From: Mark Freeman <mark@golang.org>
Date: Thu, 10 Apr 2025 15:27:29 +0000 (-0400)
Subject: go/types, types2: set up recording of positions for declarations
X-Git-Tag: go1.25rc1~361
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=5e7f0b947c3907bd23a13864c3fea2b204f11567;p=gostls13.git

go/types, types2: set up recording of positions for declarations

This creates the infrastructure needed to record compiler panics
induced somewhere beneath a declaration. For now, this is turned
off via a flag.

This does not yet use the position information for better error
messages. That is moved off to a separate CL.

Change-Id: I6b44135a84ebd2f4c0141408ba9228d72c497d55
Reviewed-on: https://go-review.googlesource.com/c/go/+/664475
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Mark Freeman <mark@golang.org>
Auto-Submit: Mark Freeman <mark@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---

diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index 43ad4ee67f..d262ab9f85 100644
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -20,6 +20,9 @@ var nopos syntax.Pos
 // debugging/development support
 const debug = false // leave on during development
 
+// position tracing for panics during type checking
+const tracePos = false // TODO(markfreeman): check performance implications
+
 // _aliasAny changes the behavior of [Scope.Lookup] for "any" in the
 // [Universe] scope.
 //
@@ -178,7 +181,8 @@ type Checker struct {
 	environment
 
 	// debugging
-	indent int // indentation for tracing
+	posStack []syntax.Pos // stack of source positions seen; used for panic tracing
+	indent   int          // indentation for tracing
 }
 
 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
@@ -396,6 +400,16 @@ func versionMax(a, b goVersion) goVersion {
 	return b
 }
 
+// pushPos pushes pos onto the pos stack.
+func (check *Checker) pushPos(pos syntax.Pos) {
+	check.posStack = append(check.posStack, pos)
+}
+
+// popPos pops from the pos stack.
+func (check *Checker) popPos() {
+	check.posStack = check.posStack[:len(check.posStack)-1]
+}
+
 // A bailout panic is used for early termination.
 type bailout struct{}
 
@@ -405,6 +419,7 @@ func (check *Checker) handleBailout(err *error) {
 		// normal return or early exit
 		*err = check.firstErr
 	default:
+		// TODO(markfreeman): dump posStack if available
 		// re-panic
 		panic(p)
 	}
diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 823d940d9b..bedcc4c015 100644
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -48,6 +48,17 @@ func pathString(path []Object) string {
 // objDecl type-checks the declaration of obj in its respective (file) environment.
 // For the meaning of def, see Checker.definedType, in typexpr.go.
 func (check *Checker) objDecl(obj Object, def *TypeName) {
+	if tracePos {
+		check.pushPos(obj.Pos())
+		defer func() {
+			// If we're panicking, keep stack of source positions.
+			if p := recover(); p != nil {
+				panic(p)
+			}
+			check.popPos()
+		}()
+	}
+
 	if check.conf.Trace && obj.Type() == nil {
 		if check.indent == 0 {
 			fmt.Println() // empty line between top-level objects for readability
diff --git a/src/go/types/check.go b/src/go/types/check.go
index a60a1adfd9..77bff811b9 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -23,6 +23,9 @@ var noposn = atPos(nopos)
 // debugging/development support
 const debug = false // leave on during development
 
+// position tracing for panics during type checking
+const tracePos = false // TODO(markfreeman): check performance implications
+
 // gotypesalias controls the use of Alias types.
 // As of Apr 16 2024 they are used by default.
 // To disable their use, set GODEBUG to gotypesalias=0.
@@ -198,7 +201,8 @@ type Checker struct {
 	environment
 
 	// debugging
-	indent int // indentation for tracing
+	posStack []positioner // stack of source positions seen; used for panic tracing
+	indent   int          // indentation for tracing
 }
 
 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
@@ -421,6 +425,16 @@ func versionMax(a, b goVersion) goVersion {
 	return a
 }
 
+// pushPos pushes pos onto the pos stack.
+func (check *Checker) pushPos(pos positioner) {
+	check.posStack = append(check.posStack, pos)
+}
+
+// popPos pops from the pos stack.
+func (check *Checker) popPos() {
+	check.posStack = check.posStack[:len(check.posStack)-1]
+}
+
 // A bailout panic is used for early termination.
 type bailout struct{}
 
@@ -430,6 +444,7 @@ func (check *Checker) handleBailout(err *error) {
 		// normal return or early exit
 		*err = check.firstErr
 	default:
+		// TODO(markfreeman): dump posStack if available
 		// re-panic
 		panic(p)
 	}
diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 360cb4deb0..742191cc1c 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -49,6 +49,17 @@ func pathString(path []Object) string {
 // objDecl type-checks the declaration of obj in its respective (file) environment.
 // For the meaning of def, see Checker.definedType, in typexpr.go.
 func (check *Checker) objDecl(obj Object, def *TypeName) {
+	if tracePos {
+		check.pushPos(atPos(obj.Pos()))
+		defer func() {
+			// If we're panicking, keep stack of source positions.
+			if p := recover(); p != nil {
+				panic(p)
+			}
+			check.popPos()
+		}()
+	}
+
 	if check.conf._Trace && obj.Type() == nil {
 		if check.indent == 0 {
 			fmt.Println() // empty line between top-level objects for readability