[dev.cmdgo] all: merge master (5e6a7e9) into dev.cmdgo

Merge List:

+ 2021-08-26 5e6a7e9b86 embed: remove reference to global variables in docs
+ 2021-08-26 166b691b65 cmd/compile/internal/types2: remove need for instance (struct)
+ 2021-08-26 d6bdae33e9 cmd/compile/internal/types2: address some TODOs (cleanup)
+ 2021-08-26 770df2e18d crypto/tls: fix typo in PreferServerCipherSuites comment
+ 2021-08-26 a6ff433d6a cmd/go: pass -gcflags after other flags generated by the go command
+ 2021-08-25 4f2620285d cmd/compile/internal/types2: fix type set printing and add test
+ 2021-08-25 0ac64f6d70 cmd/compile/internal/types2: rename IsMethodSet to IsConstraint (cleanup)
+ 2021-08-25 4068fb6c21 cmd/compile: always accept 1.18 syntax but complain if not 1.18
+ 2021-08-25 bf0bc4122f go/types, types2: don't re-evaluate context string for each function argument (optimization)
+ 2021-08-25 4158e88f64 cmd/compile/internal/syntax: fix position of type parameter field
+ 2021-08-25 647bef6c59 go/types: implement NewTypeList and use it instead of composite literals
+ 2021-08-25 6cf1d5d0fa cmd/compile: generic SSA rules for simplifying 2 and 3 operand integer arithmetic expressions
+ 2021-08-25 5baf60d472 bytes, strings: optimize Trim for single byte cutsets
+ 2021-08-25 3d667671ad cmd/compile: fix function contains no TParam in generic function
+ 2021-08-25 4f2ebfe34b cmd/compile: allow embed into any byte slice type
+ 2021-08-25 d2f002cb39 time/format: avoid growslice in time.String()/time.GoString()
+ 2021-08-25 08d4cc20ca cmd/compile: fix stencil call expression.
+ 2021-08-25 099b819085 cmd/compile: fix CheckSize() calculation for -G=3 and stencils
+ 2021-08-25 e1fcf8857e test: add test that caused gofrontend compiler crash
+ 2021-08-25 d37b8dedf7 test: add test case that gofrontend miscompiled
+ 2021-08-25 41b99dab0f os/user: don't skip TestLookupGroup if supported
+ 2021-08-25 de1c934b97 cmd/compile: fix checkptr false positive for (*[Big]T)(ptr)[:n:n] pattern
+ 2021-08-24 54cdef1f10 reflect: add MapIter.SetKey and MapIter.SetValue
+ 2021-08-24 5d863f89fe cmd/compile: simplify bad conversion check

Change-Id: I29ab927f0e47f44d82f9307c642900f75f4f678f

6 files changed, 19 insertions, 10 deletions

diff --git a/src/go/types/call.go b/src/go/types/call.go
index 87eeef444b..fdecafb781 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -347,8 +347,11 @@ func (check *Checker) arguments(call *ast.CallExpr, sig *Signature, targs []Type
 	}
 
 	// check arguments
-	for i, a := range args {
-		check.assignment(a, sigParams.vars[i].typ, check.sprintf("argument to %s", call.Fun))
+	if len(args) > 0 {
+		context := check.sprintf("argument to %s", call.Fun)
+		for i, a := range args {
+			check.assignment(a, sigParams.vars[i].typ, context)
+		}
 	}
 
 	return
diff --git a/src/go/types/check.go b/src/go/types/check.go
index 909bf8d52d..ab3a388e9f 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -407,7 +407,7 @@ func (check *Checker) recordInferred(call ast.Expr, targs []Type, sig *Signature
 	assert(call != nil)
 	assert(sig != nil)
 	if m := check.Inferred; m != nil {
-		m[call] = Inferred{&TypeList{targs}, sig}
+		m[call] = Inferred{NewTypeList(targs), sig}
 	}
 }
 
diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go
index 3ee09b7e84..5f691d5246 100644
--- a/src/go/types/instantiate.go
+++ b/src/go/types/instantiate.go
@@ -131,7 +131,7 @@ func (check *Checker) instance(pos token.Pos, typ Type, targs []Type) (res Type)
 
 		tname := NewTypeName(pos, t.obj.pkg, t.obj.name, nil)
 		named := check.newNamed(tname, t, nil, nil, nil) // methods and tparams are set when named is loaded
-		named.targs = &TypeList{targs}
+		named.targs = NewTypeList(targs)
 		named.instance = &instance{pos}
 		if check != nil {
 			check.typMap[h] = named
diff --git a/src/go/types/predicates.go b/src/go/types/predicates.go
index 2f4ef9dace..d4055bb0cc 100644
--- a/src/go/types/predicates.go
+++ b/src/go/types/predicates.go
@@ -312,16 +312,14 @@ func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
 				return false
 			}
 
-			if nargs := len(xargs); nargs > 0 {
+			if len(xargs) > 0 {
 				// Instances are identical if their original type and type arguments
 				// are identical.
 				if !Identical(x.orig, y.orig) {
 					return false
 				}
-				for i := 0; i < nargs; i++ {
-					xa := xargs[i]
-					ya := yargs[i]
-					if !Identical(xa, ya) {
+				for i, xa := range xargs {
+					if !Identical(xa, yargs[i]) {
 						return false
 					}
 				}
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 8b8d6fb82a..1c53cdaf2c 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -233,7 +233,7 @@ func (subst *subster) typ(typ Type) Type {
 		// It's ok to provide a nil *Checker because the newly created type
 		// doesn't need to be (lazily) expanded; it's expanded below.
 		named := (*Checker)(nil).newNamed(tname, t.orig, nil, t.tparams, t.methods) // t is loaded, so tparams and methods are available
-		named.targs = &TypeList{newTArgs}
+		named.targs = NewTypeList(newTArgs)
 		subst.typMap[h] = named
 		t.expand(subst.typMap) // must happen after typMap update to avoid infinite recursion
 
diff --git a/src/go/types/typelists.go b/src/go/types/typelists.go
index a8181404bf..ef8ea1f32b 100644
--- a/src/go/types/typelists.go
+++ b/src/go/types/typelists.go
@@ -27,6 +27,14 @@ func (l *TParamList) list() []*TypeParam {
 // TypeList holds a list of types.
 type TypeList struct{ types []Type }
 
+// NewTypeList returns a new TypeList with the types in list.
+func NewTypeList(list []Type) *TypeList {
+	if len(list) == 0 {
+		return nil
+	}
+	return &TypeList{list}
+}
+
 // Len returns the number of types in the list.
 // It is safe to call on a nil receiver.
 func (l *TypeList) Len() int { return len(l.list()) }