[dev.typeparams] cmd/compile: directly set some simple expression types

This CL updates irgen to directly set the type for a bunch of basic
expressions that are easy to handle already. Trickier rewrites are
still handled with typecheck.Expr, but responsibility of calling that
is pushed down to the conversion of individual operations.

Change-Id: I774ac6ab4c72ad854860ab5c741867dd42a066b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/285058
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 36 insertions, 19 deletions

diff --git a/src/cmd/compile/internal/noder/expr.go b/src/cmd/compile/internal/noder/expr.go
index d5177ead06..be592003e1 100644
--- a/src/cmd/compile/internal/noder/expr.go
+++ b/src/cmd/compile/internal/noder/expr.go
@@ -43,15 +43,36 @@ func (g *irgen) expr(expr syntax.Expr) ir.Node {
 		base.FatalfAt(g.pos(expr), "unrecognized type-checker result")
 	}
 
+	// The gc backend expects all expressions to have a concrete type, and
+	// types2 mostly satisfies this expectation already. But there are a few
+	// cases where the Go spec doesn't require converting to concrete type,
+	// and so types2 leaves them untyped. So we need to fix those up here.
+	typ := tv.Type
+	if basic, ok := typ.(*types2.Basic); ok && basic.Info()&types2.IsUntyped != 0 {
+		switch basic.Kind() {
+		case types2.UntypedNil:
+			// ok; can appear in type switch case clauses
+			// TODO(mdempsky): Handle as part of type switches instead?
+		case types2.UntypedBool:
+			typ = types2.Typ[types2.Bool] // expression in "if" or "for" condition
+		case types2.UntypedString:
+			typ = types2.Typ[types2.String] // argument to "append" or "copy" calls
+		default:
+			base.FatalfAt(g.pos(expr), "unexpected untyped type: %v", basic)
+		}
+	}
+
 	// Constant expression.
 	if tv.Value != nil {
-		return Const(g.pos(expr), g.typ(tv.Type), tv.Value)
+		return Const(g.pos(expr), g.typ(typ), tv.Value)
 	}
 
-	// TODO(mdempsky): Remove dependency on typecheck.Expr.
-	n := typecheck.Expr(g.expr0(tv.Type, expr))
-	if !g.match(n.Type(), tv.Type, tv.HasOk()) {
-		base.FatalfAt(g.pos(expr), "expected %L to have type %v", n, tv.Type)
+	n := g.expr0(typ, expr)
+	if n.Typecheck() != 1 {
+		base.FatalfAt(g.pos(expr), "missed typecheck: %+v", n)
+	}
+	if !g.match(n.Type(), typ, tv.HasOk()) {
+		base.FatalfAt(g.pos(expr), "expected %L to have type %v", n, typ)
 	}
 	return n
 }
@@ -64,7 +85,8 @@ func (g *irgen) expr0(typ types2.Type, expr syntax.Expr) ir.Node {
 		if _, isNil := g.info.Uses[expr].(*types2.Nil); isNil {
 			return Nil(pos, g.typ(typ))
 		}
-		return g.use(expr)
+		// TODO(mdempsky): Remove dependency on typecheck.Expr.
+		return typecheck.Expr(g.use(expr))
 
 	case *syntax.CompositeLit:
 		return g.compLit(typ, expr)
@@ -83,13 +105,14 @@ func (g *irgen) expr0(typ types2.Type, expr syntax.Expr) ir.Node {
 		// Qualified identifier.
 		if name, ok := expr.X.(*syntax.Name); ok {
 			if _, ok := g.info.Uses[name].(*types2.PkgName); ok {
-				return g.use(expr.Sel)
+				// TODO(mdempsky): Remove dependency on typecheck.Expr.
+				return typecheck.Expr(g.use(expr.Sel))
 			}
 		}
 
 		// TODO(mdempsky/danscales): Use g.info.Selections[expr]
 		// to resolve field/method selection. See CL 280633.
-		return ir.NewSelectorExpr(pos, ir.OXDOT, g.expr(expr.X), g.name(expr.Sel))
+		return typecheck.Expr(ir.NewSelectorExpr(pos, ir.OXDOT, g.expr(expr.X), g.name(expr.Sel)))
 	case *syntax.SliceExpr:
 		return Slice(pos, g.expr(expr.X), g.expr(expr.Index[0]), g.expr(expr.Index[1]), g.expr(expr.Index[2]))
 
@@ -131,16 +154,9 @@ func (g *irgen) exprs(exprs []syntax.Expr) []ir.Node {
 
 func (g *irgen) compLit(typ types2.Type, lit *syntax.CompositeLit) ir.Node {
 	if ptr, ok := typ.Underlying().(*types2.Pointer); ok {
-		if _, isNamed := typ.(*types2.Named); isNamed {
-			// TODO(mdempsky): Questionable, but this is
-			// currently allowed by cmd/compile, go/types,
-			// and gccgo:
-			//
-			//	type T *struct{}
-			//	var _ = []T{{}}
-			base.FatalfAt(g.pos(lit), "defined-pointer composite literal")
-		}
-		return ir.NewAddrExpr(g.pos(lit), g.compLit(ptr.Elem(), lit))
+		n := ir.NewAddrExpr(g.pos(lit), g.compLit(ptr.Elem(), lit))
+		n.SetOp(ir.OPTRLIT)
+		return typed(g.typ(typ), n)
 	}
 
 	_, isStruct := typ.Underlying().(*types2.Struct)
@@ -159,7 +175,8 @@ func (g *irgen) compLit(typ types2.Type, lit *syntax.CompositeLit) ir.Node {
 		}
 	}
 
-	return ir.NewCompLitExpr(g.pos(lit), ir.OCOMPLIT, ir.TypeNode(g.typ(typ)), exprs)
+	// TODO(mdempsky): Remove dependency on typecheck.Expr.
+	return typecheck.Expr(ir.NewCompLitExpr(g.pos(lit), ir.OCOMPLIT, ir.TypeNode(g.typ(typ)), exprs))
 }
 
 func (g *irgen) funcLit(typ types2.Type, expr *syntax.FuncLit) ir.Node {