1 files changed, 435 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/typecheck/stmt.go b/src/cmd/compile/internal/typecheck/stmt.go
new file mode 100644
index 0000000000..889ee06d6e
--- /dev/null
+++ b/src/cmd/compile/internal/typecheck/stmt.go
@@ -0,0 +1,435 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typecheck
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// range
+func typecheckrange(n *ir.RangeStmt) {
+	// Typechecking order is important here:
+	// 0. first typecheck range expression (slice/map/chan),
+	//	it is evaluated only once and so logically it is not part of the loop.
+	// 1. typecheck produced values,
+	//	this part can declare new vars and so it must be typechecked before body,
+	//	because body can contain a closure that captures the vars.
+	// 2. decldepth++ to denote loop body.
+	// 3. typecheck body.
+	// 4. decldepth--.
+	typecheckrangeExpr(n)
+
+	// second half of dance, the first half being typecheckrangeExpr
+	n.SetTypecheck(1)
+	ls := n.Vars
+	for i1, n1 := range ls {
+		if n1.Typecheck() == 0 {
+			ls[i1] = AssignExpr(ls[i1])
+		}
+	}
+
+	decldepth++
+	Stmts(n.Body)
+	decldepth--
+}
+
+func typecheckrangeExpr(n *ir.RangeStmt) {
+	n.X = Expr(n.X)
+
+	t := n.X.Type()
+	if t == nil {
+		return
+	}
+	// delicate little dance.  see typecheckas2
+	ls := n.Vars
+	for i1, n1 := range ls {
+		if !ir.DeclaredBy(n1, n) {
+			ls[i1] = AssignExpr(ls[i1])
+		}
+	}
+
+	if t.IsPtr() && t.Elem().IsArray() {
+		t = t.Elem()
+	}
+	n.SetType(t)
+
+	var t1, t2 *types.Type
+	toomany := false
+	switch t.Kind() {
+	default:
+		base.ErrorfAt(n.Pos(), "cannot range over %L", n.X)
+		return
+
+	case types.TARRAY, types.TSLICE:
+		t1 = types.Types[types.TINT]
+		t2 = t.Elem()
+
+	case types.TMAP:
+		t1 = t.Key()
+		t2 = t.Elem()
+
+	case types.TCHAN:
+		if !t.ChanDir().CanRecv() {
+			base.ErrorfAt(n.Pos(), "invalid operation: range %v (receive from send-only type %v)", n.X, n.X.Type())
+			return
+		}
+
+		t1 = t.Elem()
+		t2 = nil
+		if len(n.Vars) == 2 {
+			toomany = true
+		}
+
+	case types.TSTRING:
+		t1 = types.Types[types.TINT]
+		t2 = types.RuneType
+	}
+
+	if len(n.Vars) > 2 || toomany {
+		base.ErrorfAt(n.Pos(), "too many variables in range")
+	}
+
+	var v1, v2 ir.Node
+	if len(n.Vars) != 0 {
+		v1 = n.Vars[0]
+	}
+	if len(n.Vars) > 1 {
+		v2 = n.Vars[1]
+	}
+
+	// this is not only an optimization but also a requirement in the spec.
+	// "if the second iteration variable is the blank identifier, the range
+	// clause is equivalent to the same clause with only the first variable
+	// present."
+	if ir.IsBlank(v2) {
+		if v1 != nil {
+			n.Vars = []ir.Node{v1}
+		}
+		v2 = nil
+	}
+
+	if v1 != nil {
+		if ir.DeclaredBy(v1, n) {
+			v1.SetType(t1)
+		} else if v1.Type() != nil {
+			if op, why := assignop(t1, v1.Type()); op == ir.OXXX {
+				base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t1, v1, why)
+			}
+		}
+		checkassign(n, v1)
+	}
+
+	if v2 != nil {
+		if ir.DeclaredBy(v2, n) {
+			v2.SetType(t2)
+		} else if v2.Type() != nil {
+			if op, why := assignop(t2, v2.Type()); op == ir.OXXX {
+				base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t2, v2, why)
+			}
+		}
+		checkassign(n, v2)
+	}
+}
+
+// select
+func typecheckselect(sel *ir.SelectStmt) {
+	var def ir.Node
+	lno := ir.SetPos(sel)
+	Stmts(sel.Init())
+	for _, ncase := range sel.Cases {
+		ncase := ncase.(*ir.CaseStmt)
+
+		if len(ncase.List) == 0 {
+			// default
+			if def != nil {
+				base.ErrorfAt(ncase.Pos(), "multiple defaults in select (first at %v)", ir.Line(def))
+			} else {
+				def = ncase
+			}
+		} else if len(ncase.List) > 1 {
+			base.ErrorfAt(ncase.Pos(), "select cases cannot be lists")
+		} else {
+			ncase.List[0] = Stmt(ncase.List[0])
+			n := ncase.List[0]
+			ncase.Comm = n
+			ncase.List.Set(nil)
+			oselrecv2 := func(dst, recv ir.Node, colas bool) {
+				n := ir.NewAssignListStmt(n.Pos(), ir.OSELRECV2, nil, nil)
+				n.Lhs = []ir.Node{dst, ir.BlankNode}
+				n.Rhs = []ir.Node{recv}
+				n.Def = colas
+				n.SetTypecheck(1)
+				ncase.Comm = n
+			}
+			switch n.Op() {
+			default:
+				pos := n.Pos()
+				if n.Op() == ir.ONAME {
+					// We don't have the right position for ONAME nodes (see #15459 and
+					// others). Using ncase.Pos for now as it will provide the correct
+					// line number (assuming the expression follows the "case" keyword
+					// on the same line). This matches the approach before 1.10.
+					pos = ncase.Pos()
+				}
+				base.ErrorfAt(pos, "select case must be receive, send or assign recv")
+
+			case ir.OAS:
+				// convert x = <-c into x, _ = <-c
+				// remove implicit conversions; the eventual assignment
+				// will reintroduce them.
+				n := n.(*ir.AssignStmt)
+				if r := n.Y; r.Op() == ir.OCONVNOP || r.Op() == ir.OCONVIFACE {
+					r := r.(*ir.ConvExpr)
+					if r.Implicit() {
+						n.Y = r.X
+					}
+				}
+				if n.Y.Op() != ir.ORECV {
+					base.ErrorfAt(n.Pos(), "select assignment must have receive on right hand side")
+					break
+				}
+				oselrecv2(n.X, n.Y, n.Def)
+
+			case ir.OAS2RECV:
+				n := n.(*ir.AssignListStmt)
+				if n.Rhs[0].Op() != ir.ORECV {
+					base.ErrorfAt(n.Pos(), "select assignment must have receive on right hand side")
+					break
+				}
+				n.SetOp(ir.OSELRECV2)
+
+			case ir.ORECV:
+				// convert <-c into _, _ = <-c
+				n := n.(*ir.UnaryExpr)
+				oselrecv2(ir.BlankNode, n, false)
+
+			case ir.OSEND:
+				break
+			}
+		}
+
+		Stmts(ncase.Body)
+	}
+
+	base.Pos = lno
+}
+
+type typeSet struct {
+	m map[string][]typeSetEntry
+}
+
+func (s *typeSet) add(pos src.XPos, typ *types.Type) {
+	if s.m == nil {
+		s.m = make(map[string][]typeSetEntry)
+	}
+
+	// LongString does not uniquely identify types, so we need to
+	// disambiguate collisions with types.Identical.
+	// TODO(mdempsky): Add a method that *is* unique.
+	ls := typ.LongString()
+	prevs := s.m[ls]
+	for _, prev := range prevs {
+		if types.Identical(typ, prev.typ) {
+			base.ErrorfAt(pos, "duplicate case %v in type switch\n\tprevious case at %s", typ, base.FmtPos(prev.pos))
+			return
+		}
+	}
+	s.m[ls] = append(prevs, typeSetEntry{pos, typ})
+}
+
+type typeSetEntry struct {
+	pos src.XPos
+	typ *types.Type
+}
+
+func typecheckExprSwitch(n *ir.SwitchStmt) {
+	t := types.Types[types.TBOOL]
+	if n.Tag != nil {
+		n.Tag = Expr(n.Tag)
+		n.Tag = DefaultLit(n.Tag, nil)
+		t = n.Tag.Type()
+	}
+
+	var nilonly string
+	if t != nil {
+		switch {
+		case t.IsMap():
+			nilonly = "map"
+		case t.Kind() == types.TFUNC:
+			nilonly = "func"
+		case t.IsSlice():
+			nilonly = "slice"
+
+		case !types.IsComparable(t):
+			if t.IsStruct() {
+				base.ErrorfAt(n.Pos(), "cannot switch on %L (struct containing %v cannot be compared)", n.Tag, types.IncomparableField(t).Type)
+			} else {
+				base.ErrorfAt(n.Pos(), "cannot switch on %L", n.Tag)
+			}
+			t = nil
+		}
+	}
+
+	var defCase ir.Node
+	var cs constSet
+	for _, ncase := range n.Cases {
+		ncase := ncase.(*ir.CaseStmt)
+		ls := ncase.List
+		if len(ls) == 0 { // default:
+			if defCase != nil {
+				base.ErrorfAt(ncase.Pos(), "multiple defaults in switch (first at %v)", ir.Line(defCase))
+			} else {
+				defCase = ncase
+			}
+		}
+
+		for i := range ls {
+			ir.SetPos(ncase)
+			ls[i] = Expr(ls[i])
+			ls[i] = DefaultLit(ls[i], t)
+			n1 := ls[i]
+			if t == nil || n1.Type() == nil {
+				continue
+			}
+
+			if nilonly != "" && !ir.IsNil(n1) {
+				base.ErrorfAt(ncase.Pos(), "invalid case %v in switch (can only compare %s %v to nil)", n1, nilonly, n.Tag)
+			} else if t.IsInterface() && !n1.Type().IsInterface() && !types.IsComparable(n1.Type()) {
+				base.ErrorfAt(ncase.Pos(), "invalid case %L in switch (incomparable type)", n1)
+			} else {
+				op1, _ := assignop(n1.Type(), t)
+				op2, _ := assignop(t, n1.Type())
+				if op1 == ir.OXXX && op2 == ir.OXXX {
+					if n.Tag != nil {
+						base.ErrorfAt(ncase.Pos(), "invalid case %v in switch on %v (mismatched types %v and %v)", n1, n.Tag, n1.Type(), t)
+					} else {
+						base.ErrorfAt(ncase.Pos(), "invalid case %v in switch (mismatched types %v and bool)", n1, n1.Type())
+					}
+				}
+			}
+
+			// Don't check for duplicate bools. Although the spec allows it,
+			// (1) the compiler hasn't checked it in the past, so compatibility mandates it, and
+			// (2) it would disallow useful things like
+			//       case GOARCH == "arm" && GOARM == "5":
+			//       case GOARCH == "arm":
+			//     which would both evaluate to false for non-ARM compiles.
+			if !n1.Type().IsBoolean() {
+				cs.add(ncase.Pos(), n1, "case", "switch")
+			}
+		}
+
+		Stmts(ncase.Body)
+	}
+}
+
+func typecheckTypeSwitch(n *ir.SwitchStmt) {
+	guard := n.Tag.(*ir.TypeSwitchGuard)
+	guard.X = Expr(guard.X)
+	t := guard.X.Type()
+	if t != nil && !t.IsInterface() {
+		base.ErrorfAt(n.Pos(), "cannot type switch on non-interface value %L", guard.X)
+		t = nil
+	}
+
+	// We don't actually declare the type switch's guarded
+	// declaration itself. So if there are no cases, we won't
+	// notice that it went unused.
+	if v := guard.Tag; v != nil && !ir.IsBlank(v) && len(n.Cases) == 0 {
+		base.ErrorfAt(v.Pos(), "%v declared but not used", v.Sym())
+	}
+
+	var defCase, nilCase ir.Node
+	var ts typeSet
+	for _, ncase := range n.Cases {
+		ncase := ncase.(*ir.CaseStmt)
+		ls := ncase.List
+		if len(ls) == 0 { // default:
+			if defCase != nil {
+				base.ErrorfAt(ncase.Pos(), "multiple defaults in switch (first at %v)", ir.Line(defCase))
+			} else {
+				defCase = ncase
+			}
+		}
+
+		for i := range ls {
+			ls[i] = check(ls[i], ctxExpr|ctxType)
+			n1 := ls[i]
+			if t == nil || n1.Type() == nil {
+				continue
+			}
+
+			var missing, have *types.Field
+			var ptr int
+			if ir.IsNil(n1) { // case nil:
+				if nilCase != nil {
+					base.ErrorfAt(ncase.Pos(), "multiple nil cases in type switch (first at %v)", ir.Line(nilCase))
+				} else {
+					nilCase = ncase
+				}
+				continue
+			}
+			if n1.Op() != ir.OTYPE {
+				base.ErrorfAt(ncase.Pos(), "%L is not a type", n1)
+				continue
+			}
+			if !n1.Type().IsInterface() && !implements(n1.Type(), t, &missing, &have, &ptr) && !missing.Broke() {
+				if have != nil && !have.Broke() {
+					base.ErrorfAt(ncase.Pos(), "impossible type switch case: %L cannot have dynamic type %v"+
+						" (wrong type for %v method)\n\thave %v%S\n\twant %v%S", guard.X, n1.Type(), missing.Sym, have.Sym, have.Type, missing.Sym, missing.Type)
+				} else if ptr != 0 {
+					base.ErrorfAt(ncase.Pos(), "impossible type switch case: %L cannot have dynamic type %v"+
+						" (%v method has pointer receiver)", guard.X, n1.Type(), missing.Sym)
+				} else {
+					base.ErrorfAt(ncase.Pos(), "impossible type switch case: %L cannot have dynamic type %v"+
+						" (missing %v method)", guard.X, n1.Type(), missing.Sym)
+				}
+				continue
+			}
+
+			ts.add(ncase.Pos(), n1.Type())
+		}
+
+		if len(ncase.Vars) != 0 {
+			// Assign the clause variable's type.
+			vt := t
+			if len(ls) == 1 {
+				if ls[0].Op() == ir.OTYPE {
+					vt = ls[0].Type()
+				} else if !ir.IsNil(ls[0]) {
+					// Invalid single-type case;
+					// mark variable as broken.
+					vt = nil
+				}
+			}
+
+			nvar := ncase.Vars[0]
+			nvar.SetType(vt)
+			if vt != nil {
+				nvar = AssignExpr(nvar)
+			} else {
+				// Clause variable is broken; prevent typechecking.
+				nvar.SetTypecheck(1)
+				nvar.SetWalkdef(1)
+			}
+			ncase.Vars[0] = nvar
+		}
+
+		Stmts(ncase.Body)
+	}
+}
+
+// typecheckswitch typechecks a switch statement.
+func typecheckswitch(n *ir.SwitchStmt) {
+	Stmts(n.Init())
+	if n.Tag != nil && n.Tag.Op() == ir.OTYPESW {
+		typecheckTypeSwitch(n)
+	} else {
+		typecheckExprSwitch(n)
+	}
+}