From 8b2a22fb47ad5f97ece29fc3ce81e689ed096387 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 9 May 2020 23:58:22 +0900
Subject: [PATCH] shader: Parse return

---
 internal/shader/block.go       | 60 ++++++++++++++++++++++++++++++++++
 internal/shader/shader.go      | 21 +++++++++++-
 internal/shader/shader_test.go |  7 ++--
 3 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/internal/shader/block.go b/internal/shader/block.go
index 207eaa1d4..7060809d8 100644
--- a/internal/shader/block.go
+++ b/internal/shader/block.go
@@ -35,8 +35,68 @@ func (b *block) dump(indent int) []string {
 		lines = append(lines, fmt.Sprintf("%svar %s %s", idt, v.name, v.typ))
 	}
 
+	for _, s := range b.stmts {
+		lines = append(lines, s.dump(indent)...)
+	}
+
 	return lines
 }
 
+type stmtType int
+
+const (
+	stmtNone stmtType = iota
+	stmtReturn
+)
+
 type stmt struct {
+	stmtType stmtType
+	exprs    []expr
+}
+
+func (s *stmt) dump(indent int) []string {
+	idt := strings.Repeat("\t", indent)
+
+	var lines []string
+	switch s.stmtType {
+	case stmtNone:
+		lines = append(lines, "%s(none)", idt)
+	case stmtReturn:
+		var expr string
+		if len(s.exprs) > 0 {
+			var strs []string
+			for _, e := range s.exprs {
+				strs = append(strs, e.dump())
+			}
+			expr = " " + strings.Join(strs, ", ")
+		}
+		lines = append(lines, fmt.Sprintf("%sreturn%s", idt, expr))
+	default:
+		lines = append(lines, fmt.Sprintf("%s(unknown stmt: %d)", idt, s.stmtType))
+	}
+
+	return lines
+}
+
+type exprType int
+
+const (
+	exprNone exprType = iota
+	exprIdent
+)
+
+type expr struct {
+	exprType exprType
+	value    string
+}
+
+func (e *expr) dump() string {
+	switch e.exprType {
+	case exprNone:
+		return "(none)"
+	case exprIdent:
+		return e.value
+	default:
+		return fmt.Sprintf("(unkown expr: %d)", e.exprType)
+	}
 }
diff --git a/internal/shader/shader.go b/internal/shader/shader.go
index 5c71ccd94..4c5e3e7b7 100644
--- a/internal/shader/shader.go
+++ b/internal/shader/shader.go
@@ -248,7 +248,7 @@ func (s *Shader) parseTopLevelConstant(vs *ast.ValueSpec) {
 				s.addError(v.Pos(), fmt.Sprintf("literal must be int or float but %s", v.Kind))
 				return
 			}
-			init = v.Value // TODO: This should be math/big.Int or Float.
+			init = v.Value // TODO: This should be go/constant.Value
 		default:
 			// TODO: Parse the expression.
 		}
@@ -348,6 +348,14 @@ func (sh *Shader) parseBlock(b *ast.BlockStmt) *block {
 				}
 			}
 		case *ast.ReturnStmt:
+			var exprs []expr
+			for _, r := range l.Results {
+				exprs = append(exprs, sh.parseExpr(r))
+			}
+			block.stmts = append(block.stmts, stmt{
+				stmtType: stmtReturn,
+				exprs:    exprs,
+			})
 		default:
 		}
 	}
@@ -359,6 +367,17 @@ func (sh *Shader) parseBlock(b *ast.BlockStmt) *block {
 	return block
 }
 
+func (sh *Shader) parseExpr(e ast.Expr) expr {
+	switch e := e.(type) {
+	case *ast.Ident:
+		return expr{
+			exprType: exprIdent,
+			value:    e.Name,
+		}
+	}
+	return expr{}
+}
+
 // Dump dumps the shader state in an intermediate language.
 func (s *Shader) Dump() string {
 	var lines []string
diff --git a/internal/shader/shader_test.go b/internal/shader/shader_test.go
index ed5ad2669..fc7c66be2 100644
--- a/internal/shader/shader_test.go
+++ b/internal/shader/shader_test.go
@@ -46,8 +46,9 @@ const C2, C3 float = 2, 3
 
 func F1(a, b vec2) vec4 {
 	var c0 vec2 = a
-	var c1 = b
-	c2 := vec4{c0, c1}
+	var c1, c2 = b, 1.0
+	c1.x = c2.x
+	c3 := vec4{c0, c1}
 	return c2
 }
 `,
@@ -66,6 +67,8 @@ func F1(a vec2, b vec2) (_ vec4) {
 	var c0 vec2
 	var c1 (none)
 	var c2 (none)
+	var c3 (none)
+	return c2
 }
 `,
 		},