test cases

compiler/test/fail_compilation/interpolatedexpressionsequence_postfix.d

@@ -0,0 +1,13 @@
+/* TEST_OUTPUT:
+---
+interpolatedexpressionsequence_postfix.d(10): Error: String postfixes on interpolated expression sequences are not allowed.
+interpolatedexpressionsequence_postfix.d(11): Error: String postfixes on interpolated expression sequences are not allowed.
+interpolatedexpressionsequence_postfix.d(12): Error: String postfixes on interpolated expression sequences are not allowed.
+---
+*/
+void main() {
+    // all postfixes are banned
+    auto c = i"foo"c;
+    auto w = i"foo"w;
+    auto d = i"foo"d;
+}

compiler/test/runnable/interpolatedexpressionsequence.d

@@ -0,0 +1,38 @@
+import core.interpolation;
+
+alias AliasSeq(T...) = T;
+
+void main() {
+	int a = 1;
+	string b = "one";
+	// parser won't permit alias = i".." directly; i"..." is meant to
+	// be used as a function/template parameter at this time.
+	alias expr = AliasSeq!i"$a $(b)";
+	// elements from the source code are available at compile time, so
+	// we static assert those, but the values, of course, are different
+	static assert(expr[0] == InterpolationHeader());
+	static assert(expr[1] == InterpolatedExpression!"a"());
+	assert(expr[2] == a); // actual value not available at compile time
+	static assert(expr[3] == InterpolatedLiteral!" "());
+	// the parens around the expression are not included
+	static assert(expr[4] == InterpolatedExpression!"b"());
+	assert(expr[5] == b); // actual value not available at compile time
+	static assert(expr[6] == InterpolationFooter());
+
+	// it does currently allow `auto` to be used, it creates a value tuple
+	// you can embed any D expressions inside the parenthesis, and the
+	// token is not ended until you get the *outer* ) and ".
+	auto thing = i"$b $("$" ~ ')' ~ `"`)";
+	string s;
+	foreach(item; thing)
+		// all the items provided by core.interpolation have
+		// toString to return an appropriate value
+		//
+		// then this particular example only has embedded strings
+		// and chars, to we can append them directly
+		static if(__traits(hasMember, item, "toString"))
+			s ~= item.toString();
+		else
+			s ~= item;
+	assert(s == "one $)\"");
+}