Index: include/clang/Sema/Scope.h
===================================================================
--- include/clang/Sema/Scope.h
+++ include/clang/Sema/Scope.h
@@ -124,6 +124,9 @@
 
     /// We are currently in the filter expression of an SEH except block.
     SEHFilterScope = 0x200000,
+
+    /// This is a compound statement scope.
+    CompoundStmtScope = 0x400000,
   };
 private:
   /// The parent scope for this scope.  This is null for the translation-unit
@@ -429,6 +432,9 @@
   /// \brief Determine whether this scope is a SEH '__except' block.
   bool isSEHExceptScope() const { return getFlags() & Scope::SEHExceptScope; }
 
+  /// \brief Determine whether this scope is a compound statement scope.
+  bool isCompoundStmtScope() const { return getFlags() & Scope::CompoundStmtScope; }
+
   /// \brief Returns if rhs has a higher scope depth than this.
   ///
   /// The caller is responsible for calling this only if one of the two scopes
Index: lib/Parse/ParseStmt.cpp
===================================================================
--- lib/Parse/ParseStmt.cpp
+++ lib/Parse/ParseStmt.cpp
@@ -840,7 +840,8 @@
 }
 
 StmtResult Parser::ParseCompoundStatement(bool isStmtExpr) {
-  return ParseCompoundStatement(isStmtExpr, Scope::DeclScope);
+  return ParseCompoundStatement(isStmtExpr,
+                                Scope::DeclScope | Scope::CompoundStmtScope);
 }
 
 /// ParseCompoundStatement - Parse a "{}" block.
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -12605,12 +12605,16 @@
                 SourceLocation());
   D.SetIdentifier(&II, Loc);
 
-  // Insert this function into translation-unit scope.
+  // Insert this function into the enclosing block scope.
+  while (S && !S->isCompoundStmtScope() && !S->isFunctionScope())
+    S = S->getParent();
+  if (S == nullptr)
+    S = TUScope;
 
   DeclContext *PrevDC = CurContext;
   CurContext = Context.getTranslationUnitDecl();
 
-  FunctionDecl *FD = cast<FunctionDecl>(ActOnDeclarator(TUScope, D));
+  FunctionDecl *FD = cast<FunctionDecl>(ActOnDeclarator(S, D));
   FD->setImplicit();
 
   CurContext = PrevDC;
Index: test/Sema/implicit-decl-c90.c
===================================================================
--- /dev/null
+++ test/Sema/implicit-decl-c90.c
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 %s -std=c90 -verify -fsyntax-only
+void t0(int x) {
+  int (*p)();
+  if(x > 0)
+    x = g() + 1;
+  p = g;
+  if(x < 0) {
+    extern void u(int (*)[h()]);
+    int (*q)() = h;
+  }
+  p = h; /* expected-error {{use of undeclared identifier 'h'}} */
+}
+
+void t1(int x) {
+  int (*p)();
+  switch (x) {
+    g();
+  case 0:
+    x = h() + 1;
+    break;
+  case 1:
+    p = g;
+    p = h;
+    break;
+  }
+  p = g; /* expected-error {{use of undeclared identifier 'g'}} */
+  p = h; /* expected-error {{use of undeclared identifier 'h'}} */
+}
+
+int (*p)() = g; /* expected-error {{use of undeclared identifier 'g'}} */
+int (*q)() = h; /* expected-error {{use of undeclared identifier 'h'}} */
+
+float g(); /* not expecting conflicting types diagnostics here */
Index: test/Sema/implicit-decl.c
===================================================================
--- test/Sema/implicit-decl.c
+++ test/Sema/implicit-decl.c
@@ -9,8 +9,7 @@
    int32_t *vector[16];
    const char compDesc[16 + 1];
    int32_t compCount = 0;
-   if (_CFCalendarDecomposeAbsoluteTimeV(compDesc, vector, compCount)) { // expected-note {{previous implicit declaration is here}} \
-         expected-error {{implicit declaration of function '_CFCalendarDecomposeAbsoluteTimeV' is invalid in C99}}
+   if (_CFCalendarDecomposeAbsoluteTimeV(compDesc, vector, compCount)) { // expected-error {{implicit declaration of function '_CFCalendarDecomposeAbsoluteTimeV' is invalid in C99}}
    }
 
    printg("Hello, World!\n"); // expected-error{{implicit declaration of function 'printg' is invalid in C99}} \
@@ -18,7 +17,7 @@
 
   __builtin_is_les(1, 3); // expected-error{{use of unknown builtin '__builtin_is_les'}}
 }
-Boolean _CFCalendarDecomposeAbsoluteTimeV(const char *componentDesc, int32_t **vector, int32_t count) { // expected-error{{conflicting types for '_CFCalendarDecomposeAbsoluteTimeV'}}
+Boolean _CFCalendarDecomposeAbsoluteTimeV(const char *componentDesc, int32_t **vector, int32_t count) {
  return 0;
 }