Add basic AST pretty-print visualizer and @print metafunction

Also make `unique`, `shared`, and `nonesuch` be `inline`, closes #685.

And finally fix `token::to_string`'s default to never decorate, all callers passed `true` anyway except the one use in `parse_tree_printer::start(token)`.

Author: hsutter

include/cpp2util.h

@@ -517,14 +517,14 @@ struct {
     [[nodiscard]] auto cpp2_new(auto&& ...args) const -> std::unique_ptr<T> {
         return std::make_unique<T>(CPP2_FORWARD(args)...);
     }
-} unique;
+} inline unique;
 
 [[maybe_unused]] struct {
     template<typename T>
     [[nodiscard]] auto cpp2_new(auto&& ...args) const -> std::shared_ptr<T> {
         return std::make_shared<T>(CPP2_FORWARD(args)...);
     }
-} shared;
+} inline shared;
 
 template<typename T>
 [[nodiscard]] auto cpp2_new(auto&& ...args) -> std::unique_ptr<T> {
@@ -1009,7 +1009,7 @@ inline constexpr auto is( auto const& x, auto const& value ) -> bool
 struct nonesuch_ {
     auto operator==(auto const&) -> bool { return false; }
 };
-constexpr static nonesuch_ nonesuch;
+constexpr inline nonesuch_ nonesuch;
 
 //  The 'as' cast functions are <To, From> so use that order here
 //  If it's confusing, we can switch this to <From, To>

regression-tests/pure2-intro-example-hello-2022.cpp2

@@ -5,7 +5,7 @@ main: () -> int = {
 
     for view do (inout str) {
         len := decorate(str);
-        println(str, len);
+        print_it(str, len);
     }
 }
 
@@ -14,7 +14,7 @@ decorate: (inout thing: _ ) -> int = {
     return thing.ssize();
 }
 
-println: (x: _, len: _) =
+print_it: (x: _, len: _) =
     std::cout
         << ">> " << x
         << " - length "

regression-tests/pure2-print.cpp2

@@ -0,0 +1,90 @@
+
+//  Exercise the pretty-print visualizer for the various grammar elements
+
+outer: @print type = {
+
+    mytype: final type =
+    {
+        protected f: () -> int = 42;
+
+        g: (virtual this, i:int) -> int = {
+            s := "string literal";
+            ret: int = i;
+            p: const * const int = ret&;
+            if p* < 0 {
+                ret = -p*;
+            }
+            ret += strlen(s) - 10 + s.strlen() * (16 / (3 & 2)) % 3;
+
+            m: std::map<const int,std::string> = ();
+            m[0] = "har" as std::string;
+            ret -= h("x", m).length();
+            _ = m;
+
+            return ret;
+        }
+
+        private h: (s: std::string, inout m: std::map<const int,std::string> ) -> std::string
+            [[pre: m.empty() == false || false]]
+            [[pre Bounds: 0 < m.ssize() < 100 && true != false]]
+        = {
+            a := :()={};
+            b := :()={};
+            c := :()={};
+
+            while s.empty() next a() { break; }
+
+            do { } while s.empty() next b();
+
+            label: for m next c() do (_) { continue label; }
+
+            if !s.empty() is (true) { a(); }
+            else if !m.empty() { b(); }
+            else { c(); }
+
+            [[assert: true]]
+
+            return :() -> std::string = (s + m[0])$; ();
+        }
+
+        values: <T> (this, t: T) throws -> (offset: int, name: std::string) = {
+            offset = 53;
+            name = "plugh";
+        }
+
+        operator=: (out this) = { }
+
+        operator=: (out this, that) = { }
+
+        operator=: (implicit out this, _: int) = { }
+
+        variadic: (x...: int) = { }
+    }
+
+    test: () = {
+        var: ::outer::mytype = ();
+        std::cout << var.g(42) << "\n";
+
+        std::cout << inspect var.g(42) -> std::string {
+            is 43 = "forty-and-three";
+            is _  = "default case";
+        } << "\n";
+
+    }
+
+    x: <Ts...: type> type = {
+        tup: std::tuple<Ts...> = ();
+    }
+
+    print: <Args...: type> (inout out: std::ostream, args...: Args) requires sizeof...(Args) >= 0 = {
+        (out << ... << args);
+    }
+
+    all: <Args...: type> (args...: Args) -> bool =
+        (... && args);
+
+}
+
+main: () = {
+    outer::test();
+}

regression-tests/test-results/clang-12/pure2-print.cpp.execution

@@ -0,0 +1,2 @@
+43
+forty-and-three

regression-tests/test-results/clang-12/pure2-print.cpp.output

@@ -0,0 +1,7 @@
+pure2-print.cpp2:50:80: warning: unused parameter 't' [-Wunused-parameter]
+        template<typename T> [[nodiscard]] auto outer::mytype::values(T const& t) const& -> values__ret{
+                                                                               ^
+pure2-print.cpp2:61:53: warning: unused parameter 'x' [-Wunused-parameter]
+        auto outer::mytype::variadic(auto const& ...x) -> void{}
+                                                    ^
+2 warnings generated.

regression-tests/test-results/gcc-10/pure2-print.cpp.output

@@ -0,0 +1,6 @@
+In file included from pure2-print.cpp:7:
+../../../include/cpp2util.h:10005:33: error: expected initializer before ‘static_assert’
+pure2-print.cpp2:80:1: note: in expansion of macro ‘CPP2_REQUIRES_’
+pure2-print.cpp2:79:37: error: no declaration matches ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::cmp_greater_eq(sizeof (Args)..., 0)’
+pure2-print.cpp2:79:37: note: no functions named ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::cmp_greater_eq(sizeof (Args)..., 0)’
+pure2-print.cpp2:4:7: note: ‘class outer’ defined here

regression-tests/test-results/gcc-13/pure2-print.cpp.execution

@@ -0,0 +1,2 @@
+43
+forty-and-three

regression-tests/test-results/gcc-13/pure2-print.cpp.output

@@ -1,3 +1,3 @@
-Microsoft (R) C/C++ Optimizing Compiler Version 19.36.32538 for x86
+Microsoft (R) C/C++ Optimizing Compiler Version 19.37.32824 for x86
 Copyright (C) Microsoft Corporation.  All rights reserved.
 

regression-tests/test-results/msvc-2022/MSVC-version.output

@@ -0,0 +1,2 @@
+43
+forty-and-three