Ensure generic constraints are checked before inner extension. (#7685)

* Ensure generic constraints are checked before inner extension.

* Add warning for non-standard generic extension.

* Fix tests.

* Fix test.

* Ban interface types from equality constraints.

* Fix.

2 files changed, 53 insertions, 0 deletions

diff --git a/tests/diagnostics/generic-constraint-equality-right-hand-side.slang b/tests/diagnostics/generic-constraint-equality-right-hand-side.slang
new file mode 100644
index 000000000..c49fe2035
--- /dev/null
+++ b/tests/diagnostics/generic-constraint-equality-right-hand-side.slang
@@ -0,0 +1,36 @@
+//TEST:SIMPLE(filecheck=CHECK):
+interface IGen<A>
+{
+    associatedtype TB;
+    int getVal();
+}
+
+interface Wrapper<A>
+{}
+
+struct Foo1<A> : IGen<A>
+{
+    typealias TB = Wrapper<A>; // `Wrapper<int>` also fails.
+    int val = 0;
+    int getVal()
+    {
+       return val;
+    }
+}
+
+struct Logic<A1, C1 : IGen<A1>>
+{
+    int val = 0;
+}
+
+extension<A, C1> Logic<A, C1>
+    where C1 : IGen<A>
+    //CHECK: ([[# @LINE+1]]): error 30404: 
+    where C1.TB == Wrapper<int>
+{
+    [mutating]
+    void setVal(int dataIn)
+    {
+        val = dataIn;
+    }
+}
diff --git a/tests/diagnostics/non-standard-extension.slang b/tests/diagnostics/non-standard-extension.slang
new file mode 100644
index 000000000..d6a4350a4
--- /dev/null
+++ b/tests/diagnostics/non-standard-extension.slang
@@ -0,0 +1,17 @@
+//TEST:SIMPLE(filecheck=CHECK): -warnings-as-errors 30856
+
+interface ICompatibleWith<T> {}
+interface IBase {}
+struct INT : IBase {}
+struct FLOAT : IBase {}
+
+extension<EX : IBase> EX : ICompatibleWith<INT> {}
+extension<EY : IBase> EY : ICompatibleWith<FLOAT> {}
+
+struct VECTOR<T> {}
+
+// CHECK: ([[# @LINE+1]]): error 30856: the extension is non-standard
+extension<T, U : ICompatibleWith<T>> VECTOR<U> : ICompatibleWith<VECTOR<T>> {}
+
+void main()
+{}
\ No newline at end of file