and %#g is 6; for %g it is the smallest number of digits necessary to identify
the value uniquely.

For complex numbers, the width and precision apply to the two
components independently and the result is parenthesized, so %f applied
to 1.2+3.4i produces (1.200000+3.400000i).

When formatting a single integer code point or a rune string (type []rune)
with %q, invalid Unicode code points are changed to the Unicode replacement

// be incomplete.
type Info struct {
	// Types maps expressions to their types, and for constant
	// expressions, also their values. Invalid expressions are
	// omitted.
	//
	// For (possibly parenthesized) identifiers denoting built-in
	// functions, the recorded signatures are call-site specific:
	// if the call result is not a constant, the recorded type is
	// an argument-specific signature. Otherwise, the recorded type

	case *ast.ParenExpr:
		// name(x) combines but we are making sure at
		// the call site that x is never parenthesized.
		panic("unexpected parenthesized expression")
	}
	return false
}

// isTypeElem reports whether x is a (possibly parenthesized) type element expression.
// The result is false if x could be a type element OR an ordinary (value) expression.
func isTypeElem(x ast.Expr) bool {

// that identifier. The result is nil if it is the blank identifier,
// and Typ[Invalid] if it is an invalid lhs expression.
func (check *Checker) lhsVar(lhs syntax.Expr) Type {
	// Determine if the lhs is a (possibly parenthesized) identifier.
	ident, _ := syntax.Unparen(lhs).(*syntax.Name)

	// Don't evaluate lhs if it is the blank identifier.
	if ident != nil && ident.Value == "_" {
		check.recordDef(ident, nil)
		return nil
	}

	go ( /* ERROR "expression in go must not be parenthesized" */ gos())
	go gos()
	var c chan int
	go close(c)
	go len /* ERROR "go discards result" */ (c)
}

func defers() {
	defer 1; /* ERROR "must be function call" */
	defer int /* ERROR "defer requires function call, not conversion" */ (0)
	defer ( /* ERROR "expression in defer must not be parenthesized" */ defers())
	defer defers()
	var c chan int

// successive submatches of the expression. Submatches are matches of
// parenthesized subexpressions (also known as capturing groups) within the
// regular expression, numbered from left to right in order of opening
// parenthesis. Submatch 0 is the match of the entire expression, submatch 1 is
// the match of the first parenthesized subexpression, and so on.
//

		fun
	  The result is the value of invoking the function, fun(). The return
	  types and values behave as in methods. Functions and function
	  names are described below.
	- A parenthesized instance of one the above, for grouping. The result
	  may be accessed by a field or map key invocation.
		print (.F1 arg1) (.F2 arg2)
		(.StructValuedMethod "arg").Field

 * Can be combined with other parsers in the usual way and its delegate can be set at a later moment in time.
 *
 * It can also be used to create recursive parsers.
 * For example, a parser for a balanced parenthesized symbolic expression can be defined as:
 * ```kotlin
 * var parser by reference<String>()
 * parser = paren(parser) + token(IDENTIFIER) { tokenText }
 * ```
 *

	}
	if m := check.Types; m != nil {
		m[x] = TypeAndValue{mode, typ, val}
	}
}

func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
	// f must be a (possibly parenthesized, possibly qualified)
	// identifier denoting a built-in (including unsafe's non-constant
	// functions Add and Slice): record the signature for f and possible
	// children.
	for {

		tSpace,
		mkItem(itemChar, ","),
		tSpace,
		mkItem(itemVariable, "$w"),
		tSpace,
		mkItem(itemDeclare, ":="),
		tSpace,
		mkItem(itemNumber, "3"),
		tRight,
		tEOF,
	}},
	{"field of parenthesized expression", "{{(.X).Y}}", []item{
		tLeft,
		tLpar,
		mkItem(itemField, ".X"),
		tRpar,
		mkItem(itemField, ".Y"),
		tRight,
		tEOF,
	}},