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 43ad4ee67f95c0c19490b58c237bf5bf3124d0c5..d262ab9f851ffcdf98cce227950ce264f3abd225 100644 (file)
--- 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 823d940d9bca0d41ded1e557e3d6d05d1dca06f4..bedcc4c0150aa65d549c8c2c7ea7170fe1384200 100644 (file)
--- 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 a60a1adfd9b608d0b67e8a344d02b2d71f2590d6..77bff811b92ae72d14c690815cd525966dfff29d 100644 (file)
--- 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 360cb4deb0ef46465755d84cd4eff6aa86b15dc7..742191cc1c9e6e3098b2b83561cb12e0669dfe76 100644 (file)
--- 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