[dev.regabi] cmd/compile: reshuffle type-checking code [generated]

This commit splits up typecheck.Package and moves the code
elsewhere. The type-checking code is moved into noder, so that it can
eventually be interleaved with the noding process. The
non-type-checking code is moved back into package gc, so that it can
be incorporated into appropriate compiler backend phases.

While here, deadcode removal is moved into its own package.

Passes toolstash -cmp.

[git-generate]
cd src/cmd/compile/internal/typecheck

: Split into two functions.
sed -i -e '/Phase 6/i}\n\nfunc postTypecheck() {' typecheck.go

rf '
	# Export needed identifiers.
	mv deadcode Deadcode
	mv loadsys InitRuntime
	mv declareUniverse DeclareUniverse
	mv dirtyAddrtaken DirtyAddrtaken
	mv computeAddrtaken ComputeAddrtaken
	mv incrementalAddrtaken IncrementalAddrtaken

	# Move into new package.
	mv Deadcode deadcodeslice deadcodeexpr deadcode.go
	mv deadcode.go cmd/compile/internal/deadcode

	# Move top-level type-checking code into noder.
	# Move DeclVars there too, now that nothing else uses it.
	mv DeclVars Package noder.go
	mv noder.go cmd/compile/internal/noder

	# Move non-type-checking code back into gc.
	mv postTypecheck main.go
	mv main.go cmd/compile/internal/gc
'

cd ../deadcode
rf '
	# Destutter names.
	mv Deadcode Func
	mv deadcodeslice stmts
	mv deadcodeexpr expr
'

cd ../noder
rf '
	# Move functions up, next to their related code.
	mv noder.go:/func Package/-1,$ \
		noder.go:/makeSrcPosBase translates/-1
	mv noder.go:/func DeclVars/-3,$ \
		noder.go:/constState tracks/-1
'

cd ../gc
rf '
	# Inline postTypecheck code back into gc.Main.
	mv main.go:/func postTypecheck/+0,/AllImportedBodies/+1 \
		main.go:/Build init task/-1
	rm postTypecheck
'

Change-Id: Ie5e992ece4a42204cce6aa98dd6eb52112d098c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/280974
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

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

@@ -85,6 +85,69 @@ func ParseFiles(filenames []string) uint {
 	return lines
 }
 
+func Package() {
+	typecheck.DeclareUniverse()
+
+	typecheck.TypecheckAllowed = true
+
+	// Process top-level declarations in phases.
+
+	// Phase 1: const, type, and names and types of funcs.
+	//   This will gather all the information about types
+	//   and methods but doesn't depend on any of it.
+	//
+	//   We also defer type alias declarations until phase 2
+	//   to avoid cycles like #18640.
+	//   TODO(gri) Remove this again once we have a fix for #25838.
+
+	// Don't use range--typecheck can add closures to Target.Decls.
+	base.Timer.Start("fe", "typecheck", "top1")
+	for i := 0; i < len(typecheck.Target.Decls); i++ {
+		n := typecheck.Target.Decls[i]
+		if op := n.Op(); op != ir.ODCL && op != ir.OAS && op != ir.OAS2 && (op != ir.ODCLTYPE || !n.(*ir.Decl).X.Alias()) {
+			typecheck.Target.Decls[i] = typecheck.Stmt(n)
+		}
+	}
+
+	// Phase 2: Variable assignments.
+	//   To check interface assignments, depends on phase 1.
+
+	// Don't use range--typecheck can add closures to Target.Decls.
+	base.Timer.Start("fe", "typecheck", "top2")
+	for i := 0; i < len(typecheck.Target.Decls); i++ {
+		n := typecheck.Target.Decls[i]
+		if op := n.Op(); op == ir.ODCL || op == ir.OAS || op == ir.OAS2 || op == ir.ODCLTYPE && n.(*ir.Decl).X.Alias() {
+			typecheck.Target.Decls[i] = typecheck.Stmt(n)
+		}
+	}
+
+	// Phase 3: Type check function bodies.
+	// Don't use range--typecheck can add closures to Target.Decls.
+	base.Timer.Start("fe", "typecheck", "func")
+	var fcount int64
+	for i := 0; i < len(typecheck.Target.Decls); i++ {
+		n := typecheck.Target.Decls[i]
+		if n.Op() == ir.ODCLFUNC {
+			typecheck.FuncBody(n.(*ir.Func))
+			fcount++
+		}
+	}
+
+	// Phase 4: Check external declarations.
+	// TODO(mdempsky): This should be handled when type checking their
+	// corresponding ODCL nodes.
+	base.Timer.Start("fe", "typecheck", "externdcls")
+	for i, n := range typecheck.Target.Externs {
+		if n.Op() == ir.ONAME {
+			typecheck.Target.Externs[i] = typecheck.Expr(typecheck.Target.Externs[i])
+		}
+	}
+
+	// Phase 5: With all user code type-checked, it's now safe to verify map keys.
+	typecheck.CheckMapKeys()
+
+}
+
 // makeSrcPosBase translates from a *syntax.PosBase to a *src.PosBase.
 func (p *noder) makeSrcPosBase(b0 *syntax.PosBase) *src.PosBase {
 	// fast path: most likely PosBase hasn't changed
@@ -398,7 +461,61 @@ func (p *noder) varDecl(decl *syntax.VarDecl) []ir.Node {
 	}
 
 	p.setlineno(decl)
-	return typecheck.DeclVars(names, typ, exprs)
+	return DeclVars(names, typ, exprs)
+}
+
+// declare variables from grammar
+// new_name_list (type | [type] = expr_list)
+func DeclVars(vl []*ir.Name, t ir.Ntype, el []ir.Node) []ir.Node {
+	var init []ir.Node
+	doexpr := len(el) > 0
+
+	if len(el) == 1 && len(vl) > 1 {
+		e := el[0]
+		as2 := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+		as2.Rhs = []ir.Node{e}
+		for _, v := range vl {
+			as2.Lhs.Append(v)
+			typecheck.Declare(v, typecheck.DeclContext)
+			v.Ntype = t
+			v.Defn = as2
+			if ir.CurFunc != nil {
+				init = append(init, ir.NewDecl(base.Pos, ir.ODCL, v))
+			}
+		}
+
+		return append(init, as2)
+	}
+
+	for i, v := range vl {
+		var e ir.Node
+		if doexpr {
+			if i >= len(el) {
+				base.Errorf("assignment mismatch: %d variables but %d values", len(vl), len(el))
+				break
+			}
+			e = el[i]
+		}
+
+		typecheck.Declare(v, typecheck.DeclContext)
+		v.Ntype = t
+
+		if e != nil || ir.CurFunc != nil || ir.IsBlank(v) {
+			if ir.CurFunc != nil {
+				init = append(init, ir.NewDecl(base.Pos, ir.ODCL, v))
+			}
+			as := ir.NewAssignStmt(base.Pos, v, e)
+			init = append(init, as)
+			if e != nil {
+				v.Defn = as
+			}
+		}
+	}
+
+	if len(el) > len(vl) {
+		base.Errorf("assignment mismatch: %d variables but %d values", len(vl), len(el))
+	}
+	return init
 }
 
 // constState tracks state between constant specifiers within a