[dev.fuzz] all: merge master (af72ddf) into dev.fuzz

This now includes the fix in CL 350729, which means
we no longer need to skip the test in dev.fuzz.

Conflicts:

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

Merge List:

+ 2021-09-20 af72ddfcd7 cmd/compile: extend dump-to-file to handle "genssa" (asm) case.
+ 2021-09-20 3c764babe7 cmd/go: write go.mod requirements more consistently for go 1.17+
+ 2021-09-20 6268468e02 cmd/link: generate DIE for types referenced only through dictionaries
+ 2021-09-20 6acac8b685 cmd/compile: delay all transforms for generic funcs/methods
+ 2021-09-20 988f18d61d go/types: export Named._Orig as Named.Origin
+ 2021-09-20 b6dddaccd7 cmd/compile: fix transform.AssignOp to deal with tricky case
+ 2021-09-20 9e60c37147 cmd/compile: document register-based ABI for ppc64
+ 2021-09-20 79159f2e83 cmd/compile: fix simplification rules on arm/arm64
+ 2021-09-20 eff27e858b cmd/compile: ensure constant shift amounts are in range for arm
+ 2021-09-20 9ebe7c8ec6 go/test: add a test for issue 48344
+ 2021-09-20 6f35430faa cmd/compile: allow rotates to be merged with logical ops on arm64
+ 2021-09-20 2d9b486420 cmd/compile: update doc at top of iexport.go on the changes for typeparams
+ 2021-09-20 a81b0dc6ee cmd/compile: rename instType -> instanceType
+ 2021-09-20 119213566a cmd/cgo: remove hardcoded '-pie' ldflag for linux/arm
+ 2021-09-20 a83a558733 cmd/compile: fix export/import of range loop.
+ 2021-09-19 315dbd10c9 cmd/compile: fold double negate on arm64
+ 2021-09-19 83b36ffb10 cmd/compile: implement constant rotates on arm64
+ 2021-09-19 771b8ea4f4 cmd/compile: fix missing markHiddenClosureDead in deadcode pass
+ 2021-09-18 c894b442d1 net/rpc: remove warnings on incompatible methods at registration
+ 2021-09-17 4b654c0eec cmd/compile: SSA ".this" variable
+ 2021-09-17 f01721efb9 cmd/compile: remove self copies in tail-call wrappers
+ 2021-09-17 163871feb1 time: re-add space-padded day of year to docs
+ 2021-09-17 ac7c34767d time: support fractional timezone minutes in MarshalBinary
+ 2021-09-17 07b30a4f77 cmd/compile: delay transformAssign if lhs/rhs have typeparam
+ 2021-09-17 c10b980220 cmd/compile: restore tail call for method wrappers
+ 2021-09-17 50e4508269 cmd/compile: fix import/export of Init and Def fields.
+ 2021-09-17 3fa35b5f97 go/types: ensure that we always get a new signature in expandNamed
+ 2021-09-17 3fa7dbeff5 cmd/go: fix GOARCH value in GOAMD64 docs
+ 2021-09-17 974b0166d6 syscall: implement Pipe using pipe2 syscall on all linux platforms
+ 2021-09-17 1a49dcb82f syscall: remove //sysnb comment generating Setreuid for linux/arm64
+ 2021-09-17 cea7a71d40 cmd/compile: fix generic type handling in crawler
+ 2021-09-17 74e384f50d internal/poll: inject a hook into the runtime finalizer to count the closed pipes
+ 2021-09-17 323c6f74d3 log: don't format if writing to io.Discard
+ 2021-09-17 7f36ef0aff cmd/compile/internal/noder: hide TestUnifiedCompare behind -cmp flag
+ 2021-09-17 70493b3eb0 runtime/cgo: save and restore X3 (aka GP) for crosscall1 on riscv64
+ 2021-09-17 6d02ce8584 runtime: fix prettyprinting of parametric types in gdb
+ 2021-09-17 6602c86a38 cmd/internal/obj/riscv: improve instruction validation
+ 2021-09-17 14e812bfc5 syscall: do not use handle lists on windows when NoInheritHandles is true
+ 2021-09-16 8d2a9c32a2 all: remove incorrectly repeated words in comments
+ 2021-09-16 af9da137a9 A+C: update name to real name and add to AUTHORS
+ 2021-09-16 265b59aefd cmd/cgo: for godefs, don't let field prefix removal cause duplicates
+ 2021-09-16 4efdaa7bc7 testing: skip panics when picking the line number for decoration
+ 2021-09-16 e09dcc211a go/types, types2: add an additional shift test case
+ 2021-09-16 5402b4376c spec: fix incorrect type in a shift example
+ 2021-09-16 d09e09bc61 cmd/compile: fixing writebarrier.go for -G=3
+ 2021-09-16 bcdc61d830 cmd/compile: preserve statements better in expandCalls
+ 2021-09-16 48e2b1ea91 cmd/compile: fix LocResults formatting
+ 2021-09-16 b1bedc0774 cmd/go: add GOAMD64 environment variable
+ 2021-09-16 04f5116c98 cmd/go: clean paths before checking same directory
+ 2021-09-16 e7dbe3908e cmd/cgo: add missing tab in exports for a result of void
+ 2021-09-15 cfa233d76b cmd/compile: remove unneeded early transforms, with dictionary change
+ 2021-09-15 59a9a035ff cmd/compile: switch to computing dict format on instantiated functions
+ 2021-09-15 0edc6c4fa0 cmd/internal/obj/ppc64: generate prologue code compatible with new ABI
+ 2021-09-15 03df68d3c3 runtime: fix setting of cpu features for amd64
+ 2021-09-15 6196979365 cmd/go/internal/modload: prevent tidy downgrading disambiguating modules
+ 2021-09-15 72bb8185b5 cmd/compile: emit DWARF info about dictionary entries
+ 2021-09-15 5b48fca1fa cmd/compile: mark wrapper functions with DW_AT_trampoline
+ 2021-09-15 e4dfd788e6 go/internal/gcimporter,cmd/compile: minor clean-up in iimport.go
+ 2021-09-15 4847c47cb8 cmd/compile/internal/types2: eliminate Named.instPos
+ 2021-09-15 3100f54f20 cmd/compile/internal/types2: merge Named type loading and expansion
+ 2021-09-15 738cebb174 cmd/compile/internal/types2: implement Identical for *Union types
+ 2021-09-15 b26d325cb1 cmd/compile/internal/types2: remove some unnecessary loading/expansion of Named types
+ 2021-09-15 9fc28892cb cmd/compile/internal/types2: export TypeHash, return value without blanks
+ 2021-09-15 2da3375e9b runtime: in adjustTimers back up as far as necessary
+ 2021-09-15 c7f2f51fed cmd/go: remove subcommand prefix from error messages
+ 2021-09-15 0bb40b08c4 go/types: implement Identical for *Union types
+ 2021-09-15 cb4e1de021 go/types: minor cleanup of instantiation
+ 2021-09-15 a0f3129466 go/types: instantiate methods when instantiating Named types
+ 2021-09-14 bf26e43d0f go/types: eliminate Named.instPos
+ 2021-09-14 2933c451a0 go/types: merge Named type loading and expansion
+ 2021-09-14 137543bb93 cmd/compile: set IsShape based on type being in the Shapes pkg
+ 2021-09-14 3a72175cdc cmd/compile: fix test/typeparam/mdempsky/4.go for -G=3
+ 2021-09-14 b2c04f0d48 runtime: avoid loop variable capture in test
+ 2021-09-14 181e8cde30 go/internal/gcimporter: remove outdated comment
+ 2021-09-14 8699425b55 syscall: remove use of IN_KUBERNETES in test
+ 2021-09-14 b3c6de9dcd cmd/internal/obj/ppc64: allow VR register arguments to VS registers
+ 2021-09-14 ee91bb8319 cmd/compile: prevent typecheck importer reading type parameter twice
+ 2021-09-14 2953cd0083 go/internal/gcimporter: prevent importReader reading type parameter twice
+ 2021-09-14 b8c802b116 cmd/compile: prevent importReader reading type parameter twice
+ 2021-09-14 4a4221e818 all: remove some unused code
+ 2021-09-14 71adc658de runtime: change time.now to ABIInternal
+ 2021-09-14 146e8d4994 reflect: use Value.Len instead of conversion to slice header
+ 2021-09-13 9a58aa267e spec: fix prose about terminating statements
+ 2021-09-13 42057e9848 cmd/compile: save the note of fields when translating struct
+ 2021-09-13 960d036f8f cmd/go: add missing parenthesis in a call to "PrintVersion"
+ 2021-09-13 81a4fe6fd2 cmd/link/internal/ld: re-enable DWARF tests on solaris/illumos
+ 2021-09-13 f93a63addb reflect: add a floating point section to DeepEqual tests
+ 2021-09-13 a0c409cbc8 reflect: add fast paths for common, simple Kinds to DeepEqual
+ 2021-09-13 ac40c9872f reflect: fix _faststr optimization
+ 2021-09-13 c8a58f29dc cmd/go: add test to check for a potential workspace loading issue
+ 2021-09-13 e74e363a6b strings: add Clone function
+ 2021-09-13 bced369a50 cmd/link: minor code cleanup in dwarf gen
+ 2021-09-13 c3b217a0e5 cmd/go: document 'go install cmd@version' ignores vendor directories
+ 2021-09-12 ad97d204f0 go/types: remove some unnecessary loading/expansion of Named types
+ 2021-09-12 0d8a4bfc96 bufio: add Writer.AvailableBuffer
+ 2021-09-11 23832ba2e2 reflect: optimize for maps with string keys
+ 2021-09-11 a50225a0dc bufio: make Reader.Reset and Writer.Reset work on the zero value
+ 2021-09-10 cf2fe5d6f1 doc/asm: fix HTML markup
+ 2021-09-10 1bf2cd1291 debug/elf: retain original error message when getSymbols fails.
+ 2021-09-10 5a4b9f9494 time: reference -tags=timetzdata in testing panic
+ 2021-09-10 025308fe08 testing: increase alternation precedence
+ 2021-09-10 5a94a90d84 cmd/compile/internal/types2: better error message for invalid array decls
+ 2021-09-10 da1aa65053 cmd/compile/internal/syntax: correct follow token for type parameter lists
+ 2021-09-10 96ab854ab0 cmd/compile/internal: better AST line highlight in ssa.html
+ 2021-09-10 90c5660616 embed: guarantee the returned file of FS.Open implements io.Seeker
+ 2021-09-10 c69f5c0d76 cmd/compile: add support for Abs and Copysign intrinsics on riscv64
+ 2021-09-10 2091bd3f26 cmd/compile: simiplify arm64 bitfield optimizations
+ 2021-09-09 b32209d22d cmd/compile: fix test case for unified IR (fix build)
+ 2021-09-09 1a708bcf1d cmd/compile: don't crash while reporting invalid alias cycle
+ 2021-09-09 426ff3746f cmd/cgo, runtime/cgo: avoid GCC/clang conversion warnings
+ 2021-09-09 73483df406 cmd/compile/internal/syntax: better error message for missing type constraint
+ 2021-09-09 e1c3f2158f time: propagate "," separator for fractional seconds into Format
+ 2021-09-09 c981874a5a cmd/compile: fix implement for closure in a global assignment
+ 2021-09-09 2c4f389c02 cmd/link: enable internal linker in more cases for ppc64le
+ 2021-09-09 fb84e99eb7 test: add compiler regress tests for #46461
+ 2021-09-09 b9e1a24581 cmd/compile: fix case where init info of OAS node is dropped
+ 2021-09-09 f9271e4f85 go/types, types2: rename RParams -> RecvTypeParams
+ 2021-09-09 ea434450c2 reflect: add hooks for dealing with narrow width floats
+ 2021-09-09 a53e3d5f88 net: deprecate (net.Error).Temporary
+ 2021-09-09 19457a58e5 cmd/compile: stenciled conversions might be NOPs
+ 2021-09-09 a295b3cec8 test: re-enable AsmCheck tests for types2-based frontends
+ 2021-09-09 66f0d35f71 go/types: reduce number of delayed functions
+ 2021-09-09 d2a77f1c76 go/types: handle recursive type parameter constraints
+ 2021-09-09 9e1eea6f8b go/types: detect constraint type inference cycles
+ 2021-09-09 b86e8dd0f3 test/typeparam: fix issue48094b test build
+ 2021-09-09 c84f3a4004 syscall: drop fallback to pipe in Pipe on linux/arm
+ 2021-09-09 376a079762 cmd/compile: fix unified IR panic when expanding nested inline function
+ 2021-09-09 6edc57983a internal/poll: report open fds when TestSplicePipePool fails
+ 2021-09-09 2481f6e367 cmd/compile: fix wrong instantiated type for embedded receiver
+ 2021-09-09 d62866ef79 cmd/compile: move checkptr alignment to SSA generation
+ 2021-09-09 8fad81cd62 cmd/compile: fold handling OCONV logic to separate function
+ 2021-09-09 9cbc76bdf9 cmd/internal/obj/arm64: add checks for incorrect use of REGTMP register
+ 2021-09-09 42563f89d7 cmd/compile: remove 'ext' fields from unified IR reader/writer types
+ 2021-09-09 4c52eac49b cmd/compile: simplify value coding for unified IR
+ 2021-09-09 e30a09013b cmd/compile: extrapolate $GOROOT in unified IR
+ 2021-09-08 a1f6208e56 go/types, types2: add Environment to Config
+ 2021-09-08 f5f8a911d8 cmd/compile/internal/types2: spell out 'Type' in type parameter APIs
+ 2021-09-08 bff39cf6cb cmd/compile: add automated rewrite cycle detection
+ 2021-09-08 b61e1ed863 cmd/compile/internal/types2: temporarily pin the Checker to Interface during checking
+ 2021-09-08 47f3e1e02c cmd/compile/internal/types2: move NewTypeParam off of Checker
+ 2021-09-08 ccc927b8f6 cmd/compile/internal/types2: move typeHash to environment.go
+ 2021-09-08 30e9bfbcef cmd/compile/internal/types2: implement deduplication of instances using the Environment
+ 2021-09-08 0406d3a8e5 go/ast: rename MultiIndexExpr to IndexListExpr

Change-Id: I7f917d45b0507c122c212305144b0b455618ff54

1 files changed, 25 insertions, 44 deletions

diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 4f9d76d598..16aafd622e 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -8,9 +8,6 @@ package types
 
 import "go/token"
 
-// TODO(rFindley) decide error codes for the errors in this file, and check
-//                if error spans can be improved
-
 type substMap map[*TypeParam]Type
 
 // makeSubstMap creates a new substitution map mapping tpars[i] to targs[i].
@@ -55,25 +52,12 @@ func (check *Checker) subst(pos token.Pos, typ Type, smap substMap, env *Environ
 	}
 
 	// general case
-	var subst subster
-	subst.pos = pos
-	subst.smap = smap
-
-	if check != nil {
-		subst.check = check
-		if env == nil {
-			env = check.env
-		}
+	subst := subster{
+		pos:   pos,
+		smap:  smap,
+		check: check,
+		env:   check.bestEnv(env),
 	}
-	if env == nil {
-		// If we don't have a *Checker and its global type map,
-		// use a local version. Besides avoiding duplicate work,
-		// the type map prevents infinite recursive substitution
-		// for recursive types (example: type T[P any] *T[P]).
-		env = NewEnvironment()
-	}
-	subst.env = env
-
 	return subst.typ(typ)
 }
 
@@ -128,8 +112,7 @@ func (subst *subster) typ(typ Type) Type {
 		if recv != t.recv || params != t.params || results != t.results {
 			return &Signature{
 				rparams: t.rparams,
-				// TODO(rFindley) why can't we nil out tparams here, rather than in
-				//                instantiate above?
+				// TODO(rFindley) why can't we nil out tparams here, rather than in instantiate?
 				tparams:  t.tparams,
 				scope:    t.scope,
 				recv:     recv,
@@ -182,13 +165,19 @@ func (subst *subster) typ(typ Type) Type {
 			}
 		}
 
-		if t.TypeParams().Len() == 0 {
+		// subst is called by expandNamed, so in this function we need to be
+		// careful not to call any methods that would cause t to be expanded: doing
+		// so would result in deadlock.
+		//
+		// So we call t.orig.TypeParams() rather than t.TypeParams() here and
+		// below.
+		if t.orig.TypeParams().Len() == 0 {
 			dump(">>> %s is not parameterized", t)
 			return t // type is not parameterized
 		}
 
 		var newTArgs []Type
-		assert(t.targs.Len() == t.TypeParams().Len())
+		assert(t.targs.Len() == t.orig.TypeParams().Len())
 
 		// already instantiated
 		dump(">>> %s already instantiated", t)
@@ -201,7 +190,7 @@ func (subst *subster) typ(typ Type) Type {
 			if new_targ != targ {
 				dump(">>> substituted %d targ %s => %s", i, targ, new_targ)
 				if newTArgs == nil {
-					newTArgs = make([]Type, t.TypeParams().Len())
+					newTArgs = make([]Type, t.orig.TypeParams().Len())
 					copy(newTArgs, t.targs.list())
 				}
 				newTArgs[i] = new_targ
@@ -221,27 +210,19 @@ func (subst *subster) typ(typ Type) Type {
 			return named
 		}
 
-		// Create a new named type and populate the environment to avoid endless
+		t.orig.resolve(subst.env)
+		// Create a new instance and populate the environment to avoid endless
 		// recursion. The position used here is irrelevant because validation only
 		// occurs on t (we don't call validType on named), but we use subst.pos to
 		// help with debugging.
-		tname := NewTypeName(subst.pos, t.obj.pkg, t.obj.name, nil)
-		t.load()
-		// 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 = NewTypeList(newTArgs)
-		subst.env.typeForHash(h, named)
-		t.expand(subst.env) // must happen after env update to avoid infinite recursion
-
-		// do the substitution
-		dump(">>> subst %s with %s (new: %s)", t.underlying, subst.smap, newTArgs)
-		named.underlying = subst.typOrNil(t.underlying)
-		dump(">>> underlying: %v", named.underlying)
-		assert(named.underlying != nil)
-		named.fromRHS = named.underlying // for consistency, though no cycle detection is necessary
-
-		return named
+		t.orig.resolve(subst.env)
+		return subst.check.instance(subst.pos, t.orig, newTArgs, subst.env)
+
+		// Note that if we were to expose substitution more generally (not just in
+		// the context of a declaration), we'd have to substitute in
+		// named.underlying as well.
+		//
+		// But this is unnecessary for now.
 
 	case *TypeParam:
 		return subst.smap.lookup(t)