inlineimport: implement inlineimport

Signed-off-by: João Lourenço <[email protected]>

source/taurus/inlineimport.d

@@ -0,0 +1,85 @@
+module taurus.inlineimport;
+
+/**
+Imports a symbol from a module inline. Useful for module dependencies with little
+usage.
+
+Checks are done in every symbol, meaning the sequence will fail on the first
+invalid symbol. $(BR)
+`From` should be used When compiled in **betterC**. Because `from` checks valid
+symbols from the start, the program fails if some module depends on something
+that isn't supported in **betterC**.
+- The following do not compile under `betterC`:
+	- **`from.std.traits.isIntegral!byte`**
+	- **`from.std.isIntegral!byte`**
+	- **`From!"std".isIntegral!byte`**
+
+- The correct way to import is to specify the starting point with `From`:
+	- **`From!"std.traits".isIntegral!byte`**
+
+Params: mod = module to search from.
+
+Examples:
+---
+assert(from.std.traits.isIntegral!byte);
+assert(From!"std.array".split("Hello.World", ".") == ["Hello", "World"]);
+
+assert(!__traits(compiles, from.not.exists)); // fails at 'not'
+---
+*/
+enum From(string mod) = FromImpl!mod.init;
+enum from = From!null; ///
+
+version (D_BetterC) {} else
+///
+@safe pure nothrow unittest
+{
+	assert(from.std.array.split("Hello.World", ".") == ["Hello", "World"]);
+	assert(From!"std.array".split("Hello.World", ".") == ["Hello", "World"]);
+
+	assert(from.std.split("Hello.World", ".") == ["Hello", "World"]);
+	assert(From!"std".split("Hello.World", ".") == ["Hello", "World"]);
+
+	assert(!__traits(compiles, from._does.not.exist));
+}
+
+///
+private struct FromImpl(string mod)
+{
+	template opDispatch(string sym)
+	{
+		/*
+		order is important:
+		- mod is empty -> enum FromImpl!sym
+		- mod.sym is valid -> enum FromImpl!mod.sym
+		- mod : sym is valid -> alias sym
+		*/
+
+		static if (!mod.length)
+		{
+			static if(!isModule!sym)
+				alias opDispatch = fail!("Unbale to locate module '" ~ sym ~ "'");
+			else
+				enum opDispatch = FromImpl!sym.init;
+		}
+
+		else static if (isModule!(mod, ".", sym))
+			enum opDispatch = FromImpl!(mod ~ "." ~ sym).init;
+
+		else
+		{
+			static if(!inModule)
+				alias opDispatch = fail!("Symbol '" ~ sym ~ "' not found in module '" ~ mod ~ "'");
+			else
+				mixin("import ", mod, ":", sym, "; alias opDispatch = ", sym, ";");
+		}
+
+		private enum isModule(T ...) = __traits(compiles, { mixin("import ", T, ";"); });
+		private enum inModule = __traits(compiles, { mixin("import ", mod, ":", sym, ";"); });
+
+		private template fail(string msg)
+		{
+			noreturn fail(T ...)(auto ref T t) { static assert (false, msg); }
+		}
+	}
+}