exp/types: filling in more blanks

- implemented built-in complex()
- implemented missing expression switch checks

R=rsc
CC=golang-dev
https://golang.org/cl/6920046

6 files changed, 163 insertions, 21 deletions

diff --git a/src/pkg/exp/gotype/gotype_test.go b/src/pkg/exp/gotype/gotype_test.go
index 2d58f32883..8a90082206 100644
--- a/src/pkg/exp/gotype/gotype_test.go
+++ b/src/pkg/exp/gotype/gotype_test.go
@@ -99,9 +99,9 @@ var tests = []string{
 	"encoding/asn1",
 	"encoding/base32",
 	"encoding/base64",
-	// "encoding/binary", // complex() doesn't work yet
+	"encoding/binary",
 	"encoding/csv",
-	// "encoding/gob", // complex() doesn't work yet
+	"encoding/gob",
 	"encoding/hex",
 	"encoding/json",
 	"encoding/pem",
@@ -146,7 +146,7 @@ var tests = []string{
 
 	"math",
 	// "math/big", // investigate
-	// "math/cmplx", // complex doesn't work yet
+	"math/cmplx",
 	"math/rand",
 
 	"mime",
diff --git a/src/pkg/exp/types/builtins.go b/src/pkg/exp/types/builtins.go
index 88267042e4..f86ae6ac38 100644
--- a/src/pkg/exp/types/builtins.go
+++ b/src/pkg/exp/types/builtins.go
@@ -128,13 +128,50 @@ func (check *checker) builtin(x *operand, call *ast.CallExpr, bin *builtin, iota
 		x.mode = novalue
 
 	case _Complex:
+		if !check.complexArg(x) {
+			goto Error
+		}
+
 		var y operand
 		check.expr(&y, args[1], nil, iota)
 		if y.mode == invalid {
 			goto Error
 		}
-		// TODO(gri) handle complex(a, b) like (a + toImag(b))
-		unimplemented()
+		if !check.complexArg(&y) {
+			goto Error
+		}
+
+		check.convertUntyped(x, y.typ)
+		if x.mode == invalid {
+			goto Error
+		}
+		check.convertUntyped(&y, x.typ)
+		if y.mode == invalid {
+			goto Error
+		}
+
+		if !isIdentical(x.typ, y.typ) {
+			check.invalidArg(x.pos(), "mismatched types %s and %s", x.typ, y.typ)
+			goto Error
+		}
+
+		if x.mode == constant && y.mode == constant {
+			x.val = binaryOpConst(x.val, toImagConst(y.val), token.ADD, false)
+		} else {
+			x.mode = value
+		}
+
+		switch underlying(x.typ).(*Basic).Kind {
+		case Float32:
+			x.typ = Typ[Complex64]
+		case Float64:
+			x.typ = Typ[Complex128]
+		case UntypedInt, UntypedRune, UntypedFloat:
+			x.typ = Typ[UntypedComplex]
+		default:
+			check.invalidArg(x.pos(), "float32 or float64 arguments expected")
+			goto Error
+		}
 
 	case _Copy:
 		// TODO(gri) implements checks
@@ -361,3 +398,12 @@ func unparen(x ast.Expr) ast.Expr {
 	}
 	return x
 }
+
+func (check *checker) complexArg(x *operand) bool {
+	t, _ := underlying(x.typ).(*Basic)
+	if t != nil && (t.Info&IsFloat != 0 || t.Kind == UntypedInt || t.Kind == UntypedRune) {
+		return true
+	}
+	check.invalidArg(x.pos(), "%s must be a float32, float64, or an untyped non-complex numeric constant", x)
+	return false
+}
diff --git a/src/pkg/exp/types/const.go b/src/pkg/exp/types/const.go
index c678e4749b..cab6bbcbd0 100644
--- a/src/pkg/exp/types/const.go
+++ b/src/pkg/exp/types/const.go
@@ -157,6 +157,22 @@ func makeStringConst(lit string) interface{} {
 	return nil
 }
 
+// toImagConst returns the constant complex(0, x) for a non-complex x.
+func toImagConst(x interface{}) interface{} {
+	var im *big.Rat
+	switch x := x.(type) {
+	case int64:
+		im = big.NewRat(x, 1)
+	case *big.Int:
+		im = new(big.Rat).SetFrac(x, int1)
+	case *big.Rat:
+		im = x
+	default:
+		unreachable()
+	}
+	return complex{rat0, im}
+}
+
 // isZeroConst reports whether the value of constant x is 0.
 // x must be normalized.
 //
diff --git a/src/pkg/exp/types/stmt.go b/src/pkg/exp/types/stmt.go
index e2c6448deb..edad87f2e0 100644
--- a/src/pkg/exp/types/stmt.go
+++ b/src/pkg/exp/types/stmt.go
@@ -427,25 +427,58 @@ func (check *checker) stmt(s ast.Stmt) {
 	case *ast.SwitchStmt:
 		check.optionalStmt(s.Init)
 		var x operand
-		if s.Tag != nil {
-			check.expr(&x, s.Tag, nil, -1)
-		} else {
-			// TODO(gri) should provide a position (see IncDec) for good error messages
-			x.mode = constant
-			x.typ = Typ[UntypedBool]
-			x.val = true
+		tag := s.Tag
+		if tag == nil {
+			// create true tag value and position it at the opening { of the switch
+			tag = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true", Obj: Universe.Lookup("true")}
 		}
+		check.expr(&x, tag, nil, -1)
 
 		check.multipleDefaults(s.Body.List)
+		seen := make(map[interface{}]token.Pos)
 		for _, s := range s.Body.List {
 			clause, _ := s.(*ast.CaseClause)
 			if clause == nil {
 				continue // error reported before
 			}
-			for _, expr := range clause.List {
-				var y operand
-				check.expr(&y, expr, nil, -1)
-				// TODO(gri) x and y must be comparable
+			if x.mode != invalid {
+				for _, expr := range clause.List {
+					x := x // copy of x (don't modify original)
+					var y operand
+					check.expr(&y, expr, nil, -1)
+					if y.mode == invalid {
+						continue // error reported before
+					}
+					// If we have a constant case value, it must appear only
+					// once in the switch statement. Determine if there is a
+					// duplicate entry, but only report an error there are no
+					// other errors.
+					var dupl token.Pos
+					if y.mode == constant {
+						// TODO(gri) This code doesn't work correctly for
+						//           large integer, floating point, or
+						//           complex values - the respective struct
+						//           comparison is shallow. Need to use a
+						//           has function to index the seen map.
+						dupl = seen[y.val]
+						seen[y.val] = y.pos()
+					}
+					// TODO(gri) The convertUntyped call pair below appears in other places. Factor!
+					// Order matters: By comparing y against x, error positions are at the case values.
+					check.convertUntyped(&y, x.typ)
+					if y.mode == invalid {
+						continue // error reported before
+					}
+					check.convertUntyped(&x, y.typ)
+					if x.mode == invalid {
+						continue // error reported before
+					}
+					check.comparison(&y, &x, token.EQL)
+					if y.mode != invalid && dupl.IsValid() {
+						check.errorf(y.pos(), "%s is duplicate case in switch\n\tprevious case at %s",
+							&y, check.fset.Position(dupl))
+					}
+				}
 			}
 			check.stmtList(clause.Body)
 		}
diff --git a/src/pkg/exp/types/testdata/builtins.src b/src/pkg/exp/types/testdata/builtins.src
index a07af89f41..a9518530de 100644
--- a/src/pkg/exp/types/testdata/builtins.src
+++ b/src/pkg/exp/types/testdata/builtins.src
@@ -46,10 +46,33 @@ func _close() {
 }
 
 func _complex() {
-	_0 := complex /* ERROR "argument" */ ()
-	_1 := complex /* ERROR "argument" */ (1)
-	_2 := complex(1, 2)
-	// TODO(gri) add tests checking types
+	var i32 int32
+	var f32 float32
+	var f64 float64
+	var c64 complex64
+	_ = complex /* ERROR "argument" */ ()
+	_ = complex /* ERROR "argument" */ (1)
+	_ = complex(true /* ERROR "invalid argument" */ , 0)
+	_ = complex(i32 /* ERROR "invalid argument" */ , 0)
+	_ = complex("foo" /* ERROR "invalid argument" */ , 0)
+	_ = complex(c64 /* ERROR "invalid argument" */ , 0)
+	_ = complex(0, true /* ERROR "invalid argument" */ )
+	_ = complex(0, i32 /* ERROR "invalid argument" */ )
+	_ = complex(0, "foo" /* ERROR "invalid argument" */ )
+	_ = complex(0, c64 /* ERROR "invalid argument" */ )
+	_ = complex(f32, f32)
+	_ = complex(f32, 1)
+	_ = complex(f32, 1.0)
+	_ = complex(f32, 'a')
+	_ = complex(f64, f64)
+	_ = complex(f64, 1)
+	_ = complex(f64, 1.0)
+	_ = complex(f64, 'a')
+	_ = complex(f32 /* ERROR "mismatched types" */, f64)
+	_ = complex(f64 /* ERROR "mismatched types" */, f32)
+	_ = complex(1, 1)
+	_ = complex(1, 1.1)
+	_ = complex(1, 'a')
 	complex /* ERROR "not used" */ (1, 2)
 }
 
diff --git a/src/pkg/exp/types/testdata/stmt0.src b/src/pkg/exp/types/testdata/stmt0.src
index d3cc3acce4..c0e023671b 100644
--- a/src/pkg/exp/types/testdata/stmt0.src
+++ b/src/pkg/exp/types/testdata/stmt0.src
@@ -101,7 +101,31 @@ func _switches() {
 	default /* ERROR "multiple defaults" */ :
 	}
 
-	// TODO(gri) more tests
+	switch {
+	case 1  /* ERROR "cannot convert" */ :
+	}
+
+	switch int32(x) {
+	case 1, 2:
+	case x /* ERROR "cannot compare" */ :
+	}
+
+	switch x {
+	case 1 /* ERROR "overflows int" */ << 100:
+	}
+
+	switch x {
+	case 1:
+	case 1 /* ERROR "duplicate case" */ :
+	case 2, 3, 4:
+	case 1 /* ERROR "duplicate case" */ :
+	}
+
+	// TODO(gri) duplicate 64bit values that don't fit into an int64 are not yet detected
+	switch uint64(x) {
+	case 1<<64-1:
+	case 1<<64-1:
+	}
 }
 
 type I interface {