[dev.typeparams] cmd/compile: formalize "hidden parameters" idea

This CL formalizes the closure-var trick used for method-value
wrappers to be reusable for defining other functions that take hidden
parameters via the closure-context register. In particular, it:

1. Adds a new ir.NewHiddenParam function for creating hidden
parameters.

2. Changes ir.NewClosureVar to copy Type/Typecheck from the closure
variable, so that callers can needing to manually copy these.

3. Updates existing code accordingly (i.e., method-value wrappers to
start using ir.NewHiddenParam, and closure builders to stop copying
types).

Longer term, I anticipate using this to pass dictionaries to stenciled
functions within unified IR.

Change-Id: I9da3ffdb2a26d15c6e89a21b4e080686d6dc872c
Reviewed-on: https://go-review.googlesource.com/c/go/+/332612
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/cmd/compile/internal/escape/escape.go b/src/cmd/compile/internal/escape/escape.go
index 04d0c2356c..61e0121a40 100644
--- a/src/cmd/compile/internal/escape/escape.go
+++ b/src/cmd/compile/internal/escape/escape.go
@@ -183,8 +183,14 @@ func (b *batch) initFunc(fn *ir.Func) {
 
 	// Allocate locations for local variables.
 	for _, n := range fn.Dcl {
-		if n.Op() == ir.ONAME {
-			e.newLoc(n, false)
+		e.newLoc(n, false)
+	}
+
+	// Also for hidden parameters (e.g., the ".this" parameter to a
+	// method value wrapper).
+	if fn.OClosure == nil {
+		for _, n := range fn.ClosureVars {
+			e.newLoc(n.Canonical(), false)
 		}
 	}