go/types, types2: remove remaining mentions of core type in error messages

The implementatiom still calls coreType in places and refers to
"core types" in comments, but user-visible error messages don't
know about core types anymore.

This brings the user-visible part of the implementation in sync with
the spec which doesn't have the notion of core types anymore.

For #70128.

Change-Id: I14bc6767a83e8f54b10ebe99a7df0b98cd9fca87
Reviewed-on: https://go-review.googlesource.com/c/go/+/654395
Auto-Submit: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>

Author: griesemer

src/cmd/compile/internal/types2/index.go

@@ -217,7 +217,7 @@ func (check *Checker) sliceExpr(x *operand, e *syntax.SliceExpr) {
 	length := int64(-1) // valid if >= 0
 	switch u := coreString(x.typ).(type) {
 	case nil:
-		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no core type", x, x.typ)
+		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no common underlying type", x, x.typ)
 		x.mode = invalid
 		return
 

src/cmd/compile/internal/types2/infer.go

@@ -265,7 +265,7 @@ func (check *Checker) infer(pos syntax.Pos, tparams []*TypeParam, targs []Type,
 					}
 				case single && !core.tilde:
 					if traceInference {
-						u.tracef("-> set type parameter %s to constraint core type %s", tpar, core.typ)
+						u.tracef("-> set type parameter %s to constraint's common underlying type %s", tpar, core.typ)
 					}
 					// The corresponding type argument tx is unknown and the core term
 					// describes a single specific type and no tilde.

src/cmd/compile/internal/types2/signature.go

@@ -45,7 +45,7 @@ func NewSignatureType(recv *Var, recvTypeParams, typeParams []*TypeParam, params
 		}
 		core := coreString(params.At(n - 1).typ)
 		if _, ok := core.(*Slice); !ok && !isString(core) {
-			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as core type", core.String()))
+			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as common underlying type", core.String()))
 		}
 	}
 	sig := &Signature{recv: recv, params: params, results: results, variadic: variadic}

src/go/types/index.go

@@ -219,7 +219,7 @@ func (check *Checker) sliceExpr(x *operand, e *ast.SliceExpr) {
 	length := int64(-1) // valid if >= 0
 	switch u := coreString(x.typ).(type) {
 	case nil:
-		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no core type", x, x.typ)
+		check.errorf(x, NonSliceableOperand, invalidOp+"cannot slice %s: %s has no common underlying type", x, x.typ)
 		x.mode = invalid
 		return
 

src/go/types/infer.go

@@ -58,7 +58,7 @@ func NewSignatureType(recv *Var, recvTypeParams, typeParams []*TypeParam, params
 		}
 		core := coreString(params.At(n - 1).typ)
 		if _, ok := core.(*Slice); !ok && !isString(core) {
-			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as core type", core.String()))
+			panic(fmt.Sprintf("got %s, want variadic parameter with unnamed slice type or string as common underlying type", core.String()))
 		}
 	}
 	sig := &Signature{recv: recv, params: params, results: results, variadic: variadic}

src/go/types/signature.go

@@ -134,11 +134,11 @@ func _[T interface{ ~string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR "
 type myByte1 []byte
 type myByte2 []byte
 func _[T interface{ []byte | myByte1 | myByte2 }] (x T, i, j, k int) { var _ T = x[i:j:k] }
-func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x /* ERROR "no core type" */ [i:j:k] }
+func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x /* ERROR "no common underlying type" */ [i:j:k] }
 
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j] }
 func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR "3-index slice of string" */ ] }
-func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x /* ERROR "no core type" */ [i:j] }
+func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x /* ERROR "no common underlying type" */ [i:j] }
 
 // len/cap built-ins