go/types: use error_.errorf for reporting related error information

Use error_.errorf for reporting related error information rather than
inlining the "\n\t". This aligns go/types with types2 in cases where the
related information has no position information. In other cases,
go/types needs to report a "continuation error" (starting with '\t') so
that users can access multiple error positions.

Change-Id: Ica98466596c374e0c1e502e7227c8d8c803b4c22
Reviewed-on: https://go-review.googlesource.com/c/go/+/400825
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>

src/go/types/assignments.go

diff --git a/src/go/types/assignments.go b/src/go/types/assignments.go
index 101e868..98d7563 100644
--- a/src/go/types/assignments.go
+++ b/src/go/types/assignments.go
@@ -9,6 +9,7 @@
 import (
 	"fmt"
 	"go/ast"
+	"go/token"
 	"strings"
 )
 
@@ -339,11 +340,10 @@
 			} else if len(rhs) > 0 {
 				at = rhs[len(rhs)-1].expr // report at last value
 			}
-			check.errorf(at, _WrongResultCount, "%s return values\n\thave %s\n\twant %s",
-				qualifier,
-				check.typesSummary(operandTypes(rhs), false),
-				check.typesSummary(varTypes(lhs), false),
-			)
+			err := newErrorf(at, _WrongResultCount, "%s return values", qualifier)
+			err.errorf(token.NoPos, "have %s", check.typesSummary(operandTypes(rhs), false))
+			err.errorf(token.NoPos, "want %s", check.typesSummary(varTypes(lhs), false))
+			check.report(err)
 			return
 		}
 		if compilerErrorMessages {

src/go/types/call.go

diff --git a/src/go/types/call.go b/src/go/types/call.go
index 5160317..3c7c322 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -368,11 +368,10 @@
 		if sig.params != nil {
 			params = sig.params.vars
 		}
-		check.errorf(at, _WrongArgCount, "%s arguments in call to %s\n\thave %s\n\twant %s",
-			qualifier, call.Fun,
-			check.typesSummary(operandTypes(args), false),
-			check.typesSummary(varTypes(params), sig.variadic),
-		)
+		err := newErrorf(at, _WrongArgCount, "%s arguments in call to %s", qualifier, call.Fun)
+		err.errorf(token.NoPos, "have %s", check.typesSummary(operandTypes(args), false))
+		err.errorf(token.NoPos, "want %s", check.typesSummary(varTypes(params), sig.variadic))
+		check.report(err)
 		return
 	}
 

src/go/types/conversions.go

diff --git a/src/go/types/conversions.go b/src/go/types/conversions.go
index 65691cf..362c8fd 100644
--- a/src/go/types/conversions.go
+++ b/src/go/types/conversions.go
@@ -8,6 +8,7 @@
 
 import (
 	"go/constant"
+	"go/token"
 	"unicode"
 )
 
@@ -74,7 +75,9 @@
 		if compilerErrorMessages {
 			if cause != "" {
 				// Add colon at end of line if we have a following cause.
-				check.errorf(x, _InvalidConversion, "cannot convert %s to type %s:\n\t%s", x, T, cause)
+				err := newErrorf(x, _InvalidConversion, "cannot convert %s to type %s:", x, T)
+				err.errorf(token.NoPos, cause)
+				check.report(err)
 			} else {
 				check.errorf(x, _InvalidConversion, "cannot convert %s to type %s", x, T)
 			}