cmd/compile: pass type checker error codes in the compiler

Pass type checker error codes to base.ErrorfAt function calls
in the compiler (but don't do anything yet with the code).

Also, provide error codes to base.ErrorfAt calls in the
compiler as needed.

This opens the door towards reporting the error code and/or
providing a link/reference to more detailed explanations
(see internal/types/errors/codes.go).

Change-Id: I0ff9368d8163499ffdac6adfe8331fdc4a19b4b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/475198
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/base/print.go

@@ -7,6 +7,7 @@ package base
 import (
 	"fmt"
 	"internal/buildcfg"
+	"internal/types/errors"
 	"os"
 	"runtime/debug"
 	"sort"
@@ -105,11 +106,11 @@ func sameline(a, b src.XPos) bool {
 
 // Errorf reports a formatted error at the current line.
 func Errorf(format string, args ...interface{}) {
-	ErrorfAt(Pos, format, args...)
+	ErrorfAt(Pos, 0, format, args...)
 }
 
 // ErrorfAt reports a formatted error message at pos.
-func ErrorfAt(pos src.XPos, format string, args ...interface{}) {
+func ErrorfAt(pos src.XPos, code errors.Code, format string, args ...interface{}) {
 	msg := fmt.Sprintf(format, args...)
 
 	if strings.HasPrefix(msg, "syntax error") {

src/cmd/compile/internal/escape/escape.go

@@ -303,7 +303,7 @@ func (b *batch) finish(fns []*ir.Func) {
 		if loc.escapes {
 			if n.Op() == ir.ONAME {
 				if base.Flag.CompilingRuntime {
-					base.ErrorfAt(n.Pos(), "%v escapes to heap, not allowed in runtime", n)
+					base.ErrorfAt(n.Pos(), 0, "%v escapes to heap, not allowed in runtime", n)
 				}
 				if base.Flag.LowerM != 0 {
 					base.WarnfAt(n.Pos(), "moved to heap: %v", n)

src/cmd/compile/internal/escape/graph.go

@@ -218,7 +218,7 @@ func (e *escape) newLoc(n ir.Node, transient bool) *location {
 		base.Fatalf("e.curfn isn't set")
 	}
 	if n != nil && n.Type() != nil && n.Type().NotInHeap() {
-		base.ErrorfAt(n.Pos(), "%v is incomplete (or unallocatable); stack allocation disallowed", n.Type())
+		base.ErrorfAt(n.Pos(), 0, "%v is incomplete (or unallocatable); stack allocation disallowed", n.Type())
 	}
 
 	if n != nil && n.Op() == ir.ONAME {

src/cmd/compile/internal/ir/func.go

@@ -331,7 +331,7 @@ func ClosureDebugRuntimeCheck(clo *ClosureExpr) {
 		}
 	}
 	if base.Flag.CompilingRuntime && clo.Esc() == EscHeap && !clo.IsGoWrap {
-		base.ErrorfAt(clo.Pos(), "heap-allocated closure %s, not allowed in runtime", FuncName(clo.Func))
+		base.ErrorfAt(clo.Pos(), 0, "heap-allocated closure %s, not allowed in runtime", FuncName(clo.Func))
 	}
 }
 

src/cmd/compile/internal/noder/irgen.go

@@ -6,6 +6,7 @@ package noder
 
 import (
 	"fmt"
+	"internal/types/errors"
 	"regexp"
 	"sort"
 
@@ -47,7 +48,7 @@ func checkFiles(m posMap, noders []*noder) (*types2.Package, *types2.Info) {
 			if versionErrorRx.MatchString(msg) {
 				msg = fmt.Sprintf("%s (-lang was set to %s; check go.mod)", msg, base.Flag.Lang)
 			}
-			base.ErrorfAt(m.makeXPos(terr.Pos), "%s", msg)
+			base.ErrorfAt(m.makeXPos(terr.Pos), terr.Code, "%s", msg)
 		},
 		Importer: &importer,
 		Sizes:    &gcSizes{},
@@ -72,7 +73,7 @@ func checkFiles(m posMap, noders []*noder) (*types2.Package, *types2.Info) {
 			syntax.Inspect(file, func(n syntax.Node) bool {
 				if n, ok := n.(*syntax.InterfaceType); ok {
 					if f.hasCycle(n.GetTypeInfo().Type.(*types2.Interface)) {
-						base.ErrorfAt(m.makeXPos(n.Pos()), "invalid recursive type: anonymous interface refers to itself (see https://go.dev/issue/56103)")
+						base.ErrorfAt(m.makeXPos(n.Pos()), errors.InvalidTypeCycle, "invalid recursive type: anonymous interface refers to itself (see https://go.dev/issue/56103)")
 
 						for typ := range f.cyclic {
 							f.cyclic[typ] = false // suppress duplicate errors
@@ -106,7 +107,7 @@ func checkFiles(m posMap, noders []*noder) (*types2.Package, *types2.Info) {
 			return ti.pos.Before(tj.pos)
 		})
 		for _, targ := range nihTargs {
-			base.ErrorfAt(targ.pos, "cannot use incomplete (or unallocatable) type as a type argument: %v", targ.typ)
+			base.ErrorfAt(targ.pos, 0, "cannot use incomplete (or unallocatable) type as a type argument: %v", targ.typ)
 		}
 	}
 

src/cmd/compile/internal/noder/noder.go

@@ -65,7 +65,7 @@ func LoadPackage(filenames []string) {
 	var m posMap
 	for _, p := range noders {
 		for e := range p.err {
-			base.ErrorfAt(m.makeXPos(e.Pos), "%s", e.Msg)
+			base.ErrorfAt(m.makeXPos(e.Pos), 0, "%s", e.Msg)
 		}
 		if p.file == nil {
 			base.ErrorExit()

src/cmd/compile/internal/noder/writer.go

@@ -108,7 +108,7 @@ func newPkgWriter(m posMap, pkg *types2.Package, info *types2.Info) *pkgWriter {
 
 // errorf reports a user error about thing p.
 func (pw *pkgWriter) errorf(p poser, msg string, args ...interface{}) {
-	base.ErrorfAt(pw.m.pos(p), msg, args...)
+	base.ErrorfAt(pw.m.pos(p), 0, msg, args...)
 }
 
 // fatalf reports an internal compiler error about thing p.

src/cmd/compile/internal/pkginit/initorder.go

@@ -7,6 +7,7 @@ package pkginit
 import (
 	"container/heap"
 	"fmt"
+	"internal/types/errors"
 	"strings"
 
 	"cmd/compile/internal/base"
@@ -243,7 +244,7 @@ func reportInitLoopAndExit(l []*ir.Name) {
 	}
 	fmt.Fprintf(&msg, "\t%v: %v", ir.Line(l[0]), l[0])
 
-	base.ErrorfAt(l[0].Pos(), msg.String())
+	base.ErrorfAt(l[0].Pos(), errors.InvalidInitCycle, msg.String())
 	base.ErrorExit()
 }
 

src/cmd/compile/internal/ssagen/abi.go

@@ -146,7 +146,7 @@ func (s *SymABIs) GenABIWrappers() {
 		defABI, hasDefABI := s.defs[symName]
 		if hasDefABI {
 			if len(fn.Body) != 0 {
-				base.ErrorfAt(fn.Pos(), "%v defined in both Go and assembly", fn)
+				base.ErrorfAt(fn.Pos(), 0, "%v defined in both Go and assembly", fn)
 			}
 			fn.ABI = defABI
 		}
@@ -251,7 +251,7 @@ func makeABIWrapper(f *ir.Func, wrapperABI obj.ABI) {
 	// below to handle the receiver. Panic if we see this scenario.
 	ft := f.Nname.Type()
 	if ft.NumRecvs() != 0 {
-		base.ErrorfAt(f.Pos(), "makeABIWrapper support for wrapping methods not implemented")
+		base.ErrorfAt(f.Pos(), 0, "makeABIWrapper support for wrapping methods not implemented")
 		return
 	}
 

src/cmd/compile/internal/ssagen/nowb.go

@@ -154,7 +154,7 @@ func (c *nowritebarrierrecChecker) check() {
 		}
 		// Check go:nowritebarrier functions.
 		if fn.Pragma&ir.Nowritebarrier != 0 && fn.WBPos.IsKnown() {
-			base.ErrorfAt(fn.WBPos, "write barrier prohibited")
+			base.ErrorfAt(fn.WBPos, 0, "write barrier prohibited")
 		}
 	}
 
@@ -185,7 +185,7 @@ func (c *nowritebarrierrecChecker) check() {
 				fmt.Fprintf(&err, "\n\t%v: called by %v", base.FmtPos(call.lineno), call.target.Nname)
 				call = funcs[call.target]
 			}
-			base.ErrorfAt(fn.WBPos, "write barrier prohibited by caller; %v%s", fn.Nname, err.String())
+			base.ErrorfAt(fn.WBPos, 0, "write barrier prohibited by caller; %v%s", fn.Nname, err.String())
 			continue
 		}
 

src/cmd/compile/internal/ssagen/pgen.go

@@ -327,9 +327,9 @@ func CheckLargeStacks() {
 	})
 	for _, large := range largeStackFrames {
 		if large.callee != 0 {
-			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args + %d MB callee", large.locals>>20, large.args>>20, large.callee>>20)
+			base.ErrorfAt(large.pos, 0, "stack frame too large (>1GB): %d MB locals + %d MB args + %d MB callee", large.locals>>20, large.args>>20, large.callee>>20)
 		} else {
-			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args", large.locals>>20, large.args>>20)
+			base.ErrorfAt(large.pos, 0, "stack frame too large (>1GB): %d MB locals + %d MB args", large.locals>>20, large.args>>20)
 		}
 	}
 }

src/cmd/compile/internal/staticdata/data.go

@@ -214,7 +214,7 @@ func dstringdata(s *obj.LSym, off int, t string, pos src.XPos, what string) int
 	// causing a cryptic error message by the linker. Check for oversize objects here
 	// and provide a useful error message instead.
 	if int64(len(t)) > 2e9 {
-		base.ErrorfAt(pos, "%v with length %v is too big", what, len(t))
+		base.ErrorfAt(pos, 0, "%v with length %v is too big", what, len(t))
 		return 0
 	}
 

src/cmd/compile/internal/staticdata/embed.go

@@ -31,11 +31,11 @@ func embedFileList(v *ir.Name, kind int) []string {
 		for _, pattern := range e.Patterns {
 			files, ok := base.Flag.Cfg.Embed.Patterns[pattern]
 			if !ok {
-				base.ErrorfAt(e.Pos, "invalid go:embed: build system did not map pattern: %s", pattern)
+				base.ErrorfAt(e.Pos, 0, "invalid go:embed: build system did not map pattern: %s", pattern)
 			}
 			for _, file := range files {
 				if base.Flag.Cfg.Embed.Files[file] == "" {
-					base.ErrorfAt(e.Pos, "invalid go:embed: build system did not map file: %s", file)
+					base.ErrorfAt(e.Pos, 0, "invalid go:embed: build system did not map file: %s", file)
 					continue
 				}
 				if !have[file] {
@@ -57,7 +57,7 @@ func embedFileList(v *ir.Name, kind int) []string {
 
 	if kind == embedString || kind == embedBytes {
 		if len(list) > 1 {
-			base.ErrorfAt(v.Pos(), "invalid go:embed: multiple files for type %v", v.Type())
+			base.ErrorfAt(v.Pos(), 0, "invalid go:embed: multiple files for type %v", v.Type())
 			return nil
 		}
 	}
@@ -109,12 +109,12 @@ func WriteEmbed(v *ir.Name) {
 
 	commentPos := (*v.Embed)[0].Pos
 	if base.Flag.Cfg.Embed.Patterns == nil {
-		base.ErrorfAt(commentPos, "invalid go:embed: build system did not supply embed configuration")
+		base.ErrorfAt(commentPos, 0, "invalid go:embed: build system did not supply embed configuration")
 		return
 	}
 	kind := embedKind(v.Type())
 	if kind == embedUnknown {
-		base.ErrorfAt(v.Pos(), "go:embed cannot apply to var of type %v", v.Type())
+		base.ErrorfAt(v.Pos(), 0, "go:embed cannot apply to var of type %v", v.Type())
 		return
 	}
 
@@ -124,7 +124,7 @@ func WriteEmbed(v *ir.Name) {
 		file := files[0]
 		fsym, size, err := fileStringSym(v.Pos(), base.Flag.Cfg.Embed.Files[file], kind == embedString, nil)
 		if err != nil {
-			base.ErrorfAt(v.Pos(), "embed %s: %v", file, err)
+			base.ErrorfAt(v.Pos(), 0, "embed %s: %v", file, err)
 		}
 		sym := v.Linksym()
 		off := 0
@@ -160,7 +160,7 @@ func WriteEmbed(v *ir.Name) {
 			} else {
 				fsym, size, err := fileStringSym(v.Pos(), base.Flag.Cfg.Embed.Files[file], true, hash)
 				if err != nil {
-					base.ErrorfAt(v.Pos(), "embed %s: %v", file, err)
+					base.ErrorfAt(v.Pos(), 0, "embed %s: %v", file, err)
 				}
 				off = objw.SymPtr(slicedata, off, fsym, 0) // data string
 				off = objw.Uintptr(slicedata, off, uint64(size))

src/cmd/compile/internal/typecheck/const.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"go/constant"
 	"go/token"
+	"internal/types/errors"
 	"math"
 	"math/big"
 	"strings"
@@ -567,7 +568,7 @@ func OrigConst(n ir.Node, v constant.Value) ir.Node {
 		if what == "" {
 			base.Fatalf("unexpected overflow: %v", n.Op())
 		}
-		base.ErrorfAt(n.Pos(), "constant %v overflow", what)
+		base.ErrorfAt(n.Pos(), errors.NumericOverflow, "constant %v overflow", what)
 		n.SetType(nil)
 		return n
 	}

src/cmd/compile/internal/typecheck/dcl.go

@@ -6,6 +6,7 @@ package typecheck
 
 import (
 	"fmt"
+	"internal/types/errors"
 	"sync"
 
 	"cmd/compile/internal/base"
@@ -48,15 +49,15 @@ func Declare(n *ir.Name, ctxt ir.Class) {
 
 	// kludgy: TypecheckAllowed means we're past parsing. Eg reflectdata.methodWrapper may declare out of package names later.
 	if !inimport && !TypecheckAllowed && s.Pkg != types.LocalPkg {
-		base.ErrorfAt(n.Pos(), "cannot declare name %v", s)
+		base.ErrorfAt(n.Pos(), 0, "cannot declare name %v", s)
 	}
 
 	if ctxt == ir.PEXTERN {
 		if s.Name == "init" {
-			base.ErrorfAt(n.Pos(), "cannot declare init - must be func")
+			base.ErrorfAt(n.Pos(), errors.InvalidInitDecl, "cannot declare init - must be func")
 		}
 		if s.Name == "main" && s.Pkg.Name == "main" {
-			base.ErrorfAt(n.Pos(), "cannot declare main - must be func")
+			base.ErrorfAt(n.Pos(), errors.InvalidMainDecl, "cannot declare main - must be func")
 		}
 		Target.Externs = append(Target.Externs, n)
 		s.Def = n
@@ -154,7 +155,7 @@ func checkdupfields(what string, fss ...[]*types.Field) {
 				continue
 			}
 			if seen[f.Sym] {
-				base.ErrorfAt(f.Pos, "duplicate %s %s", what, f.Sym.Name)
+				base.ErrorfAt(f.Pos, errors.DuplicateFieldAndMethod, "duplicate %s %s", what, f.Sym.Name)
 				continue
 			}
 			seen[f.Sym] = true

src/cmd/compile/internal/typecheck/stmt.go

@@ -9,6 +9,7 @@ import (
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
+	"internal/types/errors"
 )
 
 func RangeExprType(t *types.Type) *types.Type {
@@ -37,7 +38,7 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 	toomany := false
 	switch t.Kind() {
 	default:
-		base.ErrorfAt(n.Pos(), "cannot range over %L", n.X)
+		base.ErrorfAt(n.Pos(), errors.InvalidRangeExpr, "cannot range over %L", n.X)
 		return
 
 	case types.TARRAY, types.TSLICE:
@@ -50,7 +51,7 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 
 	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())
+			base.ErrorfAt(n.Pos(), errors.InvalidRangeExpr, "invalid operation: range %v (receive from send-only type %v)", n.X, n.X.Type())
 			return
 		}
 
@@ -66,7 +67,7 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 	}
 
 	if toomany {
-		base.ErrorfAt(n.Pos(), "too many variables in range")
+		base.ErrorfAt(n.Pos(), errors.InvalidIterVar, "too many variables in range")
 	}
 
 	do := func(nn ir.Node, t *types.Type) {
@@ -75,7 +76,7 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 				nn.SetType(t)
 			} else if nn.Type() != nil {
 				if op, why := Assignop(t, nn.Type()); op == ir.OXXX {
-					base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t, nn, why)
+					base.ErrorfAt(n.Pos(), errors.InvalidIterVar, "cannot assign type %v to %L in range%s", t, nn, why)
 				}
 			}
 			checkassign(nn)
@@ -185,10 +186,10 @@ assignOK:
 	if len(lhs) != cr {
 		if r, ok := rhs[0].(*ir.CallExpr); ok && len(rhs) == 1 {
 			if r.Type() != nil {
-				base.ErrorfAt(stmt.Pos(), "assignment mismatch: %d variable%s but %v returns %d value%s", len(lhs), plural(len(lhs)), r.X, cr, plural(cr))
+				base.ErrorfAt(stmt.Pos(), errors.WrongAssignCount, "assignment mismatch: %d variable%s but %v returns %d value%s", len(lhs), plural(len(lhs)), r.X, cr, plural(cr))
 			}
 		} else {
-			base.ErrorfAt(stmt.Pos(), "assignment mismatch: %d variable%s but %v value%s", len(lhs), plural(len(lhs)), len(rhs), plural(len(rhs)))
+			base.ErrorfAt(stmt.Pos(), errors.WrongAssignCount, "assignment mismatch: %d variable%s but %v value%s", len(lhs), plural(len(lhs)), len(rhs), plural(len(rhs)))
 		}
 
 		for i := range lhs {
@@ -298,7 +299,7 @@ func tcGoDefer(n *ir.GoDeferStmt) {
 		if orig := ir.Orig(n.Call); orig.Op() == ir.OCONV {
 			break
 		}
-		base.ErrorfAt(n.Pos(), "%s discards result of %v", what, n.Call)
+		base.ErrorfAt(n.Pos(), errors.UnusedResults, "%s discards result of %v", what, n.Call)
 		return
 	}
 
@@ -379,7 +380,7 @@ func tcSelect(sel *ir.SelectStmt) {
 		if ncase.Comm == nil {
 			// default
 			if def != nil {
-				base.ErrorfAt(ncase.Pos(), "multiple defaults in select (first at %v)", ir.Line(def))
+				base.ErrorfAt(ncase.Pos(), errors.DuplicateDefault, "multiple defaults in select (first at %v)", ir.Line(def))
 			} else {
 				def = ncase
 			}
@@ -403,7 +404,7 @@ func tcSelect(sel *ir.SelectStmt) {
 					// 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")
+				base.ErrorfAt(pos, errors.InvalidSelectCase, "select case must be receive, send or assign recv")
 
 			case ir.OAS:
 				// convert x = <-c into x, _ = <-c
@@ -417,7 +418,7 @@ func tcSelect(sel *ir.SelectStmt) {
 					}
 				}
 				if n.Y.Op() != ir.ORECV {
-					base.ErrorfAt(n.Pos(), "select assignment must have receive on right hand side")
+					base.ErrorfAt(n.Pos(), errors.InvalidSelectCase, "select assignment must have receive on right hand side")
 					break
 				}
 				oselrecv2(n.X, n.Y, n.Def)
@@ -425,7 +426,7 @@ func tcSelect(sel *ir.SelectStmt) {
 			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")
+					base.ErrorfAt(n.Pos(), errors.InvalidSelectCase, "select assignment must have receive on right hand side")
 					break
 				}
 				n.SetOp(ir.OSELRECV2)
@@ -502,9 +503,9 @@ func tcSwitchExpr(n *ir.SwitchStmt) {
 
 		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)
+				base.ErrorfAt(n.Pos(), errors.InvalidExprSwitch, "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)
+				base.ErrorfAt(n.Pos(), errors.InvalidExprSwitch, "cannot switch on %L", n.Tag)
 			}
 			t = nil
 		}
@@ -515,7 +516,7 @@ func tcSwitchExpr(n *ir.SwitchStmt) {
 		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))
+				base.ErrorfAt(ncase.Pos(), errors.DuplicateDefault, "multiple defaults in switch (first at %v)", ir.Line(defCase))
 			} else {
 				defCase = ncase
 			}
@@ -531,17 +532,17 @@ func tcSwitchExpr(n *ir.SwitchStmt) {
 			}
 
 			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)
+				base.ErrorfAt(ncase.Pos(), errors.MismatchedTypes, "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)
+				base.ErrorfAt(ncase.Pos(), errors.UndefinedOp, "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)
+						base.ErrorfAt(ncase.Pos(), errors.MismatchedTypes, "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())
+						base.ErrorfAt(ncase.Pos(), errors.MismatchedTypes, "invalid case %v in switch (mismatched types %v and bool)", n1, n1.Type())
 					}
 				}
 			}
@@ -556,7 +557,7 @@ func tcSwitchType(n *ir.SwitchStmt) {
 	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)
+		base.ErrorfAt(n.Pos(), errors.InvalidTypeSwitch, "cannot type switch on non-interface value %L", guard.X)
 		t = nil
 	}
 
@@ -564,7 +565,7 @@ func tcSwitchType(n *ir.SwitchStmt) {
 	// 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())
+		base.ErrorfAt(v.Pos(), errors.UnusedVar, "%v declared but not used", v.Sym())
 	}
 
 	var defCase, nilCase ir.Node
@@ -573,7 +574,7 @@ func tcSwitchType(n *ir.SwitchStmt) {
 		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))
+				base.ErrorfAt(ncase.Pos(), errors.DuplicateDefault, "multiple defaults in switch (first at %v)", ir.Line(defCase))
 			} else {
 				defCase = ncase
 			}
@@ -590,7 +591,7 @@ func tcSwitchType(n *ir.SwitchStmt) {
 			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))
+					base.ErrorfAt(ncase.Pos(), errors.DuplicateCase, "multiple nil cases in type switch (first at %v)", ir.Line(nilCase))
 				} else {
 					nilCase = ncase
 				}
@@ -600,18 +601,18 @@ func tcSwitchType(n *ir.SwitchStmt) {
 				continue
 			}
 			if n1.Op() != ir.OTYPE {
-				base.ErrorfAt(ncase.Pos(), "%L is not a type", n1)
+				base.ErrorfAt(ncase.Pos(), errors.NotAType, "%L is not a type", n1)
 				continue
 			}
 			if !n1.Type().IsInterface() && !implements(n1.Type(), t, &missing, &have, &ptr) {
 				if have != nil {
-					base.ErrorfAt(ncase.Pos(), "impossible type switch case: %L cannot have dynamic type %v"+
+					base.ErrorfAt(ncase.Pos(), errors.ImpossibleAssert, "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"+
+					base.ErrorfAt(ncase.Pos(), errors.ImpossibleAssert, "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"+
+					base.ErrorfAt(ncase.Pos(), errors.ImpossibleAssert, "impossible type switch case: %L cannot have dynamic type %v"+
 						" (missing %v method)", guard.X, n1.Type(), missing.Sym)
 				}
 				continue
@@ -659,7 +660,7 @@ func (s *typeSet) add(pos src.XPos, typ *types.Type) {
 
 	ls := typ.LinkString()
 	if prev, ok := s.m[ls]; ok {
-		base.ErrorfAt(pos, "duplicate case %v in type switch\n\tprevious case at %s", typ, base.FmtPos(prev))
+		base.ErrorfAt(pos, errors.DuplicateCase, "duplicate case %v in type switch\n\tprevious case at %s", typ, base.FmtPos(prev))
 		return
 	}
 	s.m[ls] = pos

src/cmd/compile/internal/typecheck/typecheck.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"go/constant"
 	"go/token"
+	"internal/types/errors"
 	"strings"
 
 	"cmd/compile/internal/base"
@@ -286,7 +287,7 @@ func typecheck(n ir.Node, top int) (res ir.Node) {
 						return n
 					}
 				}
-				base.ErrorfAt(n.Pos(), "invalid recursive type alias %v%s", n, cycleTrace(cycle))
+				base.ErrorfAt(n.Pos(), errors.InvalidDeclCycle, "invalid recursive type alias %v%s", n, cycleTrace(cycle))
 			}
 
 		case ir.OLITERAL:
@@ -294,7 +295,7 @@ func typecheck(n ir.Node, top int) (res ir.Node) {
 				base.Errorf("%v is not a type", n)
 				break
 			}
-			base.ErrorfAt(n.Pos(), "constant definition loop%s", cycleTrace(cycleFor(n)))
+			base.ErrorfAt(n.Pos(), errors.InvalidInitCycle, "constant definition loop%s", cycleTrace(cycleFor(n)))
 		}
 
 		if base.Errors() == 0 {

src/cmd/compile/internal/types/size.go

@@ -9,6 +9,7 @@ import (
 
 	"cmd/compile/internal/base"
 	"cmd/internal/src"
+	"internal/types/errors"
 )
 
 var PtrSize int
@@ -84,7 +85,7 @@ func expandiface(t *Type) {
 		case !explicit && Identical(m.Type, prev.Type):
 			return
 		default:
-			base.ErrorfAt(m.Pos, "duplicate method %s", m.Sym.Name)
+			base.ErrorfAt(m.Pos, errors.DuplicateDecl, "duplicate method %s", m.Sym.Name)
 		}
 		methods = append(methods, m)
 	}
@@ -147,7 +148,7 @@ func expandiface(t *Type) {
 	sort.Sort(MethodsByName(methods))
 
 	if int64(len(methods)) >= MaxWidth/int64(PtrSize) {
-		base.ErrorfAt(typePos(t), "interface too large")
+		base.ErrorfAt(typePos(t), 0, "interface too large")
 	}
 	for i, m := range methods {
 		m.Offset = int64(i) * int64(PtrSize)
@@ -212,7 +213,7 @@ func calcStructOffset(errtype *Type, t *Type, o int64, flag int) int64 {
 			maxwidth = 1<<31 - 1
 		}
 		if o >= maxwidth {
-			base.ErrorfAt(typePos(errtype), "type %L too large", errtype)
+			base.ErrorfAt(typePos(errtype), 0, "type %L too large", errtype)
 			o = 8 // small but nonzero
 		}
 	}

src/cmd/compile/internal/types/type.go

@@ -8,6 +8,7 @@ import (
 	"cmd/compile/internal/base"
 	"cmd/internal/src"
 	"fmt"
+	"internal/types/errors"
 	"sync"
 )
 
@@ -1663,7 +1664,7 @@ func (t *Type) SetUnderlying(underlying *Type) {
 	// Double-check use of type as embedded type.
 	if ft.Embedlineno.IsKnown() {
 		if t.IsPtr() || t.IsUnsafePtr() {
-			base.ErrorfAt(ft.Embedlineno, "embedded type cannot be a pointer")
+			base.ErrorfAt(ft.Embedlineno, errors.InvalidPtrEmbed, "embedded type cannot be a pointer")
 		}
 	}
 }

src/cmd/compile/internal/walk/expr.go

@@ -560,7 +560,7 @@ func walkCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
 			fn := arg.(*ir.ConvExpr).X.(*ir.Name)
 			abi := fn.Func.ABI
 			if abi != wantABI {
-				base.ErrorfAt(n.Pos(), "internal/abi.%s expects an %v function, %s is defined as %v", name, wantABI, fn.Sym().Name, abi)
+				base.ErrorfAt(n.Pos(), 0, "internal/abi.%s expects an %v function, %s is defined as %v", name, wantABI, fn.Sym().Name, abi)
 			}
 			var e ir.Node = ir.NewLinksymExpr(n.Pos(), fn.Sym().LinksymABI(abi), types.Types[types.TUINTPTR])
 			e = ir.NewAddrExpr(n.Pos(), e)
@@ -570,7 +570,7 @@ func walkCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
 		// fn is not a defined function. It must be ABIInternal.
 		// Read the address from func value, i.e. *(*uintptr)(idata(fn)).
 		if wantABI != obj.ABIInternal {
-			base.ErrorfAt(n.Pos(), "internal/abi.%s does not accept func expression, which is ABIInternal", name)
+			base.ErrorfAt(n.Pos(), 0, "internal/abi.%s does not accept func expression, which is ABIInternal", name)
 		}
 		arg = walkExpr(arg, init)
 		var e ir.Node = ir.NewUnaryExpr(n.Pos(), ir.OIDATA, arg)