[dev.typeparams] cmd/compile: allow inlining in instantiated functions

Change markType to scan generic types and methods, so that inlineable
functions inside generic functions/methods will be properly marked for
export, which means inlining inside instantiated functions will work
correctly.

Also, fix handling of closures for instantiated functions. Some code
needs to be adjusted, since instantiated functions/methods are compiled
as if in the package of the source generic function/type, rather than in
the local package. When we create the closure struct, we want to make
sure that the .F field has the same package as the other fields for the
closure variables. Also, we need to disable a check in tcCompLit() when
being done for an instantiated function, since fields of the closure
struct will be from the source package, not the local package.

Re-enabled part of the orderedmapsimp test that was disabled because of
these issues.

Change-Id: Ic4dba8917da0a36b17c0bdb69d6d6edfdf14104a
Reviewed-on: https://go-review.googlesource.com/c/go/+/324331
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/noder/decl.go

@@ -109,6 +109,16 @@ func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
 	}
 
 	g.funcBody(fn, decl.Recv, decl.Type, decl.Body)
+	if fn.Type().HasTParam() && fn.Body != nil {
+		// Set pointers to the dcls/body of a generic function/method in
+		// the Inl struct, so it is marked for export, is available for
+		// stenciling, and works with Inline_Flood().
+		fn.Inl = &ir.Inline{
+			Cost: 1,
+			Dcl:  fn.Dcl,
+			Body: fn.Body,
+		}
+	}
 
 	out.Append(fn)
 }