the last result of such an expression
+list should be used while still evaluating all sub-expressions, triggering
+side effects such as function calls or variable assignments.
+
+-- Expect stdout --
+4
+[ 1, 3 ]
+{ "a": true, "b": 1 }
+function call
+[ "test", "assigment" ]
+true
+true
+true
+[ 2, 3 ]
+-- End --
+
+-- Testcase --
+{%
+	// only the last value is considered
+	print(1 + (2, 3), "\n");
+
+	// in array constructors, parenthesized lists are reduced to the last value
+	print([ (0, 1), (2, 3) ], "\n");
+
+	// in object constructors, parenthesized lists are reduced to the last value
+	print({ a: (false, true), b: (0, 1) }, "\n");
+
+	// all list expressions are evaluated and may have side effects, even if
+	// results are discareded
+	x = (print("function call\n"), y = "assigment", "test");
+	print([x, y], "\n");
+
+	// property access operates on the last value of a parenthesized list expression
+	print(({foo: false}, {foo: true}).foo, "\n");
+	print(({foo: false}, {foo: true})["foo"], "\n");
+
+	// computed property access uses the last list expression value
+	print(({foo: true})["bar", "baz", "foo"], "\n");
+
+	// same list semantics apply to function call parameters
+	((...args) => print(args, "\n"))((1, 2), 3);
+%}
+-- End --
diff --git a/tests/custom/00_syntax/21_regex_literals b/tests/custom/00_syntax/21_regex_literals
new file mode 100644
index 0000000..6d85e97
--- /dev/null
+++ b/tests/custom/00_syntax/21_regex_literals
@@ -0,0 +1,89 @@
+Regex literals are enclosed in forward slashes and may contain zero
+or more trailing flag characters. Interpretation of escape sequences
+within regular expression literals is subject of the underlying
+regular expression engine.
+
+-- Expect stdout --
+[ "/Hello world/", "/test/gis", "/test/g", "/test1 \\\/ test2/", "/\\x31\n\\.\u0007\b\\c\\u2600\\\\/" ]
+-- End --
+
+-- Testcase --
+{%
+	print([
+		/Hello world/,				// A very simple expression
+		/test/gsi,					// Regular expression flags
+		/test/gg,					// Repeated flags
+		/test1 \/ test2/,			// Escaped forward slash
+		/\x31\n\.\a\b\c\u2600\\/	// Ensure that escape sequences are passed as-is
+	], "\n");
+%}
+-- End --
+
+
+Testing regular expression type.
+
+-- Expect stdout --
+regexp
+-- End --
+
+-- Testcase --
+{{ type(/foo/) }}
+-- End --
+
+
+Testing invalid flag characters.
+
+-- Expect stderr --
+Syntax error: Unexpected token
+Expecting ';'
+In line 2, byte 8:
+
+ `    /test/x`
+            ^-- Near here
+
+
+-- End --
+
+-- Testcase --
+{%
+	/test/x
+%}
+-- End --
+
+
+Testing unclosed regular expression.
+
+-- Expect stderr --
+Syntax error: Unterminated string
+In line 2, byte 2:
+
+ `    /foo \/`
+      ^-- Near here
+
+
+-- End --
+
+-- Testcase --
+{%
+	/foo \/
+%}
+-- End --
+
+
+Testing regex compilation errors.
+
+-- Expect stderr --
+Syntax error: Unmatched \{
+In line 2, byte 3:
+
+ `     /foo {/`
+       ^-- Near here
+
+
+-- End --
+
+-- Testcase --
+{%
+	 /foo {/
+%}
+-- End --