Bug 17503 – is-expression pattern in static if matches too many types

In the following example, the static if branch is taken for both T=Vector!(int, N) and T=Vector!(float, N), while it should only match Vector!(float,N) ----------------------------------------------------- struct Vector(T, int N) {} alias vec3 = Vector!(float, 3); alias ivec3 = Vector!(int, 3); struct Test(T) { void test() { static if (is(T == Vector!(float, N), int N)) { pragma(msg, typeof(this).stringof, ".."); } } } alias TestVec3 = Test!vec3; alias TestIVec3 = Test!ivec3; void main() { TestVec3 tv3; TestIVec3 tiv3; } ----------------------------------------------------- Compiler output: Test!(Vector!(float, 3)).. Test!(Vector!(int, 3)).. ----------------------------------------------------- Expected Compiler output: Test!(Vector!(float, 3)).. ----------------------------------------------------- Link: http://asm.dlang.org/#compilers:!((compiler:dmd2071,options:'',sourcez:FAZwLgTgrgxmAEA1ApnA9hAFAFQDTwEsA7BAOQEp5gBvAX2GAEMAbAxkeAN1QGZ4BeJKjAYAhJgBmzNIzD4e5ANxNW7Qtxh9BKdBHHE58BctCRYCbMnA5yNYPC5oCAE3hgrYTLYfV7D%2BOCyBDCEEvCYBCA4AtrCYpLSsvgU%2BAbwFJS%2B/v4ADhCMAOYAtoyYRSAF%2BGAAnjnIaBKYYAAWkeQAdOAQxAUN%2BABE7e39SlTZ9A709CpsHJbgOlrw82CiGjzKLLPLHgCSiwI74KIE6yacTq4lxF52DisHYJwbfiv7vG6nL7RAAAA%3D%3D)),filterAsm:(binary:!t),version:3

Reduced: ---- struct Vector(T, int N) {} static assert(!is(Vector!(int, 3) == Vector!(float, N), int N)); /* fails; should pass */ ----

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