[dev.unified] cmd/compile/internal/walk: RType fields for range assignments

This CL adds extra fields to RangeStmt that can be used when
desugaring into primitive assignment statements. This will allow the
frontend to wire up all of the RTTI necessary, pulling from
dictionaries as necessary.

Updates #53328.

Change-Id: Iab0e3029ff18c947782ff24f71ef20b2b5cb8305
Reviewed-on: https://go-review.googlesource.com/c/go/+/415518
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ir/stmt.go

@@ -350,6 +350,14 @@ type RangeStmt struct {
 	Body     Nodes
 	HasBreak bool
 	Prealloc *Name
+
+	// When desugaring the RangeStmt during walk, the assignments to Key
+	// and Value may require OCONVIFACE operations. If so, these fields
+	// will be copied to their respective ConvExpr fields.
+	KeyTypeWord   Node `mknode:"-"`
+	KeySrcRType   Node `mknode:"-"`
+	ValueTypeWord Node `mknode:"-"`
+	ValueSrcRType Node `mknode:"-"`
 }
 
 func NewRangeStmt(pos src.XPos, key, value, x Node, body []Node) *RangeStmt {

src/cmd/compile/internal/walk/range.go

@@ -305,7 +305,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 
 // rangeAssign returns "n.Key = key".
 func rangeAssign(n *ir.RangeStmt, key ir.Node) ir.Node {
-	// TODO(mdempsky): Implicit conversions for test/typeparam/mdempsky/17.go.
+	key = rangeConvert(n, n.Key.Type(), key, n.KeyTypeWord, n.KeySrcRType)
 	return ir.NewAssignStmt(n.Pos(), n.Key, key)
 }
 
@@ -313,10 +313,26 @@ func rangeAssign(n *ir.RangeStmt, key ir.Node) ir.Node {
 func rangeAssign2(n *ir.RangeStmt, key, value ir.Node) ir.Node {
 	// Use OAS2 to correctly handle assignments
 	// of the form "v1, a[v1] = range".
-	// TODO(mdempsky): Implicit conversions for test/typeparam/mdempsky/17.go.
+	key = rangeConvert(n, n.Key.Type(), key, n.KeyTypeWord, n.KeySrcRType)
+	value = rangeConvert(n, n.Value.Type(), value, n.ValueTypeWord, n.ValueSrcRType)
 	return ir.NewAssignListStmt(n.Pos(), ir.OAS2, []ir.Node{n.Key, n.Value}, []ir.Node{key, value})
 }
 
+// rangeConvert returns src, converted to dst if necessary. If a
+// conversion is necessary, then typeWord and srcRType are copied to
+// their respective ConvExpr fields.
+func rangeConvert(nrange *ir.RangeStmt, dst *types.Type, src, typeWord, srcRType ir.Node) ir.Node {
+	src = typecheck.Expr(src)
+	if dst.Kind() == types.TBLANK || types.Identical(dst, src.Type()) {
+		return src
+	}
+
+	n := ir.NewConvExpr(nrange.Pos(), ir.OCONV, dst, src)
+	n.TypeWord = typeWord
+	n.SrcRType = srcRType
+	return typecheck.Expr(n)
+}
+
 // isMapClear checks if n is of the form:
 //
 //	for k := range m {